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THC levels
- Thread starter JWP
- Start date
G
Guest
did i say cannabinoids or cannabis...it truly is a waist of your time...you cant even read what i posted...
Sam_Skunkman said:
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G
Guest
maybee i will post this liitle bit again..just for you sam..peace
Cannabinoid receptors have been studied most in vertebrates, such as rats and mice. However, they are also found in invertebrates, such as leeches and mollusks.156 The evolutionary history of vertebrates and invertebrates diverged more than 500 million years ago, so cannabinoid receptors appear to have been conserved throughout evolution at least this long. This suggests that they serve an important and basic function in animal physiology. In general, cannabinoid receptor molecules are similar among different species.124 Thus, cannabinoid receptors likely fill many similar functions in a broad range of animals, including humans.
Cannabinoid receptors have been studied most in vertebrates, such as rats and mice. However, they are also found in invertebrates, such as leeches and mollusks.156 The evolutionary history of vertebrates and invertebrates diverged more than 500 million years ago, so cannabinoid receptors appear to have been conserved throughout evolution at least this long. This suggests that they serve an important and basic function in animal physiology. In general, cannabinoid receptor molecules are similar among different species.124 Thus, cannabinoid receptors likely fill many similar functions in a broad range of animals, including humans.
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G
Guest
a little history on our beloved plant...peace
The Marijuana, cannabis, or hemp plant is one of the oldest psychoactive plants known to humanity. Cannabis has become one of the most widespread and diversified of plants. It grows as weed and cultivated plant all over the world in a variety of climates and soils. Cannabis preparations have been used as remedies for thousands of years and the active ingredients of the hemp plant can be put to use in a multitude of medical conditions.
Marijuana has been used throughout history in many different cultures to change mood, perception, and consciousness - in other words, to get high. Its effects range from increasing creativity to provoking mystical experiences, to heightening the capacity to feel, sense and share. After alcohol, it is the most popular of what are called "recreational drugs."
6000 B.C. Cannabis seeds used for food in China
4000 B.C. Textiles made of hemp are used in China. Remains have been found of hemp fibers from this period and from Turkestan a century later. 1
2727 B.C. First recorded use of cannabis as medicine in Chinese pharmacopoeia. In every part of the world humankind has used cannabis for a wide variety of health problems. 2
1500 B.C. Cannabis cultivated in China for food and fiber
1500 B.C. Scythians cultivate cannabis and use it to weave fine hemp cloth. (Sumach 1975)
1200 - 800 BCE Bhang (dried cannabis leaves, seeds and stems) is mentioned in the Hindu sacred text Atharva veda (Science of Charms) as "Sacred Grass", one of the five sacred plants of India. It is used by medicinally and ritually as an offering to Shiva. 3
700 - 600 BCE The Zoroastrian Zend-Avesta, an ancient Persian religious text of several hundred volumes, and said to have been written by Zarathustra (Zoroaster), refers to bhang as Zoroaster's "good narcotic" (Vendidad or The Law Against Demons)
700 - 300 BCE Scythian tribes leave Cannabis seeds as offerings in royal tombs.
500 B.C. Scythian couple die and are buried with two small tents covering censers. Attached to one tent stick was a decorated leather pouch containing wild Cannabis seeds. This closely matches the stories told by Herodotus. The gravesite, discovered in the late 1940s, was in Pazryk, northwest of the Tien Shan Mountains in modern-day Khazakstan.
500 B.C. Hemp is introduced into Northern Europe by the Scythians. An urn containing leaves and seeds of the Cannabis plant, unearthed near Berlin, is dated to about this time.
500 - 100 BCE Hemp spreads throughout northern Europe.
430 B.C. Herodotus reports on both ritual and recreation use of Cannabis by the Scythians (Herodotus The Histories 430 B.C. trans. G. Rawlinson).
100 - 0 BCE The psychotropic properties of Cannabis are mentioned in the newly compiled herbal Pen Ts'ao Ching which is attributed to an emperor c. 2700 B.C.
0 - 100 A.D. Construction of Samartian gold and glass paste stash box for storing hashish, coriander, or salt, buried in Siberian tomb.
70 Dioscorides mentions the use of Cannabis as a Roman medicament.
170 Galen (Roman) alludes to the psychoactivity of Cannabis seed confections.
500 - 600 The Jewish Talmud mentions the euphoriant properties of Cannabis. (Abel 1980)
900 - 1000 Scholars debate the pros and cons of eating hashish. Use spreads throughout Arabia.
1090 - 1256 In Khorasan, Persia, Hasan ibn al-Sabbah, the Old Man of the Mountain, recruits followers to commit assassinations...legends develop around their supposed use of hashish. These legends are some of the earliest written tales of the discovery of the inebriating powers of Cannabis and the supposed use of Hashish. 1256 Alamut falls
Early 12th Century Hashish smoking very popular throughout the Middle East.
12th Century Cannabis is introduced in Egypt during the reign of the Ayyubid dynasty on the occasion of the flooding of Egypt by mystic devotees coming from Syria. (M.K. Hussein 1957 - Soueif 1972)
1155 - 1221 Persian legend of the Sufi master Sheik Haidar's of Khorasan's personal discovery of Cannabis and it's subsequent spread to Iraq, Bahrain, Egypt and Syria. Another of the ealiest written narratives of the use of Cannabis as an inebriant.
13th Century The oldest monograph on hashish, Zahr al-'arish fi tahrim al-hashish, was written. It has since been lost.
13th Century Ibn al-Baytar of Spain provides a description of psychaoctive Cannabis.
13th Century Arab traders bring Cannabis to the Mozambique coast of Africa.
1231 Hashish introduced to Iraq in the reign of Caliph Mustansir (Rosenthal 1971)
1271 - 1295 Journeys of Marco Polo in which he gives second-hand reports of the story of Hasan ibn al-Sabbah and his "assassins" using hashish. First time reports of Cannabis have been brought to the attention of Europe.
1378 Ottoman Emir Soudoun Scheikhouni issues one of the first edicts against the eating of hashish.
1526 Babur Nama, first emperor and founder of Mughal Empire learned of hashish in Afghanistan.
1549 Angolan slaves brought cannabis with them to the sugar plantations of northeastern Brazil. They were permitted to plant their cannabis between rows of cane, and to smoke it between harvests. 3
mid 16th Century The epic poem, Benk u Bode, by the poet Mohammed Ebn Soleiman Foruli of Baghdad, deals allegorically with a dialectical battle between wine and hashish.
17th Century Use of hashish, alcohol, and opium spreads among the population of occupied Constantinople
1606-1632 French and British cultivate Cannabis for hemp at their colonies in Port Royal (1606), Virginia (1611), and Plymouth (1632). 3
Late 17th Century Hashish becomes a major trade item between Central Asia and South Asia.
1798 Napoleon discovers that much of the Egyptian lower class habitually uses hashish (Kimmens 1977). He declares a total prohibition. Soldiers returning to France bring the tradition with them.
19th Century Hashish production expands from Russian Turkestan into Yarkand in Chinese Turkestan.
1809 Antoine Sylvestre de Sacy, a leading Arabist, reveals the etymology of the words "assassin" and "hashishin"
1840 In America, medicinal preparations with a Cannabis base are available. Hashish available in Persian pharmacies.
1840s Heydey of the Club des Hachichins in Paris. 3
1843 Le Club des Hachichins, or Hashish Eater's Club, established in Paris.
after 1850 Hashish appears in Greece.
1856 British tax ganja and charas trade in India
1870 - 1880 First reports of hashish smoking on Greek mainland
c. 1875 Cultivation for hashish introduced to Greece
1877 Kerr reports on Indian ganja and charas trade.
1890 Greek Department of Interior prohibits importance, cultivation and use of hashish.
1890 Hashish made illegal in Turkey
1893 - 1894 The India Hemp Drugs Commission Report is issued.
1893 - 1894 70,000 to 80,000 kg of hashish legally imported into India from Central Asia each year.
1906 Pure Food and Drug Act is passed, regulating the labelling of products containing Alcohol, Opiates, Cocaine, and Cannabis, among others. The law went into effect Jan 1, 1907 4 [Details]
Early 20th Century Hashish smoking very popular throughout the Middle East.
1915 - 1927 Cannabis begins to be prohibited for nonmedical use in the U.S., especially in SW states...California (1915), Texas (1919), Louisiana (1924), and New York (1927).
1920 Metaxus dictators in Greece crack down on hashish smoking.
1920s Hashish smuggled into Egypt from Greece, Syria, Lebanon, Turkey, and Central Asia
1926 Lebanese hashish production peaks after World War I until prohibited in 1926.
1928 Recrational use of Cannabis is banned in Britain.
1920s - 1930s High-quality hashish produced in Turkey near Greek border.
1930 Yarkand region of Chinese Turkestan exports 91,471 kg of hashish legally into the Northwest Frontier and Punjab regions of India
1930s Legal taxed imports of hashish continue into India from Central Asia.
1934 - 1935 Chinese government moves to end all Cannabis cultivation in Yarkand and charas traffic from Yarkand. Both licit and illicit hashish production become illegal in Chinese Turkestan.
1936 Propaganda film "Reefer Madness" made to scare American youth away from using Cannabis.
1937 Cannabis made federally illegal in the U.S. with the passage of the Marihuana Tax Act.
1938 Supply of hashish from chinese Turkestan nearly ceases.
1940s Greek hashish smoking tradition fades.
1941 Indian government considers cultivation in Kashmir to fill void of hashish from Chinese Turkestan.
1941 - 1942 Hand-rubbed charas from Nepal is choicest hashish in India during World War II.
1945 Legal hashish consumption continues in India
1945 - 1955 Hashish use in Greece flourishes again
1950s Hashish still smuggled into India from Chinese Central Asia
1950s Moroccan government tacitly allows kif cultivation in Rif Mountains.
1962 First hashish made in Morocco.
1963 Turkish police seize 2.5 tons of hashish
1965 First reports of C. afghanica use for hashish production in northern Afghanistan
1965 Mustafa comes to Ketama in Morocco to make hashish from local kif.
1966 The Moroccan government attempts to purge kif growers from Rif Mountains.
1967 "Smash", the first hashish oil appears. Red Lebanese reaches California.
Late 1960s - Early 1970s The Brotherhood popularizes Afghani hashish.
1970 - 1973 Huge fields of Cannabis cultivated for hashish production in Afghanistan. Last years that truly great afghani hashish is available
1972 The Nixon-appointed Shafer Commission urged use of cannabis be re-legalized, but their recommendation was ignored. Medical research continues. 2
Early 1970s Lebanese red and blonde hashish of very high-quality exported. The highest quality Turkish hashish from Gaziantep near Syria appears in western Europe.
Early 1970s Afghani hashish varieties introduced to North America for sinsemilla production. Westerners bring metal sieve cloths to Afghanistan. Law enforcement efforts against hashish begin in Afghanistan
1973 Nepal bans the Cannabis shops and charas (hand-rolled hash) export.
1973 Afghan government makes hashish production and sales illegal. Afghani harvest is pitifully small.
1975 FDA establishes Compassionate Use program for medical marijuana.
1976 - 1977 Quality of Lebanese hashish reaches zenith.
1978 Westerners make sieved hashish in Nepal from wild Cannabis.
Late 1970s Increasing manufacture of "modern" Afghani hashish. Cannabis varieties from Afghanistan imported into Kashmir for sieved hashish production.
1980s Morocco becomes one of, if not the largest, hashish producing and exporting nations.
1980s "Border" hashish produced in northwestern Pakistan along the Afghan border to avoid Soviet-Afghan war.
Early 1980s Quality of Lebanese hashish declines.
1983 - 1984 Small amounts of the last high-quality Turkish hashish appear.
1985 Hashish still produced by Muslims of Kashgar and Yarkland (NW China).
1986 Most private stashes of pre-war Afghani hashish in Amsterdam, Goa, and America are nearly finished.
May 13, 1986 Dronabinol is placed into Schedule II by the DEA. 5
1987 Moroccan government cracks down upon Cannabis cultivation in lower eleations of Rif Mountains.
1988 DEA administrative law Judge Francis Young finds after thorough hearings that marijuana has clearly established medical use and should be reclassified as a prescriptive drug. His recommendation is ignored.
1993 Cannabis eradication efforts resume in Morocco.
1994 Heavy fighting between rival Muslim clans continues to upset hashish trade in Afghanistan
1994 Border hashish still produced in Pakistan.
1995 Introduction of hashish-making equipment and appearance of locally produced hashish in Amsterdam coffee shops.
Oct 23, 2001 Britain's Home Secretary, David Blunkett, proposes relaxing the classification of cannabis from a class B to class C. As of June 10, 2002, this has not taken effect. [More Info]
June 2003 Canada is first country in the world to offer medical marijuana to its patients.
The Marijuana, cannabis, or hemp plant is one of the oldest psychoactive plants known to humanity. Cannabis has become one of the most widespread and diversified of plants. It grows as weed and cultivated plant all over the world in a variety of climates and soils. Cannabis preparations have been used as remedies for thousands of years and the active ingredients of the hemp plant can be put to use in a multitude of medical conditions.
Marijuana has been used throughout history in many different cultures to change mood, perception, and consciousness - in other words, to get high. Its effects range from increasing creativity to provoking mystical experiences, to heightening the capacity to feel, sense and share. After alcohol, it is the most popular of what are called "recreational drugs."
6000 B.C. Cannabis seeds used for food in China
4000 B.C. Textiles made of hemp are used in China. Remains have been found of hemp fibers from this period and from Turkestan a century later. 1
2727 B.C. First recorded use of cannabis as medicine in Chinese pharmacopoeia. In every part of the world humankind has used cannabis for a wide variety of health problems. 2
1500 B.C. Cannabis cultivated in China for food and fiber
1500 B.C. Scythians cultivate cannabis and use it to weave fine hemp cloth. (Sumach 1975)
1200 - 800 BCE Bhang (dried cannabis leaves, seeds and stems) is mentioned in the Hindu sacred text Atharva veda (Science of Charms) as "Sacred Grass", one of the five sacred plants of India. It is used by medicinally and ritually as an offering to Shiva. 3
700 - 600 BCE The Zoroastrian Zend-Avesta, an ancient Persian religious text of several hundred volumes, and said to have been written by Zarathustra (Zoroaster), refers to bhang as Zoroaster's "good narcotic" (Vendidad or The Law Against Demons)
700 - 300 BCE Scythian tribes leave Cannabis seeds as offerings in royal tombs.
500 B.C. Scythian couple die and are buried with two small tents covering censers. Attached to one tent stick was a decorated leather pouch containing wild Cannabis seeds. This closely matches the stories told by Herodotus. The gravesite, discovered in the late 1940s, was in Pazryk, northwest of the Tien Shan Mountains in modern-day Khazakstan.
500 B.C. Hemp is introduced into Northern Europe by the Scythians. An urn containing leaves and seeds of the Cannabis plant, unearthed near Berlin, is dated to about this time.
500 - 100 BCE Hemp spreads throughout northern Europe.
430 B.C. Herodotus reports on both ritual and recreation use of Cannabis by the Scythians (Herodotus The Histories 430 B.C. trans. G. Rawlinson).
100 - 0 BCE The psychotropic properties of Cannabis are mentioned in the newly compiled herbal Pen Ts'ao Ching which is attributed to an emperor c. 2700 B.C.
0 - 100 A.D. Construction of Samartian gold and glass paste stash box for storing hashish, coriander, or salt, buried in Siberian tomb.
70 Dioscorides mentions the use of Cannabis as a Roman medicament.
170 Galen (Roman) alludes to the psychoactivity of Cannabis seed confections.
500 - 600 The Jewish Talmud mentions the euphoriant properties of Cannabis. (Abel 1980)
900 - 1000 Scholars debate the pros and cons of eating hashish. Use spreads throughout Arabia.
1090 - 1256 In Khorasan, Persia, Hasan ibn al-Sabbah, the Old Man of the Mountain, recruits followers to commit assassinations...legends develop around their supposed use of hashish. These legends are some of the earliest written tales of the discovery of the inebriating powers of Cannabis and the supposed use of Hashish. 1256 Alamut falls
Early 12th Century Hashish smoking very popular throughout the Middle East.
12th Century Cannabis is introduced in Egypt during the reign of the Ayyubid dynasty on the occasion of the flooding of Egypt by mystic devotees coming from Syria. (M.K. Hussein 1957 - Soueif 1972)
1155 - 1221 Persian legend of the Sufi master Sheik Haidar's of Khorasan's personal discovery of Cannabis and it's subsequent spread to Iraq, Bahrain, Egypt and Syria. Another of the ealiest written narratives of the use of Cannabis as an inebriant.
13th Century The oldest monograph on hashish, Zahr al-'arish fi tahrim al-hashish, was written. It has since been lost.
13th Century Ibn al-Baytar of Spain provides a description of psychaoctive Cannabis.
13th Century Arab traders bring Cannabis to the Mozambique coast of Africa.
1231 Hashish introduced to Iraq in the reign of Caliph Mustansir (Rosenthal 1971)
1271 - 1295 Journeys of Marco Polo in which he gives second-hand reports of the story of Hasan ibn al-Sabbah and his "assassins" using hashish. First time reports of Cannabis have been brought to the attention of Europe.
1378 Ottoman Emir Soudoun Scheikhouni issues one of the first edicts against the eating of hashish.
1526 Babur Nama, first emperor and founder of Mughal Empire learned of hashish in Afghanistan.
1549 Angolan slaves brought cannabis with them to the sugar plantations of northeastern Brazil. They were permitted to plant their cannabis between rows of cane, and to smoke it between harvests. 3
mid 16th Century The epic poem, Benk u Bode, by the poet Mohammed Ebn Soleiman Foruli of Baghdad, deals allegorically with a dialectical battle between wine and hashish.
17th Century Use of hashish, alcohol, and opium spreads among the population of occupied Constantinople
1606-1632 French and British cultivate Cannabis for hemp at their colonies in Port Royal (1606), Virginia (1611), and Plymouth (1632). 3
Late 17th Century Hashish becomes a major trade item between Central Asia and South Asia.
1798 Napoleon discovers that much of the Egyptian lower class habitually uses hashish (Kimmens 1977). He declares a total prohibition. Soldiers returning to France bring the tradition with them.
19th Century Hashish production expands from Russian Turkestan into Yarkand in Chinese Turkestan.
1809 Antoine Sylvestre de Sacy, a leading Arabist, reveals the etymology of the words "assassin" and "hashishin"
1840 In America, medicinal preparations with a Cannabis base are available. Hashish available in Persian pharmacies.
1840s Heydey of the Club des Hachichins in Paris. 3
1843 Le Club des Hachichins, or Hashish Eater's Club, established in Paris.
after 1850 Hashish appears in Greece.
1856 British tax ganja and charas trade in India
1870 - 1880 First reports of hashish smoking on Greek mainland
c. 1875 Cultivation for hashish introduced to Greece
1877 Kerr reports on Indian ganja and charas trade.
1890 Greek Department of Interior prohibits importance, cultivation and use of hashish.
1890 Hashish made illegal in Turkey
1893 - 1894 The India Hemp Drugs Commission Report is issued.
1893 - 1894 70,000 to 80,000 kg of hashish legally imported into India from Central Asia each year.
1906 Pure Food and Drug Act is passed, regulating the labelling of products containing Alcohol, Opiates, Cocaine, and Cannabis, among others. The law went into effect Jan 1, 1907 4 [Details]
Early 20th Century Hashish smoking very popular throughout the Middle East.
1915 - 1927 Cannabis begins to be prohibited for nonmedical use in the U.S., especially in SW states...California (1915), Texas (1919), Louisiana (1924), and New York (1927).
1920 Metaxus dictators in Greece crack down on hashish smoking.
1920s Hashish smuggled into Egypt from Greece, Syria, Lebanon, Turkey, and Central Asia
1926 Lebanese hashish production peaks after World War I until prohibited in 1926.
1928 Recrational use of Cannabis is banned in Britain.
1920s - 1930s High-quality hashish produced in Turkey near Greek border.
1930 Yarkand region of Chinese Turkestan exports 91,471 kg of hashish legally into the Northwest Frontier and Punjab regions of India
1930s Legal taxed imports of hashish continue into India from Central Asia.
1934 - 1935 Chinese government moves to end all Cannabis cultivation in Yarkand and charas traffic from Yarkand. Both licit and illicit hashish production become illegal in Chinese Turkestan.
1936 Propaganda film "Reefer Madness" made to scare American youth away from using Cannabis.
1937 Cannabis made federally illegal in the U.S. with the passage of the Marihuana Tax Act.
1938 Supply of hashish from chinese Turkestan nearly ceases.
1940s Greek hashish smoking tradition fades.
1941 Indian government considers cultivation in Kashmir to fill void of hashish from Chinese Turkestan.
1941 - 1942 Hand-rubbed charas from Nepal is choicest hashish in India during World War II.
1945 Legal hashish consumption continues in India
1945 - 1955 Hashish use in Greece flourishes again
1950s Hashish still smuggled into India from Chinese Central Asia
1950s Moroccan government tacitly allows kif cultivation in Rif Mountains.
1962 First hashish made in Morocco.
1963 Turkish police seize 2.5 tons of hashish
1965 First reports of C. afghanica use for hashish production in northern Afghanistan
1965 Mustafa comes to Ketama in Morocco to make hashish from local kif.
1966 The Moroccan government attempts to purge kif growers from Rif Mountains.
1967 "Smash", the first hashish oil appears. Red Lebanese reaches California.
Late 1960s - Early 1970s The Brotherhood popularizes Afghani hashish.
1970 - 1973 Huge fields of Cannabis cultivated for hashish production in Afghanistan. Last years that truly great afghani hashish is available
1972 The Nixon-appointed Shafer Commission urged use of cannabis be re-legalized, but their recommendation was ignored. Medical research continues. 2
Early 1970s Lebanese red and blonde hashish of very high-quality exported. The highest quality Turkish hashish from Gaziantep near Syria appears in western Europe.
Early 1970s Afghani hashish varieties introduced to North America for sinsemilla production. Westerners bring metal sieve cloths to Afghanistan. Law enforcement efforts against hashish begin in Afghanistan
1973 Nepal bans the Cannabis shops and charas (hand-rolled hash) export.
1973 Afghan government makes hashish production and sales illegal. Afghani harvest is pitifully small.
1975 FDA establishes Compassionate Use program for medical marijuana.
1976 - 1977 Quality of Lebanese hashish reaches zenith.
1978 Westerners make sieved hashish in Nepal from wild Cannabis.
Late 1970s Increasing manufacture of "modern" Afghani hashish. Cannabis varieties from Afghanistan imported into Kashmir for sieved hashish production.
1980s Morocco becomes one of, if not the largest, hashish producing and exporting nations.
1980s "Border" hashish produced in northwestern Pakistan along the Afghan border to avoid Soviet-Afghan war.
Early 1980s Quality of Lebanese hashish declines.
1983 - 1984 Small amounts of the last high-quality Turkish hashish appear.
1985 Hashish still produced by Muslims of Kashgar and Yarkland (NW China).
1986 Most private stashes of pre-war Afghani hashish in Amsterdam, Goa, and America are nearly finished.
May 13, 1986 Dronabinol is placed into Schedule II by the DEA. 5
1987 Moroccan government cracks down upon Cannabis cultivation in lower eleations of Rif Mountains.
1988 DEA administrative law Judge Francis Young finds after thorough hearings that marijuana has clearly established medical use and should be reclassified as a prescriptive drug. His recommendation is ignored.
1993 Cannabis eradication efforts resume in Morocco.
1994 Heavy fighting between rival Muslim clans continues to upset hashish trade in Afghanistan
1994 Border hashish still produced in Pakistan.
1995 Introduction of hashish-making equipment and appearance of locally produced hashish in Amsterdam coffee shops.
Oct 23, 2001 Britain's Home Secretary, David Blunkett, proposes relaxing the classification of cannabis from a class B to class C. As of June 10, 2002, this has not taken effect. [More Info]
June 2003 Canada is first country in the world to offer medical marijuana to its patients.
G
Guest
http://www.geocities.com/tasosmit2001/fossils.htm
The oldest fossil footprint
The oldest fossil footprint yet found was discovered in June 1968 by William J. Meister on an expedition to Antelope Spring, 43 miles west of Delta, Utah. He was accompanied by his wife and two daughters, and by Mr. and Mrs. Francis Shape and their two daughters. The party had already discovered several fossils of trilobites when Meister split open a two-inch-thick slab of rock with his hammer and discovered the print. The rock fell open "like a book." revealing on one side the footprint of a human with trilobites right in the footprint itself. The other half of the rock slab showed an almost perfect mold of the footprint and fossils. Amazingly the human was wearing a sandal! The sandal that seems to have crushed a living trilobite (300 to 600 million years ago) was 10 1/4 inches long and 3 1/2 inches wide; the heel is indented slightly more than the sole, as a human shoe print would be !
The oldest fossil footprint
The oldest fossil footprint yet found was discovered in June 1968 by William J. Meister on an expedition to Antelope Spring, 43 miles west of Delta, Utah. He was accompanied by his wife and two daughters, and by Mr. and Mrs. Francis Shape and their two daughters. The party had already discovered several fossils of trilobites when Meister split open a two-inch-thick slab of rock with his hammer and discovered the print. The rock fell open "like a book." revealing on one side the footprint of a human with trilobites right in the footprint itself. The other half of the rock slab showed an almost perfect mold of the footprint and fossils. Amazingly the human was wearing a sandal! The sandal that seems to have crushed a living trilobite (300 to 600 million years ago) was 10 1/4 inches long and 3 1/2 inches wide; the heel is indented slightly more than the sole, as a human shoe print would be !
T
THCV
JWP, the answer to your question is OG Kush. Why? Cuz it's the highest in the things that get you super high. Seek it out. 
Nah, for real, i agree with many on this thread. Smoke as much different stuff as you can until you find what YOU like best. To each their own with the Heezy. THC levels don't matter much, i have smoked lower THC strains that were totally wonderful highs--main thing is "self-titration", ie you will stop smoking whatever strain when you are high enough, and then you will either enjoy the high or not. High levels of THC and terps might get you higher off of one hit, but that surely isn't much of a goal? After all, most of us here like smoking enough that we aren't looking for a "1 hit a day" weed.
Put it this way: when I smoke OG, I can't smoke more than half a J without getting unnecessarily high
But with White Widow, I can smoke the whole J. At the end of either session, I am fully blazed. So from there, it's time to analyze the high itself--is it what you like? That is all that matters.
That said, many of the popular strains on ICM, both seed and clone, have GREAT highs. That's why we grow them! None of us are trying to grow weak herb. See what people like, what sounds good to you, and get that. And forget about getting numbers. The majority of the best strains have had no testing other than us hardcore stoners firing it up.
Nah, for real, i agree with many on this thread. Smoke as much different stuff as you can until you find what YOU like best. To each their own with the Heezy. THC levels don't matter much, i have smoked lower THC strains that were totally wonderful highs--main thing is "self-titration", ie you will stop smoking whatever strain when you are high enough, and then you will either enjoy the high or not. High levels of THC and terps might get you higher off of one hit, but that surely isn't much of a goal? After all, most of us here like smoking enough that we aren't looking for a "1 hit a day" weed.
Put it this way: when I smoke OG, I can't smoke more than half a J without getting unnecessarily high
But with White Widow, I can smoke the whole J. At the end of either session, I am fully blazed. So from there, it's time to analyze the high itself--is it what you like? That is all that matters.That said, many of the popular strains on ICM, both seed and clone, have GREAT highs. That's why we grow them! None of us are trying to grow weak herb. See what people like, what sounds good to you, and get that. And forget about getting numbers. The majority of the best strains have had no testing other than us hardcore stoners firing it up.
brainthor said:
You did say Cannabis, did you forget?
Am I missing something or is brainthor saying that humans and Cannabis have been around for 600 million years? I guess I did presume that you were refering to Human liver disease & itching, as well as sleep & depression by Humans, and if it has been doing it for 600 million years then I guess you believe that Cannabis plants were around 600 million years ago? Please show me any scientific proof that backs this up. It does not exist.
-SamS
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Wayzer
Active member
u can't prove him wrong skunkmn... Give evidence that completely disproves him, what are u gonna base it on? Ur saying humans or weed Couldnt have been around for more time than u think? WHY? SHOW ME PROOF!
I think what brainthor is saying is fully possible and he has not once claimed 100% fact. NOTHING is 100% fact. Whatever anybody says is gonna be debatable regarding history. He has good solid info, with back-up, and ur just screaming NO.. a Little douchy.
he is saying weed is good, if ur not getting it, and i'm almost positive u agree. as for the opinions u dont share, who the fuck cares.
I think what brainthor is saying is fully possible and he has not once claimed 100% fact. NOTHING is 100% fact. Whatever anybody says is gonna be debatable regarding history. He has good solid info, with back-up, and ur just screaming NO.. a Little douchy.
he is saying weed is good, if ur not getting it, and i'm almost positive u agree. as for the opinions u dont share, who the fuck cares.
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Well I guess 6000BC was 600 million years ago....Sam lol...
Brainthor/SproutCo...please don't attact 1 of the best breeders on IC.. Sam the Skunkman knows more than any1 on IC....geeeeez He brought the Haze Bros haze to Nev....how long ago was that....maybe 600 mil
Brainthor/SproutCo...please don't attact 1 of the best breeders on IC.. Sam the Skunkman knows more than any1 on IC....geeeeez He brought the Haze Bros haze to Nev....how long ago was that....maybe 600 mil
G
Guest
ok i do a little research...you do none...you just want to disprove what i say but you cant...you cant even give me a link to info just you and you alone know for a fact what science says is so..is not...well maybe so...maybe no...lighten up...do you hate cannabis that much much?
Sam_Skunkman said:
G
Guest
i think you need to get off of someones nutts...i never attacked anyone..im not sprotco
Americangrower said:Well I guess 6000BC was 600 million years ago....Sam lol...
Brainthor/SproutCo...please don't attact 1 of the best breeders on IC.. Sam the Skunkman knows more than any1 on IC....geeeeez He brought the Haze Bros haze to Nev....how long ago was that....maybe 600 mil
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Greens
Active member
Sam_Skunkman said:
Sam, this is something I will always disagree with you about. You are right that cannabinoids USED to be considered compounds produced by the cannabis plant that bind to CB receptors. However, today almost every scientist who studies cannabinoids now considers ALL compounds that bind to the CB receptors cannibinoids, whether they come from a plant, within our own bodies, or synthesized in a lab. Anandimide is a classical endocannbinoid and as such it IS a cannabinoid. THC is a classical phytocannabinoid and as such it is a cannabinoid. I mean, we went through this already and you even provided the evidence that proved me right (remember the old "other cannabinoid thread at OG). Remember, all phytocannabinoid means is a cannabinoid produced by a plant and all endocannabinoid means is a cannabinoid produced within an animal body.
As a side note, I really do take seriously everything you said about cannabis and cannibinoids. You were the one who got me to understand how huge of a role the terpenes play in order to get you high.
Greens
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Greens,
If brainthor meant "endocannabinoids produced by non-human life within their bodies 600 million years ago. He is saying that there is evidence of cannabinoid receptors in life at that time. He's probably right..."
Then that is what he should of said, not Cannabis, and his allusions to humans 600 million years ago, he has moved back the age of Man by hundreds of millions of years and it just ain't so.
And Greens, how many Cannabinoids are there? What is the total number?
I have no problems with the words Phytocannabinoid or Endocannabinoid, but I do find calling Anadamide a Cannabinoid confusing to say the least. Maybe I am old school, or maybe anyone that calls Anadamide a Cannabinoid is just being lazy or incomplete, it just don't sound right to me, and is confusing to say the least.
BTW, not all Canabinoids bind to the CB1 & CB2 receptors, a good example is CBD. Does that mean it is still a Cannabinoid?
-SamS
If brainthor meant "endocannabinoids produced by non-human life within their bodies 600 million years ago. He is saying that there is evidence of cannabinoid receptors in life at that time. He's probably right..."
Then that is what he should of said, not Cannabis, and his allusions to humans 600 million years ago, he has moved back the age of Man by hundreds of millions of years and it just ain't so.
And Greens, how many Cannabinoids are there? What is the total number?
I have no problems with the words Phytocannabinoid or Endocannabinoid, but I do find calling Anadamide a Cannabinoid confusing to say the least. Maybe I am old school, or maybe anyone that calls Anadamide a Cannabinoid is just being lazy or incomplete, it just don't sound right to me, and is confusing to say the least.
BTW, not all Canabinoids bind to the CB1 & CB2 receptors, a good example is CBD. Does that mean it is still a Cannabinoid?
-SamS
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Greens
Active member
You know I was just thinking that this is just a matter of semantics. I mean, it's just a matter of whether you want to use a broader definition of the word "cannabinoid" or not. We probably don't know the totaly number of cannabinoids yet (and obviously not if you include non-classical synthetic cannabinoids).
Greens
Greens
G
Guest
i guess 21 offended you..shall i edit it...nobodys perfect
Sam_Skunkman said:
G
Guest
more on the cannabinoids cause its so darn interesting and more controversial than i would have thought
It is now well established that the psychoactive effects of Cannabis sativa are primarily mediated through neuronal CB1 receptors, while its therapeutic immune properties are primarily mediated through CB2 receptors. Two endocannabinoids, arachidonoylethanolamide and 2-arachidonoylglycerol, have been identified, their action on CB1 and CB2 thoroughly characterized, and their production and inactivation elucidated. However, many significant exceptions to these rules exist. Here we review the evidence suggesting that cannabinoids can modulate synaptic transmission, the cardiovascular system, and the immune system through receptors distinct from CB1 and CB2, and that an additional “independent” endocannabinoid signaling system that involves palmitoylethanolamide may exist.
Introduction
Cannabis sativa, also known as marijuana or hashish depending on the particular preparation, is both a widespread illegal drug of abuse and a well-recognized medicinal plant.1,2 A current challenge in pharmacology is to increase our understanding of the molecular mechanisms underlying the abuse property of C sativa in order to develop means to prevent it. Another challenge is to isolate the bioactive components that impart the medicinal properties ascribed to this plant with the goal of developing novel, cannabinoid-based therapeutics devoid of adverse effects. After approximately 40 years of research, we have a much clearer understanding of the pharmacology and molecular mechanisms mediating the bioactivity of plant-derived cannabinoid compounds, the phytocannabinoids, and are getting much closer to overcoming these 2 challenges.
C sativa contains ~60 phytocannabinoids, a handful of which are bioactive as defined by their ability to specifically interact with membrane-associated receptors, the cannabinoid receptors. The best-known phytocannabinoid is ∆9-tetrahydrocannabinol (THC),3 which is thought to mediate most—if not all—of the psychotropic and addictive properties of C sativa.4 Recent evidence suggest that some of the antiinflammatory properties of C sativa may be accounted for by cannabinol (CBN) and cannabidiol (CBD), 2 nonpsychotropic phytocannabinoids that constitute promising lead compounds to develop cannabinoid-based antiinflammatory medicines.5,6 Thus, while some might focus on THC to study the psychotropic and addictive properties of C sativa, others might focus on CBN and CBD as a means to develop cannabinoid-based antiinflammatory therapeutics devoid of adverse effects. Here we will review our current understanding of the cannabinoid receptors that mediate the effects of cannabinoids and provide examples of the biological functions regulated by them, with a special emphasis on those receptors that have been pharmacologically characterized and yet still remain to be cloned. We will also review our current understanding of the endogenous cannabinoids, the endocannabinoids, with a special emphasis on palmitoylethanolamide (PEA), whose production and inactivation can occur independently of other endocannabinoids, and whose biological effects are mediated by interactions with one of the novel cannabinoid receptors.
Cannabinoids Activate at Least 5 Distinct Cannabinoid Receptors
Two cannabinoid receptors, CB1 and CB2, have been identified by molecular cloning and are unambiguously established as mediators of the biological effects induced by cannabinoids, either plant derived, synthetic, or endogenously produced. CB1 and CB2 are 7 transmembrane Gi/o-coupled receptors that share 44% protein identity and display different pharmacological profiles and patterns of expression,7,8 a dichotomy that provides a unique opportunity to develop pharmaceutical approaches. Studies performed with CB1−/− and/or CB2−/− mice identified additional cannabinoid receptors, 3 of which will be discussed below.
CB1 Receptors
The vast majority of CB1 receptors are expressed in the central nervous system (CNS), and their distribution in this tissue has been documented in detail using highly specific antibodies and CB1−/− tissue controls. The current picture depicts abundant presynaptic expression in the adult mammalian brain.9 In some cases, these receptors are also present on the dendrites and soma of neurons,10 although at lower levels and frequency than their presynaptic counterparts. CB1 receptors are also expressed at low levels by various astrocytes, oligodendrocytes, and neural stem cells.11-13 To the best of our knowledge, expression of CB1 receptors in situ by ependymal cells and/or microglia has not been reported.
CB1 receptors couple to Gi/o proteins and, under specific conditions, also to Gs proteins (only when other Gi/o protein-coupled receptors are concomitantly activated).14,15 By coupling to Gi/o proteins, CB1 receptors regulate the activity of many plasma membrane proteins and signal transduction pathways, including ion channels, enzymes producing cyclic nucleotide second messengers, and various kinases. Thus, depending on the coupling and cell type expressing CB1 receptors, cannabinoids may regulate distinct cell functions. For example, activation of presynaptic CB1 receptors inhibits N-type calcium channels, thus reducing synaptic transmission.9 It is likely that THC induces most—if not all—of its acute cognitive and intoxicating effects through this molecular mechanism.16 Whether THC produces its effect by partially activating CB1 receptors or antagonizing the action of endocannabinoids on this receptor remains an open question.17,18 Activation of CB1 receptors expressed on the somata of neurons increases Erk activity and induces brain-derived neurotrophic factor (BDNF) expression.10 It is likely that the neuroprotective properties of cannabinoids are in part mediated through this mechanism. Recent evidence shows that CB1 receptor may also control the fate of neural stem cells, the outgrowth of neurites and the formation of functional synapses, emphasizing the importance of this receptor in the remodeling of neuronal networks.13,19-21 Note that blood-derived leukocytes also express CB1 receptors,22 suggesting that under neuropathological conditions, whereby the blood brain barrier is disrupted, cannabinoids accumulating in the CNS likely activate CB1 receptors expressed by invading leukocytes and thereby modulate the development of neuroinflammation.23-25
CB2 Receptors
Under nonpathological conditions, CB2 receptors are primarily expressed by leukocytes (with a rank order of B cells > natural killer [NK] cells >> monocytes/macrophages > neutrophils > CD8+ T cells > CD4+ T cells). Furthermore, experiments performed with CB2−/− mice show that cannabinoids engaging these receptors lead to changes in immune responses, particularly at the level of macrophage-induced helper T-cell activation.8,22,26 CBN is more efficacious at CB2 receptors than THC,27 making this phytocannabinoid more likely to account for the antiinflammatory properties of C sativa. For example, activation of CB2 receptors inhibits the ability of macrophages to process antigens and prime helper T cells26,28-31 and at high concentrations may induce immune cell apoptosis.32
While many laboratories have reported the absence of CB2 receptor expression in healthy brain,8,22,33-36 a new study has found that neurons located in specific brain structures, such as the brain stem, express detectable levels of CB2 mRNA and functional receptors, the activation of which is thought to regulate emesis.37 Furthermore, while resting microglia present in healthy CNS tissue express few—if any—CB2 receptors, activated microglial cells, such as those found in mouse models of multiple sclerosis and Alzheimer’s disease, express significant levels of CB2 receptors.38,39 This result is not surprising since pathological conditions are known to induce CB2 receptor expression in leukocytes.36 Microglial cells in culture, which by default are considered chronically activated, also express CB2 receptors, particularly at the leading edges of lamellipodia, protrusions involved in cell migration.40 Accordingly, application of CB2 agonists induces cell migration, a response that can be extended to other CB2-expressing cells.41-43 Furthermore, several laboratories have shown that CB2 agonists reduce the release of cytotoxins by immune cells and increase their proliferation rate.44-47 Taken together, these studies suggest that the ability of CB2-selective compounds to reduce inflammation might be caused by an increase in proliferation and recruitment of immune cells, in particular a population of immune cells that do not release detrimental mediators and thus could be involved in the immune-mediated repair of damaged tissue. Again, blood-derived leukocytes expressing CB2 receptors and invading the CNS via a disrupted blood brain barrier are likely to be activated by cannabinoids accumulating in the CNS and to modulate the development of neuroinflammation. Whether astrocytes and endothelial cells express CB2 receptors remains controversial as control experiments using CB2−/− tissue have yet to be performed.
Similar to CB1 receptors, CB2 receptors also couple to Gi/o proteins and regulate the activity of signal transduction pathways, including enzymes that produce cyclic nucleotide second messengers and various kinases. Accordingly, increased Erk activity via activation of CB2 receptors induces immune cell migration and changes in gene expression.40,48 When expressed in AtT-20 cells, CB2 receptors do not modulate ion conductances, making this function unique to CB1 receptors.27 This result poses an intriguing question: considering that some neurons express CB2 receptors, does activation of this receptor affect the firing rate of these neurons and, if so, through what signal transduction pathway?
Two Endocannabinoids
The existence of cannabinoid receptors and the biological effects induced by cannabinoids suggests the existence of endocannabinoids that normally engage these receptors. Arachidonoylethanolamide (AEA), also known as anandamide, was identified in 1992 by Devane and colleagues and shown to bind with high affinity to CB1 receptors.49 Since then, AEA has been extensively studied and shown to fulfill the 3 criteria necessary to be considered a bona fide endocannabinoid: (1) activity-dependent production, (2) functional activation of cannabinoid receptors, and (3) biological inactivation.
Activity-dependent production of AEA was demonstrated in neurons in primary culture and in the brain of freely moving rats using microdialysis.50-52 The molecular mechanism underlying AEA biosynthesis and hydrolysis is beginning to be understood. Depending on the cell type, stimuli that increase intracellular concentrations of calcium increase AEA production.50,53 Calcium-dependent increases in AEA production are likely mediated through calcium-dependent increases in the activity of acyltransferase, the enzyme that generates the AEA precursor N-arachidonylphosphatidylethanolamide (NAPE).54,55 A recently cloned NAPE-phospholipase D may be responsible for cleaving this precursor.56 Thus, unlike classical transmitter substances, AEA is produced upon demand by enzymatic cleavage of membrane lipid precursors and immediately extruded from cells without an intermediate step of vesicle storage, a feature reminiscent of other lipid-derived mediators.57 AEA production is not restricted to neurons since many different cell types, including astrocytes and microglial cells, also produce this ligand.40,58-62
AEA activates the signal transduction pathways coupled to CB1 receptors, although it has a low intrinsic efficacy.63 Injection of AEA into rodents mimics most of the effects produced by THC,64 although inactivation of its degradation is often necessary to see biological effects.65 AEA also binds CB2 receptors, acting as a partial agonist, or antagonist,66,67 effects that might have some relevance in modulating inflammation.
Strong genetic and pharmacological evidence has demonstrated that fatty acid amide hydrolase (FAAH) inactivates AEA.65,68 Of interest, other enzymes may also metabolize AEA, including cyclooxygenases and lipooxygenases.69,70 Their respective involvement in AEA inactivation in intact cells, especially when FAAH is also expressed, is starting to be unraveled.71,72
In 1995, the laboratories of Raphael Mechoulam and Keizo Waku simultaneously reported a second endogenous ligand, 2-arachidonylglycerol (2-AG).73,74 Neuronal activity enhances 2-AG synthesis, its levels reaching 100 times that of AEA.75 While classic studies have shown that 2-AG is produced through the phospholipase C (PLC)/diacylglycerol lipase (DGL) pathway,76,77 more recent genetic studies show that PLCβ1 and PLCβ4 mediate 2-AG biosynthesis in pyramidal and Purkinje neurons, respectively,78,79 and that there exist 2 subtypes, α and β, of DGL directly controlling its biosynthesis.80
2-AG activates CB1 and CB2 receptors with distinct pharmacological profiles, is carried into cells by a “yet-to-be” cloned transporter, and is inactivated by monoacylglycerol lipase (MGL).81-84 When MGL protein is fully knocked down by RNA interference (RNAi), 50% of the 2-AG hydrolyzing activity remains in cell homogenates, indicating that additional enzymes may hydrolyze this lipid.85 Prime candidates are FAAH and the cyclooxygenases.86,87
In summary and as a first approximation, psychoactive effects of cannabis are primarily mediated by neuronal CB1 receptors, while immune effects are primarily mediated by CB2 receptors. Two endocannabinoids have been identified, their action on either CB1 or CB2 is thoroughly characterized, and their production and inactivation elucidated; however, many significant exceptions to these rules exist. Indeed, convincing evidence now suggests that specific cannabinoid effects on synaptic transmission, the cardiovascular system, and immune system are mediated by cannabinoid receptors distinct from CB1 and CB2, and that additional “independent” endocannabinoids exist. Below we will briefly review this evidence.
Non-CB1/CB2 Receptors on Neurons
Three sets of experiments, each using the approach of applying cannabinoids to CB1−/− mice, support the existence of non-CB1/CB2 receptors regulating synaptic transmission. The first were experiments examining GTPγS binding in brain membranes prepared from CB1−/− mice. Breivogel and colleagues found that AEA and the aminoalkylindole WIN55,212-2 stimulated GTPγS binding in brain homogenates prepared from these mice.88,89 The regional distribution of GTPγS binding only partially overlapped those of CB1 or CB2 receptors, emphasizing that these novel receptors likely have a distinct physiological role. Furthermore, this novel receptor was stimulated by WIN55,212-2 and anandamide but not by CP55,940, HU210, or THC and was only weakly antagonized by SR141716A, emphasizing a pharmacology divergent from CB1 and CB2.
The second set of experiments supporting the existence of non-CB1/CB2 cannabinoid receptor(s) examined glutamatergic transmission in CA1 of mouse hippocampus.90,91 Hájos and colleagues found that WIN55,212-2 and CP55,940 inhibited excitatory transmission with equal efficacy in wild-type and CB1−/− mice. Of interest, a recent report showed that while CD1 mice had this response, the C57BL-6 strain did not.92 This inhibitory effect of WIN55212-2 and CP55940 was abolished by SR141716 and capsazepine but was unaffected by the SR141716 analog, AM251.90 As WIN55,212-2 and CP55,940 do not interact with TRPV1 channels, it is unlikely that TRPV1 mediates this response. Additional evidence suggested that these novel receptors are involved in endocannabinoid-mediated short-term plasticity. Specifically, Rouach and Nicoll93 found that activation of group I metabotropic glutamate receptors in CB1−/− mice causes short-term depression of excitatory transmission in the hippocampal CA1 region that is blocked by SR141716. A pharmacologically similar receptor is also present on amygdala projection neurons, and this novel receptor likely plays a role in anxiety, as shown by antagonist experiments in rodents.94
The third set of experiments examined the analgesic efficacy of THC in spinal cord. Welch and coworkers found that the rank order potency of SR141716A in blocking analgesia produced by THC, anandamide, and CP55,490 differed from that predicted by a CB1-mediated response.95,96 In addition, there were also differences in the synergy between morphine and THC compared with morphine and AEA or CP55,940, suggesting the involvement of a novel receptor.
Non-CB1/CB2 Receptors in the Vasculature
Very strong evidence for non-CB1/CB2 cannabinoid receptors comes from a continuing series of investigations performed by several laboratories studying the effects of cannabinoids on the vasculature.97 Essentially the findings are that certain cannabinoids cause vasodilation and hypotension in the absence of CB1, CB2, or TRPV1 receptor activation. The best-characterized response is in mesenteric vessels,98 in which AEA and its analog methanandamide cause vasodilation, while synthetic cannabinoids and THC do not. This response is sensitive to high concentrations (>1 µM) of SR141716A. Similar to the inhibitory effect on hippocampal glutamatergic transmission described above, the SR141716A analog AM251 does not antagonize this novel receptor. The response is, however, sensitive to pertussis toxin, implicating Gi or Go proteins in the signaling pathway. An important pharmacological tool for non-CB1/CB2 cannabinoid receptors that emerged from these studies is the cannabidiol analog, abnormal cannabidiol (abn-CBD).98 Abn-CBD functions as an agonist at some of these novel cannabinoid receptors, is inactive at CB1 and CB2 receptors, and is antagonized by both cannabidiol and O-1918, a synthetic cannabidiol analog.99 Several lines of evidence suggest that endothelial cells express this novel cannabinoid receptor, and its activation leads to the release of nitric oxide, culminating in the opening of potassium channels on vascular smooth muscle and leading to relaxation and vasodilation.100 Although there are strong pharmacological parallels between the vascular and hippocampal novel receptors, there are some notable differences. For example, the vascular receptor is insensitive to potent synthetic cannabinoids. It is possible that such differences arise from distinct receptor entities, the specific cellular context in which the receptor is expressed or receptor dimerization.
Non-CB1/CB2 Receptors on Immune Cells
Immune cells express both CB1 and CB2 receptors, the levels of which vary depending on the activation state of immune cells. For example, while mature B cells express high levels of CB1 and CB2 receptors, naïve T cells express very low levels of either receptor.101 Strong evidence suggests that cannabinoids interact with CB1 and CB2 receptors expressed by immune cells, increasing their proliferation rate and survival, while inhibiting the production of various immune mediators such as cytokines.102,103 As such, many of the therapeutic, anti-inflammatory properties attributed to C sativa intake likely occur through this mechanism. Yet recent convincing evidence shows that immune cells likely express at least one additional cannabinoid receptor. These experiments were performed with palmitoylethanolamide (PEA, an analog of anandamide that contains a 16:0 fatty acid moiety instead of 20:4 for AEA), which has received considerable attention because of its antiinflammatory properties.104 Piomelli and colleagues, and, simultaneously, Rice and colleagues, found that PEA reduces the pain associated with an inflammatory response.58,105 This analgesic effect of PEA likely involves a novel cannabinoid receptor because SR144528, a well-characterized CB2 antagonist, blocked the analgesia, yet PEA does not bind to CB2 receptors.66 Two hypotheses stem from these results: (1) PEA might interact with a novel cannabinoid receptor that is antagonized by SR144528 (thus this antagonist is not specific for CB2 receptors), or (2) PEA might stimulate a novel cannabinoid receptor that couples to phospholipases C and diacylglycerol lipase, increases 2-AG production, and thus indirectly activates CB2 receptors. Currently, the signal transduction pathway(s) coupled to the novel PEA-sensitive receptor is unknown.
PEA: An Independent Endocannabinoid?
Results showing that PEA interacts with a distinct non-CB1/CB2 receptor suggest that this lipid might constitute a unique “parallel” endocannabinoid signaling system. Providing support to this concept is the evidence that PEA production and inactivation can occur independently of AEA and 2-AG production and inactivation. Specifically, in rodent cortical neurons, general activity-dependent production of AEA, 2-AG, and PEA occurs concomitantly.50,106,107 Yet, subsequent studies showed that 2-AG production can be increased independently when N-methyl-D-aspartate (NMDA) receptors are activated, while increased AEA and PEA production requires addition of carbachol.108 A more detailed pharmacological study showed that activation of nicotinic receptors increases AEA production, while activation of muscarinic receptors increases PEA production. Thus, although biosynthesis of all endocannabinoids in this model system is contingent on NMDA-receptor occupation, increased AEA production requires the co-activation of α7 nicotinic receptors, while increased PEA production requires the co-activation of muscarinic receptors. This finding suggests that glutamate and acetylcholine may elicit the biosynthesis of different endocannabinoids depending on the complement of cholinergic receptors expressed in their target neurons. Additional evidence for independent production of AEA, 2-AG, and PEA comes from experiments performed on mouse astrocytes in culture. In this model, the calcium ionophore ionomycin and the peptide endothelin-1 increase the production of both AEA and 2-AG, while PEA levels remain unchanged.109,110 The notion that PEA might be independently produced also holds true in vivo.111 For example, in the case of focal cerebral ischemia, PEA levels in ischemic cerebral cortex increase ~25-fold compared with sham-operated animals, while AEA levels increase by barely 3-fold and 2-AG levels remain unchanged.
Novel evidence shows that PEA inactivation can also occur independently from that of AEA and 2-AG. The laboratory of Natsuo Ueda discovered the existence of a unique enzyme capable of hydrolyzing PEA to much greater extent than AEA and 2-AG. The original observation was obtained with homogenates prepared from human megakaryoblastic cells (CMK), in which AEA hydrolysis occurred with low activity and a strikingly different pH profile from that of FAAH.112 Specifically, while FAAH is known to maximally hydrolyze AEA at pH 9 (with this activity dropping by 70% at pH 5), CMK cells were shown to maximally hydrolyze AEA at pH 5 (with this activity dropping by 95% at pH 9). Using an elegant 4-step purification approach, Ueda and colleagues were able to purify this novel enzymatic activity by 760-fold, obtain partial protein sequence, and clone a cDNA encoding this protein, which was named N-acylethanolamine-hydrolyzing acid amidase (NAAA).113 When assessing its substrate specificity, it became clear that this enzyme preferred PEA over AEA (having hydrolytic activities toward these substrates of 8 and 0.25 nmol/min/mg, respectively). Besides a distinct pH profile and substrate specificity, NAAA has additionally very interesting properties. It is highly expressed in spleen and thymus, as well as in macrophages homing to the lungs and small intestine, highlighting its potential importance in regulating PEA signaling in the context of immunobiology. Here, it should be emphasized that NAAA expression and activity are quite low in healthy brain.113
The laboratory of Didier Lambert developed a competitive inhibitor of NAAA, N-cyclohexanecarbonylpentadecylamine, which has an IC50 of 5 µM and is inactive against FAAH at 100 µM.114 When considering that methyl arachidonoyl fluorophosphonate (MAFP) and URB597 inhibit FAAH with nanomolar IC50s and are both inactive against NAAA at a concentration of 1 µM, experiments designed to use these compounds in combination may be useful to distinguish the biological importance of either PEA or AEA hydrolysis in various biological responses.114,115
This series of studies raises many fascinating questions: for example, “What is the subcellular location of NAAA and does it differ from FAAH?” The pH profile of NAAA is quite intriguing. With maximal NAAA activity occurring at pH 5 and only 10% of this activity remaining at pH 7 (ie, the cytosolic pH), one wonders if NAAA might be active only in lysosomes. Accordingly, NAAA-GFP (green fluorescent protein) fusion protein localized to lysosome-like vesicles.113 This result is quite interesting when considering that FAAH is also abundant in intracellular organelles such as mitochondria and the smooth endoplasmic reticulum.116 Clearly, elucidating the exact biological role of NAAA will be facilitated by genetic studies similar to those performed on FAAH. Finally, while AEA and 2-AG hydrolysis give rise to new bioactive lipids (ie arachidonic acid and eicosanoids), PEA hydrolysis gives rise to 2 relatively inactive products, palmitic acid and ethanolamine, suggesting that the role of NAAA is to truly stop biological responses initiated by increases in PEA production.
Is GPR55 the Cannabinoid Receptor Engaged by PEA?
GPR55 was first identified as an orphan G protein coupled receptor (GPCR) enriched in brain.117 Its gene is located on chromosome 2 (location: 2q37) in mice and chromosome 6 in humans, and its open reading frame encodes a relatively short 319 amino acid protein. Using Northern blot analysis of human tissues, GPR55 mRNA was found in caudate and putamen, but not in frontal cortex, hippocampus, thalamus, pons, cerebellum, or liver.117 Northern blot analysis of rat tissues showed GPR55 mRNA in spleen, fetal tissues, and intestine. Further in situ hybridization studies found GPR55 mRNA in rat hippocampus, thalamus, and midbrain.117 The difference between the human and rat CNS studies may represent sensitivity differences between the 2 specific techniques, or a variation between species, and invites further careful study. A more thorough distribution of human GPR55 mRNA has been reported in the patent literature. A first patent reported the following relative abundance: adipose > testis > myometrium > adenoid = tonsil > spleen > ilium > brain = stomach.118 Low levels were found in other tissues. Synthesis of the above results emphasizes that GPR55 is highly expressed in tissues known to respond to cannabinoids.
A very recent second patent application argued that GPR55 might constitute an additional cannabinoid receptor subtype.119 The main findings are as follows: human GPR55 amplified from genomic DNA contains an 11 amino acid substitution in distal intracellular loop 2 and the fourth transmembrane domain not present in the originally reported GPR55 sequence. This variant was termed GPR55A and corresponds to the Human Genome Project sequence. Phylogenetically, GPR55 is closest in sequence to the platelet activating factor (PAF) purinergic P2Y9 and 2 orphan receptors GPR35 and GPR92. It has reasonable homology to several other very interesting GPCR, including P2Y5 and CCR4. It only shares 13.5% and 14.4% homology with CB1 and CB2, respectively. When expressed in HEK293 cells, GPR55A bound CP55,940 and SR141716A, but not WIN55,212-2. Signal transduction was examined using GTPγS binding. A wide range of cannabinoid compounds stimulated GTPγS binding, including THC, anandamide, 2-AG, virodhamine, and CP55,940, all with EC50 values less than 20 nM. Most remarkably, PEA also stimulated GTPγS binding with even lower nM potency. This latter result suggests the exciting possibility that GPR55 may mediate the antiinflammatory effects of PEA discussed above. Pretreatment of GPR55A expressing HEK293 membranes with pertussis toxin or cholera toxin did not alter CP55,940 stimulation of GTPγS binding, indicating that, in contrast to CB1 and CB2 receptors, GPR55A does not activate Gi, Go, or Gs proteins, at least in HEK293 cells. Thus, GPR55(A) represents a new subtype of cannabinoid receptor with ligand binding and signaling profiles distinct from those of CB1 and CB2.
Conclusion
The results discussed above clearly argue for the existence of multiple cannabinoid receptors, specifically the cloned CB1 and CB2 receptors, and at least 3 non-CB1/CB2 cannabinoid receptors. Owing to their expression profile and coupling mechanism, each receptor likely mediates distinct effects of phytocannabinoids and endocannabinoids. In addition, strong evidence implicates PEA as an inflammatory modulator acting via a non-CB1/CB2 cannabinoid receptor. While recent data suggest that this latter receptor might be GPR55, many key experiments remain to be done, such as determining the precise pharmacology of this receptor, its coupling capabilities and expression pattern. The existence of different enzymatic routes for the formation of AEA, 2-AG, and PEA suggests that these endocannabinoids may operate independently from each other.
While the place that cannabinoid receptors occupy in the field of pharmacology research is still evolving, strong evidence implicates their ability to regulate neuronal, vascular, and immune functions. An understanding of the expression, function, and regulation of these receptors, the molecular mechanism involved in the production and inactivation of their endogenous ligands, and how phytocannabinoids interfere with this signaling system is clearly important if we are rationally and comprehensively to assess the function of the cannabinoid signaling system in human health and disease.
Acknowledgements
This work was supported by the National Institute on Drug Abuse.
References
1. Watson SJ, Benson JA, Joy JE. Marijuana and medicine: assessing the science base. Arch Gen Psychiatry. 2000;57:547-552.
PubMed DOI: 10.1001/archpsyc.57.6.547
2. Iversen LL. The Science of Marijuana. Oxford, UK: Oxford University Press; 2000.
3. Gaoni Y, Mechoulam R. Isolation, structure and partial synthesis of an active constituent of hashish. J Am Chem Soc. 1964;86:1646-1647.
DOI: 10.1021/ja01062a046
4. Hall W, Solowij N. Adverse effects of cannabis. Lancet. 1998;352:1611-1616.
PubMed DOI: 10.1016/S0140-6736(98)05021-1
5. Malfait AM, Gallily R, Sumariwalla PF, et al. The nonpsychoactive cannabis constituent cannabidiol is an oral anti-arthritic therapeutic in murine collagen-induced arthritis. Proc Natl Acad Sci USA. 2000;97:9561-9566.
PubMed DOI: 10.1073/pnas.160105897
6. Herring AC, Kaminski NE. Cannabinol-mediated inhibition of nuclear factor-κB, cAMP response element-binding protein, and interleukin-2 secretion by activated thymocytes. J Pharmacol Exp Ther. 1999;291:1156-1163.
PubMed
7. Matsuda LA, Lolait SJ, Brownstein MJ, Young AC, Bonner TI. Structure of a cannabinoid receptor and functional expression of the cloned cDNA. Nature. 1990;346:561-564.
PubMed DOI: 10.1038/346561a0
8. Munro S, Thomas KL, Abu-Shaar M. Molecular characterization of a peripheral receptor for cannabinoids. Nature. 1993;365:61-65.
PubMed DOI: 10.1038/365061a0
9. Freund TF, Katona I, Piomelli D. Role of endogenous cannabinoids in synaptic signaling. Physiol Rev. 2003;83:1017-1066.
PubMed
10. Marsicano G, Goodenough S, Monory K, et al. CB1 cannabinoid receptors and on-demand defense against excitotoxicity. Science. 2003;302:84-88.
PubMed DOI: 10.1126/science.1088208
11. Rodríguez JJ, Mackie K, Pickel VM. Ultrastructural localization of the CB1 cannabinoid receptor in µ-opioid receptor patches of the rat caudate putamen nucleus. J Neurosci. 2001;21:823-833.
PubMed
12. Molina-Holgado E, Vela JM, Arévalo-Martin A, et al. Cannabinoids promote oligodendrocyte progenitor survival: involvement of cannabinoid receptor and phosphatidyllinositol-3 kinase/Akt signaling. J Neurosci. 2002;22:9742-9753.
PubMed
13. Aguado T, Monory K, Palazuelos J, et al. The endocannabinoid system drives neural progenitor proliferation. FASEB J. 2005;19:1704-1706.
PubMed
14. Felder CC, Veluz JS, Williams HL, Briley EM, Matsuda LA. Cannabinoid agonists stimulate both receptor- and non-receptor-mediated signal transduction pathways in cells transfected with and expressing the cannabinoid receptor clones. Mol Pharmacol. 1992;42:838-845.
PubMed
15. Glass M, Felder CC. Concurrent stimulation of cannabinoid CB1 and dopamine D2 receptors augments cAMP accumulation in striatal neurons: evidence for a Gs linkage to the CB1 receptor. J Neurosci. 1997;17:5327-5333.
PubMed
16. Huestis MA, Gorelick DA, Heishman SJ, et al. Blockade of effects of smoked marijuana by the CBl-selective cannabinoid receptor antagonist SR141716. Arch Gen Psychiatry. 2001;58:322-328.
PubMed DOI: 10.1001/archpsyc.58.4.322
17. Straiker A, Mackie K. Depolarization-induced suppression of excitation in murine autaptic hippocampal neurones. J Physiol. 2005;569:501-517.
PubMed DOI: 10.1113/jphysiol.2005.091918
18. Kelley BG, Thayer SA. Delta 9-tetrahydrocannabinol antagonizes endocannabinoid modulation of synaptic transmission between hippocampal neurons in culture. Neuropharmacology. 2004;46:709-715.
PubMed DOI: 10.1016/j.neuropharm.2003.11.005
19. Jordan JD, He JC, Eungdamrong NJ, et al. Cannabinoid receptor-induced neurite outgrowth is mediated by Rap1 activation through G(alpha)o/i-triggered proteasomal degradation of Rap1GAPII. J Biol Chem. 2005;280:11413-11421.
PubMed DOI: 10.1074/jbc.M411521200
20. Kim D, Thayer SA. Cannabinoids inhibit the formation of new synapses between hippocampal neurons in culture. J Neurosci. 2001;21:RC146.
PubMed
21. Jin K, Xie L, Kim SH, et al. Defective adult neurogenesis in CB1 cannabinoid receptor knockout mice. Mol Pharmacol. 2004;66:204-208.
PubMed DOI: 10.1124/mol.66.2.204
22. Galiègue S, Mary S, Marchand J, et al. Expression of central and peripheral cannabinoid receptors in human immune tissues and leukocyte subpopulations. Eur J Biochem. 1995;232:54-61.
PubMed DOI: 10.1111/j.1432-1033.1995.tb20780.x
23. Patrini G, Sacerdote P, Fuzio D, Manfredi B, Parolaro D. Regulation of immune functions in rat splenocytes after acute and chronic in vivo treatment with CP-55,940, a synthetic cannabinoid compound. J Neuroimmunol. 1997;80:143-148.
PubMed DOI: 10.1016/S0165-5728(97)00149-5
24. Richardson JD, Kilo S, Hargreaves KM. Cannabinoids reduce hyperalgesia and inflammation via interaction with peripheral CB1 receptors. Pain. 1998;75:111-119.
PubMed DOI: 10.1016/S0304-3959(97)00213-3
25. Massi P, Fuzio D, Viganò D, Sacerdote P, Parolaro D. Relative involvement of cannabinoid CB1 and CB2 receptors in the ∆9-tetrahydrocannabinol-induced inhibition of natural killer activity. Eur J Pharmacol. 2000;387:343-347.
PubMed DOI: 10.1016/S0014-2999(99)00860-2
26. Buckley NE, McCoy KL, Mezey E, et al. Immunomodulation by cannabinoids is absent in mice deficient for the cannabinoid CB(2) receptor. Eur J Pharmacol. 2000;396:141-149.
PubMed DOI: 10.1016/S0014-2999(00)00211-9
27. Felder CC, Joyce KE, Briley EM, et al. Comparison of the pharmacology and signal transduction of the human cannabinoid CB1 and CB2 receptors. Mol Pharmacol. 1995;48:443-450.
PubMed
28. Hanus L, Breuer A, Tchilibon S, et al. HU-308: a specific agonist for CB2, a peripheral cannabinoid receptor. Proc Natl Acad Sci USA. 1999;96:14228-14233.
PubMed DOI: 10.1073/pnas.96.25.14228
29. Conti S, Costa B, Colleoni M, Parolaro D, Giagnoni G. Antiinflammatory action of endocannabinoid palmitoylethanolamide and the synthetic cannabinoid nabilone in a model of acute inflammation in the rat. Br J Pharmacol. 2002;135:181-187.
PubMed
30. McCoy KL, Gainey D, Cabral GA. ∆9-tetrahydrocannabinol modulates antigen processing by macrophages. J Pharmacol Exp Ther. 1995;273:1216-1223.
PubMed
31. McCoy KL, Matveyeva M, Carlisle SJ, Cabral GA. Cannabinoid inhibition of the processing of intact lysozyme by macrophages: evidence for CB2 receptor participation. J Pharmacol Exp Ther. 1999;289:1620-1625.
PubMed
32. McKallip RJ, Lombard C, Martin BR, Nagarkatti M, Nagarkatti PS. Delta(9)-tetrahydrocannabinol-induced apoptosis in the thymus and spleen as a mechanism of immunosuppression in vitro and in vivo. J Pharmacol Exp Ther. 2002;302:451-465.
PubMed DOI: 10.1124/jpet.102.033506
33. Derocq J-M, Ségui M, Marchand J, Le Fur G, Casellas P. Cannabinoids enhance human B-cell growth at low nanomolar concentrations. FEBS Lett. 1995;369:177-182.
PubMed DOI: 10.1016/0014-5793(95)00746-V
34. Schatz AR, Lee M, Condie RB, Pulaski JT, Kaminski NE. Cannabinoid receptors CB1 and CB2: a characterization of expression and adenylate cyclase modulation within the immune system. Toxicol Appl Pharmacol. 1997;142:278-287.
PubMed DOI: 10.1006/taap.1996.8034
35. Sugiura T, Kondo S, Kishimoto S, et al. Evidence that 2-arachidonylglycerol but not N-palmitpylethanolamine or anandamide is the physiological ligand for the cannabinoid CB2 receptor: comparison of the agonistic activities of various cannabinoid receptor ligands in HL-60 cells. J Biol Chem. 2000;275:605-612.
PubMed DOI: 10.1074/jbc.275.1.605
36. Carlisle SJ, Marciano-Cabral F, Staab A, Ludwick C, Cabral GA. Differential expression of the CB2 cannabinoid receptor by rodent macrophages and macrophage-like cells in relation to cell activation. Int Immunopharmacol. 2002;2:69-82.
PubMed DOI: 10.1016/S1567-5769(01)00147-3
37. Van Sickle MD, Duncan M, Kingsley PJ, et al. Identification and functional characterization of brainstem cannabinoid CB2 receptors. Science. 2005;310:329-332.
PubMed DOI: 10.1126/science.1115740
38. Maresz K, Carrier EJ, Ponomarev ED, Hillard CJ, Dittel BN. Modulation of the cannabinoid CB2 receptor in microglial cells in response to inflammatory stimuli. J Neurochem. 2005;95:437-445.
PubMed DOI: 10.1111/j.1471-4159.2005.03380.x
39. Benito C, Núnez E, Tolón RM, et al. Cannabinoid CB2 receptors and fatty acid amide hydrolase are selectively overexpressed in neuritic plaques-associated glia in Alzheimer's disease brains. J Neurosci. 2003;23:11136-11141.
PubMed
40. Walter L, Franklin A, Witting A, et al. Non-psychotropic cannabinoid receptors regulate microglial cell migration. J Neurosci. 2003;23:1398-1405.
PubMed
41. Kishimoto S, Gokoh M, Oka S, et al. 2-Arachidonoylglycerol induces the migration of HL-60 cells differentiated into macrophage-like cells and human peripheral blood monocytes through the cannabinoid CB2 receptor-dependent mechanism. J Biol Chem. 2003;278:24469-24475.
PubMed DOI: 10.1074/jbc.M301359200
42. Jordà MA, Verbakel SE, Valk PJ, et al. Hematopoietic cells expressing the peripheral cannabinoid receptor migrate in response to the endocannabinoid 2-arachidonoylglycerol. Blood. 2002;99:2786-2793.
PubMed DOI: 10.1182/blood.V99.8.2786
43. Gokoh M, Kishimoto S, Oka S, et al. 2-Arachidonoylglycerol, an endogenous cannabinoid receptor ligand, induces rapid actin polymerization in HL-60 cells differentiated into macrophage-like cells. Biochem J. 2005;386:583-589.
PubMed DOI: 10.1042/BJ20041163
44. Waksman Y, Olson JM, Carlisle SJ, Cabral GA. The central cannabinoid receptor (CB1) mediates inhibition of nitric oxide production by rat microglial cells. J Pharmacol Exp Ther. 1999;288:1357-1366.
PubMed
45. Klegeris A, Bissonnette CJ, McGeer PL. Reduction of human monocytic cell neurotoxicity and cytokine secretion by ligands of the cannabinoid-type CB2 receptor. Br J Pharmacol. 2003;139:775-786.
PubMed DOI: 10.1038/sj.bjp.0705304
46. Facchinetti F, Del Giudice E, Furegato S, Passarotto M, Leon A. Cannabinoids ablate release of TNFα in rat microglial cells stimulated with lypopolysaccharide. Glia. 2003;41:161-168.
PubMed DOI: 10.1002/glia.10177
47. Carrier EJ, Kearn CS, Barkmeier AJ, et al. Cultured rat microglial cells synthesize the endocannabinoid 2-arachidonylglycerol, which increases proliferation via a CB2 receptor-dependent mechanism. Mol Pharmacol. 2004;65:999-1007.
PubMed DOI: 10.1124/mol.65.4.999
48. Derocq J-M, Jbilo O, Bouaboula M, Ségui M, Clère C, Casellas P. Genomic and functional changes induced by the activation of the peripheral cannabinoid receptor CB2 in the promyelocytic cells HL-60: possible involvement of the CB2 receptor in cell differentiation. J Biol Chem. 2000;275:15621-15628.
PubMed DOI: 10.1074/jbc.275.21.15621
49. Devane WA, Hanus L, Breuer A, et al. Isolation and structure of a brain constituent that binds to the cannabinoid receptor. Science. 1992;258:1946-1949.
PubMed
50. Di Marzo V, Fontana A, Cadas H, et al. Formation and inactivation of endogenous cannabinoid anandamide in central neurons. Nature. 1994;372:686-691.
PubMed DOI: 10.1038/372686a0
51. Giuffrida A, Parsons LH, Kerr TM, Rodríguez de Fonseca F, Navarro M, Piomelli D. Dopamine activation of endogenous cannabinoid signaling in dorsal striatum. Nat Neurosci. 1999;2:358-363.
PubMed DOI: 10.1038/7268
52. Walker JM, Huang SM, Strangman NM, Tsou K, Sañudo-Peña MC. Pain modulation by release of the endogenous cannabinoid anandamide. Proc Natl Acad Sci USA. 1999;96:12198-12203.
PubMed DOI: 10.1073/pnas.96.21.12198
53. Di Marzo V, De Petrocellis L, Sugiura T, Waku K. Potential biosynthetic connections between the 2 cannabimimetic eicosanoids, anandamide and 2-arachidonoyl-glycerol, in mouse neuroblastoma cells. Biochem Biophys Res Commun. 1996;227:281-288.
PubMed DOI: 10.1006/bbrc.1996.1501
54. Cadas H, Schinelli S, Piomelli D. Membrane localization of N-acylphosphatidylethanolamine in central neurons: studies with exogenous phospholipases. J Lipid Mediat Cell Signal. 1996;14:63-70.
PubMed DOI: 10.1016/0929-7855(96)00510-X
55. Sugiura T, Kondo S, Sukagawa A, et al. Transacylase-mediated and phosphodiesterase-mediated synthesis of N-arachidonoylethanolamine, an endogenous cannabinoid-receptor ligand, in rat brain microsomes: comparison with synthesis from free arachidonic acid and ehtanolamine Eur J Biochem. 1996;240:53-62.
PubMed
56. Okamoto Y, Morishita J, Tsuboi K, Tonai T, Ueda N. Molecular characterization of a phospholipase D generating anandamide and its congeners. J Biol Chem. 2004;279:5298-5305.
PubMed DOI: 10.1074/jbc.M306642200
57. Piomelli D. The challenge of brain lipidomics. Prostaglandins Other Lipid Mediat. 2005;77:23-34.
PubMed DOI: 10.1016/j.prostaglandins.2004.09.006
58. Calignano A, La Rana G, Giuffrida A, Piomelli D. Control of pain initiation by endogenous cannabinoids. Nature. 1998;394:277-281.
PubMed DOI: 10.1038/28393
59. Felder CC, Nielsen A, Briley EM, et al. Isolation and measurement of the endogenous cannabinoid receptor agonist, anandamide, in brain and peripheral tissues of human and rat. FEBS Lett. 1996;393:231-235.
PubMed DOI: 10.1016/0014-5793(96)00891-5
60. Schmid PC, Kuwae T, Krebsbach RJ, Schmid HHO. Anandamide and other N-acylethanolamines in mouse peritoneal macrophages. Chem Phys Lipids. 1997;87:103-110.
PubMed DOI: 10.1016/S0009-3084(97)00032-7
61. Schmid PC, Paria BC, Krebsbach RJ, Schmid HHO, Dey SK. Changes in anandamide levels in mouse uterus are associated with uterine receptivity for embryo implantation. Proc Natl Acad Sci USA. 1997;94:4188-4192.
PubMed DOI: 10.1073/pnas.94.8.4188
62. Calignano A, Kátona I, Désarnaud F, et al. Bidirectional control of airway responsiveness by endogenous cannabinoids. Nature. 2000;408:96-101.
PubMed DOI: 10.1038/35040576
63. Mackie K, Devane WA, Hille B. Anandamide, an endogenous cannabinoid, inhibits calcium currents as a partial agonist in N18 neuroblastoma cells. Mol Pharmacol. 1993;44:498-503.
PubMed
64. Fride E, Mechoulam R. Pharmacological activity of the cannabinoid receptor agonist, anandamide, a brain constituent. Eur J Pharmacol. 1993;231:313-314.
PubMed DOI: 10.1016/0014-2999(93)90468-W
65. Cravatt BF, Demarest K, Patricelli MP, et al. Supersensitivity to anandamide and enhanced endogenous cannabinoid signaling in mice lacking fatty acid amide hydrolase. Proc Natl Acad Sci USA. 2001;98:9371-9376.
PubMed DOI: 10.1073/pnas.161191698
66. Griffin G, Tao Q, Abood ME. Cloning and pharmacological characterization of the rat CB2 cannabinoid receptor. J Pharmacol Exp Ther. 2000;292:886-894.
PubMed
67. Gonsiorek W, Lunn C, Fan X, Narula S, Lundell D, Hipkin RW. Endocannabinoid 2-arachidonyl glycerol is a full agonist through human type 2 cannabinoid receptor: antagonism by anandamide. Mol Pharmacol. 2000;57:1045-1050.
PubMed
68. Kathuria S, Gaetani S, Fegley D, et al. Modulation of anxiety through blockade of anandamide hydrolysis. Nat Med. 2003;9:76-81.
PubMed DOI: 10.1038/nm803
69. Hampson AJ, Hill WAG, Zan-Phillips M, et al. Anandamide hydroxylation by brain lipoxygenase: metabolite structures and potencies at the cannabinoid receptor. Biochim Biophys Acta. 1995;1259:173-179.
PubMed
70. Yu M, Ives D, Ramesha CS. Synthesis of prostaglandin E2 ethanolamide from anandamide by cyclooxygenase-2. J Biol Chem. 1997;272:21181-21186.
PubMed DOI: 10.1074/jbc.272.34.21181
71. Weber A, Ni J, Ling KH, et al. Formation of prostamides from anandamide in FAAH knockout mice analyzed by HPLC with tandem mass spectrometry. J Lipid Res. 2004;45:757-763.
PubMed DOI: 10.1194/jlr.M300475-JLR200
72. Kim J, Alger BE. Inhibition of cyclooxygenase-2 potentiates retrograde endocannabinoid effects in hippocampus. Nat Neurosci. 2004;7:697-698.
PubMed DOI: 10.1038/nn1262
73. Mechoulam R, Ben-Shabat S, Hanus L, et al. Identification of an endogenous 2-monoglyceride, present in canine gut, that binds to cannabinoid receptors. Biochem Pharmacol. 1995;50:83-90.
PubMed DOI: 10.1016/0006-2952(95)00109-D
74. Sugiura T, Kondo S, Sukagawa A, et al. 2-arachidonoylglycerol: a possible endogenous cannabinoid receptor ligand in brain. Biochem Biophys Res Commun. 1995;215:89-97.
PubMed DOI: 10.1006/bbrc.1995.2437
75. Stella N, Schweitzer P, Piomelli D. A second endogenous cannabinoid that modulates long-term potentiation. Nature. 1997;388:773-778.
PubMed DOI: 10.1038/42015
76. Prescott SM, Majerus PW. Characterization of 1,2-diacylglycerol hydrolysis in human platelets: demonstration of an arachidonoyl-monoacylglycerol intermediate. J Biol Chem. 1983;258:764-769.
PubMed
77. Farooqui AA, Taylor AW, Horrocks LA. Separation of bovine brain mono- and diacylglycerol lipases by heparin sepharose affinity chromatography. Biochem Biophys Res Commun. 1984;122:1241-1246.
PubMed DOI: 10.1016/0006-291X(84)91225-7
78. Maejima T, Oka S, Hashimotodani Y, et al. Synaptically driven endocannabinoid release requires Ca2+-assisted metabotropic glutamate receptor subtype 1 to phospholipase Cbeta4 signaling cascade in the cerebellum. J Neurosci. 2005;25:6826-6835.
PubMed DOI: 10.1523/JNEUROSCI.0945-05.2005
79. Hashimotodani Y, Ohno-Shosaku T, Tsubokawa H, et al. Phospholipase Cbeta serves as a coincidence detector through its Ca2+ dependency for triggering retrograde endocannabinoid signal. Neuron. 2005;45:257-268.
PubMed DOI: 10.1016/j.neuron.2005.01.004
80. Bisogno T, Howell F, Williams G, et al. Cloning of the first sn1-DAG lipases points to the spatial and temporal regulation of endocannabinoid signaling in the brain. J Cell Biol. 2003;163:463-468.
PubMed DOI: 10.1083/jcb.200305129
81. Bisogno T, Sepe N, Melck D, Maurelli S, De Petrocellis L, Di Marzo V. Biosynthesis, release and degradation of the novel endogenous cannabimimetic metabolite 2-arachidonoylglycerol in mouse neuroblastoma cells. Biochem J. 1997;322:671-677.
PubMed
82. Bisogno T, Maccarrone M, De Petrocellis L, et al. The uptake by cells of 2-arachidonoylglycerol, an endogenous agonist of cannabinoid receptors. Eur J Biochem. 2001;268:1982-1989.
PubMed DOI: 10.1046/j.1432-1327.2001.02072.x
83. Beltramo M, Piomelli D. Carrier-mediated transport and enzymatic hydrolysis of the endogenous cannabinoid 2-arachidonylglycerol. Neuroreport. 2000;11:1231-1235.
PubMed
84. Dinh TP, Carpenter D, Leslie FM, et al. Brain monoglyceride lipase participating in endocannabinoid inactivation. Proc Natl Acad Sci USA. 2002;99:10819-10824.
PubMed DOI: 10.1073/pnas.152334899
85. Dinh TP, Kathuria S, Piomelli D. RNA interference suggests a primary role for monoacylglycerol lipase in the degradation of the endocannabinoid 2-arachidonoylglycerol. Mol Pharmacol. 2004;66:1260-1264.
PubMed DOI: 10.1124/mol.104.002071
86. Kozak KR, Rowlinson SW, Marnett LJ. Oxygenation of the endocannabinoid, 2-arachidonylglycerol, to glyceryl prostaglandins by cyclooxygenase-2. J Biol Chem. 2000;275:33744-33749.
PubMed DOI: 10.1074/jbc.M007088200
87. Goparaju SK, Ueda N, Yamaguchi H, Yamamoto S. Anandamide amidohydrolase reacting with 2-arachidonoylglycerol, another cannabinoid receptor ligand. FEBS Lett. 1998;422:69-73.
PubMed DOI: 10.1016/S0014-5793(97)01603-7
88. Breivogel CS, Griffin G, Di Marzo V, Martin BR. Evidence for a new G protein-coupled cannabinoid receptor in mouse brain. Mol Pharmacol. 2001;60:155-163.
PubMed
89. Di Marzo V, Breivogel CS, Tao Q, et al. Levels, metabolism, and pharmacological activity of anandamide in CB1 cannabinoid receptor knockout mice: evidence for non-CB1, non-CB2 receptor-mediated actions of anandamide in mouse brain. J Neurochem. 2000;75:2434-2444.
PubMed DOI: 10.1046/j.1471-4159.2000.0752434.x
90. Hájos N, Ledent C, Freund TF. Novel cannabinoid-sensitive receptor mediates inhibition of glutamatergic synaptic transmission in the hippocampus. Neuroscience. 2001;106:1-4.
PubMed DOI: 10.1016/S0306-4522(01)00287-1
91. Hájos N, Freund TF. Pharmacological separation of cannabinoid sensitive receptors on hippocampal excitatory and inhibitory fibers. Neuropharmacology. 2002;43:503-510.
PubMed DOI: 10.1016/S0028-3908(02)00157-0
92. Hoffman AF, Macgill AM, Smith D, Oz M, Lupica CR. Species and strain differences in the expression of a novel glutamate-modulating cannabinoid receptor in the rodent hippocampus. Eur J Neurosci. 2005;22:2387-2391.
PubMed DOI: 10.1111/j.1460-9568.2005.04401.x
93. Rouach N, Nicoll RA. Endocannabinoids contribute to short-term but not long-term mGluR-induced depression in the hippocampus. Eur J Neurosci. 2003;18:1017-1020.
PubMed DOI: 10.1046/j.1460-9568.2003.02823.x
94. Pistis M, Perra S, Pillolla G, Melis M, Gessa GL, Muntoni AL. Cannabinoids modulate neuronal firing in the rat basolateral amygdala: evidence for CB1- and non-CB1-mediated actions. Neuropharmacology. 2004;46:115-125.
PubMed DOI: 10.1016/j.neuropharm.2003.08.003
95. Houser SJ, Eads M, Embrey JP, Welch SP. Dynorphin B and spinal analgesia: induction of antinociception by the cannabinoids CP55,940, Delta(9)-THC and anandamide. Brain Res. 2000;857:337-342.
PubMed DOI: 10.1016/S0006-8993(00)01981-8
96. Welch SP, Huffman JW, Lowe J. Differential blockade of the antinociceptive effects of centrally administered cannabinoids by SR141716A. J Pharmacol Exp Ther. 1998;286:1301-1308.
PubMed
97. Begg M, Pacher P, Batkai S, et al. Evidence for novel cannabinoid receptors. Pharmacol Ther. 2005;106:133-145.
PubMed DOI: 10.1016/j.pharmthera.2004.11.005
98. Járai Z, Wagner JA, Varga K, et al. Cannabinoid-induced mesenteric vasodilation through an endothelial site distinct from CB1 or CB2 receptors. Proc Natl Acad Sci USA. 1999;96:14136-14141.
PubMed DOI: 10.1073/pnas.96.24.14136
99. Offertáler L, Mo F, Bátkai S, et al. Selective ligands and cellular effectors of a G protein-coupled endothelial cannabinoid receptor. Mol Pharmacol. 2003;63:699-705.
PubMed DOI: 10.1124/mol.63.3.699
100. Begg M, Mo F-M, Offertáler L, et al. G protein-coupled endothelial receptor for atypical cannabinoid ligands modulates a Ca2+-dependent K+ current. J Biol Chem. 2003;278:46188-46194.
PubMed DOI: 10.1074/jbc.M307258200
101. Bouaboula M, Rinaldi M, Carayon P, et al. Cannabinoid-receptor expression in human leukocytes. Eur J Biochem. 1993;214:173-180.
PubMed DOI: 10.1111/j.1432-1033.1993.tb17910.x
102. Klein TW, Newton C, Larsen K, et al. The cannabinoid system and immune modulation. J Leukoc Biol. 2003;74:486-496.
PubMed DOI: 10.1189/jlb.0303101
103. Walter L, Stella N. Cannabinoids and neuroinflammation. Br J Pharmacol. 2004;141:775-785.
PubMed DOI: 10.1038/sj.bjp.0705667
104. Lambert DM, Vandevoorde S, Jonsson K-O, Fowler CJ. The palmitoylethanolamide family: a new class of anti-inflammatory agents? Curr Med Chem. 2002;9:663-674.
PubMed
105. Jaggar SI, Hasnie FS, Sellaturay S, Rice AS. The anti-hyperalgesic actions of the cannabinoid anandamide and the putative CB2 receptor agonist palmitoylethanolamide in visceral and somatic inflammatory pain. Pain. 1998;76:189-199.
PubMed DOI: 10.1016/S0304-3959(98)00041-4
106. Cadas H, di Tomaso E, Piomelli D. Occurrence and biosynthesis of endogenous cannabinoid precursor, N-arachidonoyl phosphatidylethanolamine, in rat brain. J Neurosci. 1997;17:1226-1242.
PubMed
107. Hansen HS, Lauritzen L, Strand AM, Vinggaard AM, Frandsen A, Schousboe A. Characterization of glutamate-induced formation of N-acylphosphatidylethanolamine and N-acylethanolamine in cultured neocortical neurons. J Neurochem. 1997;69:753-761.
PubMed
108. Stella N, Piomelli D. Receptor-dependent formation of endogenous cannabinoids in cortical neurons. Eur J Pharmacol. 2001;425:189-196.
PubMed DOI: 10.1016/S0014-2999(01)01182-7
109. Walter L, Franklin A, Witting A, Möller T, Stella N. Astrocytes in culture produce anandamide and other acylethanolamides. J Biol Chem. 2002;277:20869-20876.
PubMed DOI: 10.1074/jbc.M110813200
110. Walter L, Stella L. Endothelin-1 increases 2-arachidonyl glycerol (2-AG) production in astrocytes. Glia. 2003;44:85-90.
PubMed DOI: 10.1002/glia.10270
111. Franklin A, Parmentier-Batteur S, Walter L, Greenberg DA, Stella N. Palmitoylethanolamide increases after focal cerebral ischemia and potentiates microglial cells motility. J Neurosci. 2003;23:7767-7775.
PubMed
112. Ueda N, Yamanaka K, Yamamoto S. Purification and characterization of an acid amidase selective for N-palmitoylethanolamine, a putative endogenous anti-inflammatory substance. J Biol Chem. 2001;276:35552-35557.
PubMed DOI: 10.1074/jbc.M106261200
113. Tsuboi K, Sun YX, Okamoto Y, Araki N, Tonai T, Ueda N. Molecular characterization of N-acylethanolamine-hydrolyzing acid amidase, a novel member of the choloylglycine hydrolase family with structural and functional similarity to acid ceramidase. J Biol Chem. 2005;280:11082-11092.
PubMed DOI: 10.1074/jbc.M413473200
114. Ueda N, Tsuboi K, Lambert DM. A second N-acylethanolamine hydrolase in mammalian tissues. Neuropharmacology. 2005;48:1079-1085.
PubMed DOI: 10.1016/j.neuropharm.2004.12.017
115. Sun YX, Tsuboi K, Zhao LY, Okamoto Y, Lambert DM, Ueda N. Involvement of N-acylethanolamine-hydrolyzing acid amidase in the degradation of anandamide and other N-acylethanolamines in macrophages. Biochim Biophys Acta. 2005;1736:211-220.
PubMed
116. Gulyas AI, Cravatt BF, Bracey MH, et al. Segregation of 2 endocannabinoid-hydrolyzing enzymes into pre- and postsynaptic compartments in the rat hippocampus, cerebellum and amygdala. Eur J Neurosci. 2004;20:441-458.
PubMed DOI: 10.1111/j.1460-9568.2004.03428.x
117. Sawzdargo M, Nguyen T, Lee DK, et al. Identification and cloning of three novel human G protein-coupled receptor genes GPR52, PsiGPR53 and GPR55: GPR55 is extensively expressed in human brain. Brain Res Mol Brain Res. 1999;64:193-198.
PubMed DOI: 10.1016/S0169-328X(98)00277-0
118. Brown A, Wise A, inventors. GlaxoSmithKline, assignee. Identification of modulators of GPR55 activity. US patent 0 113 814. June 19, 2003.
119. Drmota T, Greasley P, Groblewski T, inventors. AstraZeneca, assignee. Screening assays for cannabinoid-ligand-type modulators of GPR55. WIPO patent 074 844. September 2, 2004.
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It is now well established that the psychoactive effects of Cannabis sativa are primarily mediated through neuronal CB1 receptors, while its therapeutic immune properties are primarily mediated through CB2 receptors. Two endocannabinoids, arachidonoylethanolamide and 2-arachidonoylglycerol, have been identified, their action on CB1 and CB2 thoroughly characterized, and their production and inactivation elucidated. However, many significant exceptions to these rules exist. Here we review the evidence suggesting that cannabinoids can modulate synaptic transmission, the cardiovascular system, and the immune system through receptors distinct from CB1 and CB2, and that an additional “independent” endocannabinoid signaling system that involves palmitoylethanolamide may exist.
Introduction
Cannabis sativa, also known as marijuana or hashish depending on the particular preparation, is both a widespread illegal drug of abuse and a well-recognized medicinal plant.1,2 A current challenge in pharmacology is to increase our understanding of the molecular mechanisms underlying the abuse property of C sativa in order to develop means to prevent it. Another challenge is to isolate the bioactive components that impart the medicinal properties ascribed to this plant with the goal of developing novel, cannabinoid-based therapeutics devoid of adverse effects. After approximately 40 years of research, we have a much clearer understanding of the pharmacology and molecular mechanisms mediating the bioactivity of plant-derived cannabinoid compounds, the phytocannabinoids, and are getting much closer to overcoming these 2 challenges.
C sativa contains ~60 phytocannabinoids, a handful of which are bioactive as defined by their ability to specifically interact with membrane-associated receptors, the cannabinoid receptors. The best-known phytocannabinoid is ∆9-tetrahydrocannabinol (THC),3 which is thought to mediate most—if not all—of the psychotropic and addictive properties of C sativa.4 Recent evidence suggest that some of the antiinflammatory properties of C sativa may be accounted for by cannabinol (CBN) and cannabidiol (CBD), 2 nonpsychotropic phytocannabinoids that constitute promising lead compounds to develop cannabinoid-based antiinflammatory medicines.5,6 Thus, while some might focus on THC to study the psychotropic and addictive properties of C sativa, others might focus on CBN and CBD as a means to develop cannabinoid-based antiinflammatory therapeutics devoid of adverse effects. Here we will review our current understanding of the cannabinoid receptors that mediate the effects of cannabinoids and provide examples of the biological functions regulated by them, with a special emphasis on those receptors that have been pharmacologically characterized and yet still remain to be cloned. We will also review our current understanding of the endogenous cannabinoids, the endocannabinoids, with a special emphasis on palmitoylethanolamide (PEA), whose production and inactivation can occur independently of other endocannabinoids, and whose biological effects are mediated by interactions with one of the novel cannabinoid receptors.
Cannabinoids Activate at Least 5 Distinct Cannabinoid Receptors
Two cannabinoid receptors, CB1 and CB2, have been identified by molecular cloning and are unambiguously established as mediators of the biological effects induced by cannabinoids, either plant derived, synthetic, or endogenously produced. CB1 and CB2 are 7 transmembrane Gi/o-coupled receptors that share 44% protein identity and display different pharmacological profiles and patterns of expression,7,8 a dichotomy that provides a unique opportunity to develop pharmaceutical approaches. Studies performed with CB1−/− and/or CB2−/− mice identified additional cannabinoid receptors, 3 of which will be discussed below.
CB1 Receptors
The vast majority of CB1 receptors are expressed in the central nervous system (CNS), and their distribution in this tissue has been documented in detail using highly specific antibodies and CB1−/− tissue controls. The current picture depicts abundant presynaptic expression in the adult mammalian brain.9 In some cases, these receptors are also present on the dendrites and soma of neurons,10 although at lower levels and frequency than their presynaptic counterparts. CB1 receptors are also expressed at low levels by various astrocytes, oligodendrocytes, and neural stem cells.11-13 To the best of our knowledge, expression of CB1 receptors in situ by ependymal cells and/or microglia has not been reported.
CB1 receptors couple to Gi/o proteins and, under specific conditions, also to Gs proteins (only when other Gi/o protein-coupled receptors are concomitantly activated).14,15 By coupling to Gi/o proteins, CB1 receptors regulate the activity of many plasma membrane proteins and signal transduction pathways, including ion channels, enzymes producing cyclic nucleotide second messengers, and various kinases. Thus, depending on the coupling and cell type expressing CB1 receptors, cannabinoids may regulate distinct cell functions. For example, activation of presynaptic CB1 receptors inhibits N-type calcium channels, thus reducing synaptic transmission.9 It is likely that THC induces most—if not all—of its acute cognitive and intoxicating effects through this molecular mechanism.16 Whether THC produces its effect by partially activating CB1 receptors or antagonizing the action of endocannabinoids on this receptor remains an open question.17,18 Activation of CB1 receptors expressed on the somata of neurons increases Erk activity and induces brain-derived neurotrophic factor (BDNF) expression.10 It is likely that the neuroprotective properties of cannabinoids are in part mediated through this mechanism. Recent evidence shows that CB1 receptor may also control the fate of neural stem cells, the outgrowth of neurites and the formation of functional synapses, emphasizing the importance of this receptor in the remodeling of neuronal networks.13,19-21 Note that blood-derived leukocytes also express CB1 receptors,22 suggesting that under neuropathological conditions, whereby the blood brain barrier is disrupted, cannabinoids accumulating in the CNS likely activate CB1 receptors expressed by invading leukocytes and thereby modulate the development of neuroinflammation.23-25
CB2 Receptors
Under nonpathological conditions, CB2 receptors are primarily expressed by leukocytes (with a rank order of B cells > natural killer [NK] cells >> monocytes/macrophages > neutrophils > CD8+ T cells > CD4+ T cells). Furthermore, experiments performed with CB2−/− mice show that cannabinoids engaging these receptors lead to changes in immune responses, particularly at the level of macrophage-induced helper T-cell activation.8,22,26 CBN is more efficacious at CB2 receptors than THC,27 making this phytocannabinoid more likely to account for the antiinflammatory properties of C sativa. For example, activation of CB2 receptors inhibits the ability of macrophages to process antigens and prime helper T cells26,28-31 and at high concentrations may induce immune cell apoptosis.32
While many laboratories have reported the absence of CB2 receptor expression in healthy brain,8,22,33-36 a new study has found that neurons located in specific brain structures, such as the brain stem, express detectable levels of CB2 mRNA and functional receptors, the activation of which is thought to regulate emesis.37 Furthermore, while resting microglia present in healthy CNS tissue express few—if any—CB2 receptors, activated microglial cells, such as those found in mouse models of multiple sclerosis and Alzheimer’s disease, express significant levels of CB2 receptors.38,39 This result is not surprising since pathological conditions are known to induce CB2 receptor expression in leukocytes.36 Microglial cells in culture, which by default are considered chronically activated, also express CB2 receptors, particularly at the leading edges of lamellipodia, protrusions involved in cell migration.40 Accordingly, application of CB2 agonists induces cell migration, a response that can be extended to other CB2-expressing cells.41-43 Furthermore, several laboratories have shown that CB2 agonists reduce the release of cytotoxins by immune cells and increase their proliferation rate.44-47 Taken together, these studies suggest that the ability of CB2-selective compounds to reduce inflammation might be caused by an increase in proliferation and recruitment of immune cells, in particular a population of immune cells that do not release detrimental mediators and thus could be involved in the immune-mediated repair of damaged tissue. Again, blood-derived leukocytes expressing CB2 receptors and invading the CNS via a disrupted blood brain barrier are likely to be activated by cannabinoids accumulating in the CNS and to modulate the development of neuroinflammation. Whether astrocytes and endothelial cells express CB2 receptors remains controversial as control experiments using CB2−/− tissue have yet to be performed.
Similar to CB1 receptors, CB2 receptors also couple to Gi/o proteins and regulate the activity of signal transduction pathways, including enzymes that produce cyclic nucleotide second messengers and various kinases. Accordingly, increased Erk activity via activation of CB2 receptors induces immune cell migration and changes in gene expression.40,48 When expressed in AtT-20 cells, CB2 receptors do not modulate ion conductances, making this function unique to CB1 receptors.27 This result poses an intriguing question: considering that some neurons express CB2 receptors, does activation of this receptor affect the firing rate of these neurons and, if so, through what signal transduction pathway?
Two Endocannabinoids
The existence of cannabinoid receptors and the biological effects induced by cannabinoids suggests the existence of endocannabinoids that normally engage these receptors. Arachidonoylethanolamide (AEA), also known as anandamide, was identified in 1992 by Devane and colleagues and shown to bind with high affinity to CB1 receptors.49 Since then, AEA has been extensively studied and shown to fulfill the 3 criteria necessary to be considered a bona fide endocannabinoid: (1) activity-dependent production, (2) functional activation of cannabinoid receptors, and (3) biological inactivation.
Activity-dependent production of AEA was demonstrated in neurons in primary culture and in the brain of freely moving rats using microdialysis.50-52 The molecular mechanism underlying AEA biosynthesis and hydrolysis is beginning to be understood. Depending on the cell type, stimuli that increase intracellular concentrations of calcium increase AEA production.50,53 Calcium-dependent increases in AEA production are likely mediated through calcium-dependent increases in the activity of acyltransferase, the enzyme that generates the AEA precursor N-arachidonylphosphatidylethanolamide (NAPE).54,55 A recently cloned NAPE-phospholipase D may be responsible for cleaving this precursor.56 Thus, unlike classical transmitter substances, AEA is produced upon demand by enzymatic cleavage of membrane lipid precursors and immediately extruded from cells without an intermediate step of vesicle storage, a feature reminiscent of other lipid-derived mediators.57 AEA production is not restricted to neurons since many different cell types, including astrocytes and microglial cells, also produce this ligand.40,58-62
AEA activates the signal transduction pathways coupled to CB1 receptors, although it has a low intrinsic efficacy.63 Injection of AEA into rodents mimics most of the effects produced by THC,64 although inactivation of its degradation is often necessary to see biological effects.65 AEA also binds CB2 receptors, acting as a partial agonist, or antagonist,66,67 effects that might have some relevance in modulating inflammation.
Strong genetic and pharmacological evidence has demonstrated that fatty acid amide hydrolase (FAAH) inactivates AEA.65,68 Of interest, other enzymes may also metabolize AEA, including cyclooxygenases and lipooxygenases.69,70 Their respective involvement in AEA inactivation in intact cells, especially when FAAH is also expressed, is starting to be unraveled.71,72
In 1995, the laboratories of Raphael Mechoulam and Keizo Waku simultaneously reported a second endogenous ligand, 2-arachidonylglycerol (2-AG).73,74 Neuronal activity enhances 2-AG synthesis, its levels reaching 100 times that of AEA.75 While classic studies have shown that 2-AG is produced through the phospholipase C (PLC)/diacylglycerol lipase (DGL) pathway,76,77 more recent genetic studies show that PLCβ1 and PLCβ4 mediate 2-AG biosynthesis in pyramidal and Purkinje neurons, respectively,78,79 and that there exist 2 subtypes, α and β, of DGL directly controlling its biosynthesis.80
2-AG activates CB1 and CB2 receptors with distinct pharmacological profiles, is carried into cells by a “yet-to-be” cloned transporter, and is inactivated by monoacylglycerol lipase (MGL).81-84 When MGL protein is fully knocked down by RNA interference (RNAi), 50% of the 2-AG hydrolyzing activity remains in cell homogenates, indicating that additional enzymes may hydrolyze this lipid.85 Prime candidates are FAAH and the cyclooxygenases.86,87
In summary and as a first approximation, psychoactive effects of cannabis are primarily mediated by neuronal CB1 receptors, while immune effects are primarily mediated by CB2 receptors. Two endocannabinoids have been identified, their action on either CB1 or CB2 is thoroughly characterized, and their production and inactivation elucidated; however, many significant exceptions to these rules exist. Indeed, convincing evidence now suggests that specific cannabinoid effects on synaptic transmission, the cardiovascular system, and immune system are mediated by cannabinoid receptors distinct from CB1 and CB2, and that additional “independent” endocannabinoids exist. Below we will briefly review this evidence.
Non-CB1/CB2 Receptors on Neurons
Three sets of experiments, each using the approach of applying cannabinoids to CB1−/− mice, support the existence of non-CB1/CB2 receptors regulating synaptic transmission. The first were experiments examining GTPγS binding in brain membranes prepared from CB1−/− mice. Breivogel and colleagues found that AEA and the aminoalkylindole WIN55,212-2 stimulated GTPγS binding in brain homogenates prepared from these mice.88,89 The regional distribution of GTPγS binding only partially overlapped those of CB1 or CB2 receptors, emphasizing that these novel receptors likely have a distinct physiological role. Furthermore, this novel receptor was stimulated by WIN55,212-2 and anandamide but not by CP55,940, HU210, or THC and was only weakly antagonized by SR141716A, emphasizing a pharmacology divergent from CB1 and CB2.
The second set of experiments supporting the existence of non-CB1/CB2 cannabinoid receptor(s) examined glutamatergic transmission in CA1 of mouse hippocampus.90,91 Hájos and colleagues found that WIN55,212-2 and CP55,940 inhibited excitatory transmission with equal efficacy in wild-type and CB1−/− mice. Of interest, a recent report showed that while CD1 mice had this response, the C57BL-6 strain did not.92 This inhibitory effect of WIN55212-2 and CP55940 was abolished by SR141716 and capsazepine but was unaffected by the SR141716 analog, AM251.90 As WIN55,212-2 and CP55,940 do not interact with TRPV1 channels, it is unlikely that TRPV1 mediates this response. Additional evidence suggested that these novel receptors are involved in endocannabinoid-mediated short-term plasticity. Specifically, Rouach and Nicoll93 found that activation of group I metabotropic glutamate receptors in CB1−/− mice causes short-term depression of excitatory transmission in the hippocampal CA1 region that is blocked by SR141716. A pharmacologically similar receptor is also present on amygdala projection neurons, and this novel receptor likely plays a role in anxiety, as shown by antagonist experiments in rodents.94
The third set of experiments examined the analgesic efficacy of THC in spinal cord. Welch and coworkers found that the rank order potency of SR141716A in blocking analgesia produced by THC, anandamide, and CP55,490 differed from that predicted by a CB1-mediated response.95,96 In addition, there were also differences in the synergy between morphine and THC compared with morphine and AEA or CP55,940, suggesting the involvement of a novel receptor.
Non-CB1/CB2 Receptors in the Vasculature
Very strong evidence for non-CB1/CB2 cannabinoid receptors comes from a continuing series of investigations performed by several laboratories studying the effects of cannabinoids on the vasculature.97 Essentially the findings are that certain cannabinoids cause vasodilation and hypotension in the absence of CB1, CB2, or TRPV1 receptor activation. The best-characterized response is in mesenteric vessels,98 in which AEA and its analog methanandamide cause vasodilation, while synthetic cannabinoids and THC do not. This response is sensitive to high concentrations (>1 µM) of SR141716A. Similar to the inhibitory effect on hippocampal glutamatergic transmission described above, the SR141716A analog AM251 does not antagonize this novel receptor. The response is, however, sensitive to pertussis toxin, implicating Gi or Go proteins in the signaling pathway. An important pharmacological tool for non-CB1/CB2 cannabinoid receptors that emerged from these studies is the cannabidiol analog, abnormal cannabidiol (abn-CBD).98 Abn-CBD functions as an agonist at some of these novel cannabinoid receptors, is inactive at CB1 and CB2 receptors, and is antagonized by both cannabidiol and O-1918, a synthetic cannabidiol analog.99 Several lines of evidence suggest that endothelial cells express this novel cannabinoid receptor, and its activation leads to the release of nitric oxide, culminating in the opening of potassium channels on vascular smooth muscle and leading to relaxation and vasodilation.100 Although there are strong pharmacological parallels between the vascular and hippocampal novel receptors, there are some notable differences. For example, the vascular receptor is insensitive to potent synthetic cannabinoids. It is possible that such differences arise from distinct receptor entities, the specific cellular context in which the receptor is expressed or receptor dimerization.
Non-CB1/CB2 Receptors on Immune Cells
Immune cells express both CB1 and CB2 receptors, the levels of which vary depending on the activation state of immune cells. For example, while mature B cells express high levels of CB1 and CB2 receptors, naïve T cells express very low levels of either receptor.101 Strong evidence suggests that cannabinoids interact with CB1 and CB2 receptors expressed by immune cells, increasing their proliferation rate and survival, while inhibiting the production of various immune mediators such as cytokines.102,103 As such, many of the therapeutic, anti-inflammatory properties attributed to C sativa intake likely occur through this mechanism. Yet recent convincing evidence shows that immune cells likely express at least one additional cannabinoid receptor. These experiments were performed with palmitoylethanolamide (PEA, an analog of anandamide that contains a 16:0 fatty acid moiety instead of 20:4 for AEA), which has received considerable attention because of its antiinflammatory properties.104 Piomelli and colleagues, and, simultaneously, Rice and colleagues, found that PEA reduces the pain associated with an inflammatory response.58,105 This analgesic effect of PEA likely involves a novel cannabinoid receptor because SR144528, a well-characterized CB2 antagonist, blocked the analgesia, yet PEA does not bind to CB2 receptors.66 Two hypotheses stem from these results: (1) PEA might interact with a novel cannabinoid receptor that is antagonized by SR144528 (thus this antagonist is not specific for CB2 receptors), or (2) PEA might stimulate a novel cannabinoid receptor that couples to phospholipases C and diacylglycerol lipase, increases 2-AG production, and thus indirectly activates CB2 receptors. Currently, the signal transduction pathway(s) coupled to the novel PEA-sensitive receptor is unknown.
PEA: An Independent Endocannabinoid?
Results showing that PEA interacts with a distinct non-CB1/CB2 receptor suggest that this lipid might constitute a unique “parallel” endocannabinoid signaling system. Providing support to this concept is the evidence that PEA production and inactivation can occur independently of AEA and 2-AG production and inactivation. Specifically, in rodent cortical neurons, general activity-dependent production of AEA, 2-AG, and PEA occurs concomitantly.50,106,107 Yet, subsequent studies showed that 2-AG production can be increased independently when N-methyl-D-aspartate (NMDA) receptors are activated, while increased AEA and PEA production requires addition of carbachol.108 A more detailed pharmacological study showed that activation of nicotinic receptors increases AEA production, while activation of muscarinic receptors increases PEA production. Thus, although biosynthesis of all endocannabinoids in this model system is contingent on NMDA-receptor occupation, increased AEA production requires the co-activation of α7 nicotinic receptors, while increased PEA production requires the co-activation of muscarinic receptors. This finding suggests that glutamate and acetylcholine may elicit the biosynthesis of different endocannabinoids depending on the complement of cholinergic receptors expressed in their target neurons. Additional evidence for independent production of AEA, 2-AG, and PEA comes from experiments performed on mouse astrocytes in culture. In this model, the calcium ionophore ionomycin and the peptide endothelin-1 increase the production of both AEA and 2-AG, while PEA levels remain unchanged.109,110 The notion that PEA might be independently produced also holds true in vivo.111 For example, in the case of focal cerebral ischemia, PEA levels in ischemic cerebral cortex increase ~25-fold compared with sham-operated animals, while AEA levels increase by barely 3-fold and 2-AG levels remain unchanged.
Novel evidence shows that PEA inactivation can also occur independently from that of AEA and 2-AG. The laboratory of Natsuo Ueda discovered the existence of a unique enzyme capable of hydrolyzing PEA to much greater extent than AEA and 2-AG. The original observation was obtained with homogenates prepared from human megakaryoblastic cells (CMK), in which AEA hydrolysis occurred with low activity and a strikingly different pH profile from that of FAAH.112 Specifically, while FAAH is known to maximally hydrolyze AEA at pH 9 (with this activity dropping by 70% at pH 5), CMK cells were shown to maximally hydrolyze AEA at pH 5 (with this activity dropping by 95% at pH 9). Using an elegant 4-step purification approach, Ueda and colleagues were able to purify this novel enzymatic activity by 760-fold, obtain partial protein sequence, and clone a cDNA encoding this protein, which was named N-acylethanolamine-hydrolyzing acid amidase (NAAA).113 When assessing its substrate specificity, it became clear that this enzyme preferred PEA over AEA (having hydrolytic activities toward these substrates of 8 and 0.25 nmol/min/mg, respectively). Besides a distinct pH profile and substrate specificity, NAAA has additionally very interesting properties. It is highly expressed in spleen and thymus, as well as in macrophages homing to the lungs and small intestine, highlighting its potential importance in regulating PEA signaling in the context of immunobiology. Here, it should be emphasized that NAAA expression and activity are quite low in healthy brain.113
The laboratory of Didier Lambert developed a competitive inhibitor of NAAA, N-cyclohexanecarbonylpentadecylamine, which has an IC50 of 5 µM and is inactive against FAAH at 100 µM.114 When considering that methyl arachidonoyl fluorophosphonate (MAFP) and URB597 inhibit FAAH with nanomolar IC50s and are both inactive against NAAA at a concentration of 1 µM, experiments designed to use these compounds in combination may be useful to distinguish the biological importance of either PEA or AEA hydrolysis in various biological responses.114,115
This series of studies raises many fascinating questions: for example, “What is the subcellular location of NAAA and does it differ from FAAH?” The pH profile of NAAA is quite intriguing. With maximal NAAA activity occurring at pH 5 and only 10% of this activity remaining at pH 7 (ie, the cytosolic pH), one wonders if NAAA might be active only in lysosomes. Accordingly, NAAA-GFP (green fluorescent protein) fusion protein localized to lysosome-like vesicles.113 This result is quite interesting when considering that FAAH is also abundant in intracellular organelles such as mitochondria and the smooth endoplasmic reticulum.116 Clearly, elucidating the exact biological role of NAAA will be facilitated by genetic studies similar to those performed on FAAH. Finally, while AEA and 2-AG hydrolysis give rise to new bioactive lipids (ie arachidonic acid and eicosanoids), PEA hydrolysis gives rise to 2 relatively inactive products, palmitic acid and ethanolamine, suggesting that the role of NAAA is to truly stop biological responses initiated by increases in PEA production.
Is GPR55 the Cannabinoid Receptor Engaged by PEA?
GPR55 was first identified as an orphan G protein coupled receptor (GPCR) enriched in brain.117 Its gene is located on chromosome 2 (location: 2q37) in mice and chromosome 6 in humans, and its open reading frame encodes a relatively short 319 amino acid protein. Using Northern blot analysis of human tissues, GPR55 mRNA was found in caudate and putamen, but not in frontal cortex, hippocampus, thalamus, pons, cerebellum, or liver.117 Northern blot analysis of rat tissues showed GPR55 mRNA in spleen, fetal tissues, and intestine. Further in situ hybridization studies found GPR55 mRNA in rat hippocampus, thalamus, and midbrain.117 The difference between the human and rat CNS studies may represent sensitivity differences between the 2 specific techniques, or a variation between species, and invites further careful study. A more thorough distribution of human GPR55 mRNA has been reported in the patent literature. A first patent reported the following relative abundance: adipose > testis > myometrium > adenoid = tonsil > spleen > ilium > brain = stomach.118 Low levels were found in other tissues. Synthesis of the above results emphasizes that GPR55 is highly expressed in tissues known to respond to cannabinoids.
A very recent second patent application argued that GPR55 might constitute an additional cannabinoid receptor subtype.119 The main findings are as follows: human GPR55 amplified from genomic DNA contains an 11 amino acid substitution in distal intracellular loop 2 and the fourth transmembrane domain not present in the originally reported GPR55 sequence. This variant was termed GPR55A and corresponds to the Human Genome Project sequence. Phylogenetically, GPR55 is closest in sequence to the platelet activating factor (PAF) purinergic P2Y9 and 2 orphan receptors GPR35 and GPR92. It has reasonable homology to several other very interesting GPCR, including P2Y5 and CCR4. It only shares 13.5% and 14.4% homology with CB1 and CB2, respectively. When expressed in HEK293 cells, GPR55A bound CP55,940 and SR141716A, but not WIN55,212-2. Signal transduction was examined using GTPγS binding. A wide range of cannabinoid compounds stimulated GTPγS binding, including THC, anandamide, 2-AG, virodhamine, and CP55,940, all with EC50 values less than 20 nM. Most remarkably, PEA also stimulated GTPγS binding with even lower nM potency. This latter result suggests the exciting possibility that GPR55 may mediate the antiinflammatory effects of PEA discussed above. Pretreatment of GPR55A expressing HEK293 membranes with pertussis toxin or cholera toxin did not alter CP55,940 stimulation of GTPγS binding, indicating that, in contrast to CB1 and CB2 receptors, GPR55A does not activate Gi, Go, or Gs proteins, at least in HEK293 cells. Thus, GPR55(A) represents a new subtype of cannabinoid receptor with ligand binding and signaling profiles distinct from those of CB1 and CB2.
Conclusion
The results discussed above clearly argue for the existence of multiple cannabinoid receptors, specifically the cloned CB1 and CB2 receptors, and at least 3 non-CB1/CB2 cannabinoid receptors. Owing to their expression profile and coupling mechanism, each receptor likely mediates distinct effects of phytocannabinoids and endocannabinoids. In addition, strong evidence implicates PEA as an inflammatory modulator acting via a non-CB1/CB2 cannabinoid receptor. While recent data suggest that this latter receptor might be GPR55, many key experiments remain to be done, such as determining the precise pharmacology of this receptor, its coupling capabilities and expression pattern. The existence of different enzymatic routes for the formation of AEA, 2-AG, and PEA suggests that these endocannabinoids may operate independently from each other.
While the place that cannabinoid receptors occupy in the field of pharmacology research is still evolving, strong evidence implicates their ability to regulate neuronal, vascular, and immune functions. An understanding of the expression, function, and regulation of these receptors, the molecular mechanism involved in the production and inactivation of their endogenous ligands, and how phytocannabinoids interfere with this signaling system is clearly important if we are rationally and comprehensively to assess the function of the cannabinoid signaling system in human health and disease.
Acknowledgements
This work was supported by the National Institute on Drug Abuse.
References
1. Watson SJ, Benson JA, Joy JE. Marijuana and medicine: assessing the science base. Arch Gen Psychiatry. 2000;57:547-552.
PubMed DOI: 10.1001/archpsyc.57.6.547
2. Iversen LL. The Science of Marijuana. Oxford, UK: Oxford University Press; 2000.
3. Gaoni Y, Mechoulam R. Isolation, structure and partial synthesis of an active constituent of hashish. J Am Chem Soc. 1964;86:1646-1647.
DOI: 10.1021/ja01062a046
4. Hall W, Solowij N. Adverse effects of cannabis. Lancet. 1998;352:1611-1616.
PubMed DOI: 10.1016/S0140-6736(98)05021-1
5. Malfait AM, Gallily R, Sumariwalla PF, et al. The nonpsychoactive cannabis constituent cannabidiol is an oral anti-arthritic therapeutic in murine collagen-induced arthritis. Proc Natl Acad Sci USA. 2000;97:9561-9566.
PubMed DOI: 10.1073/pnas.160105897
6. Herring AC, Kaminski NE. Cannabinol-mediated inhibition of nuclear factor-κB, cAMP response element-binding protein, and interleukin-2 secretion by activated thymocytes. J Pharmacol Exp Ther. 1999;291:1156-1163.
PubMed
7. Matsuda LA, Lolait SJ, Brownstein MJ, Young AC, Bonner TI. Structure of a cannabinoid receptor and functional expression of the cloned cDNA. Nature. 1990;346:561-564.
PubMed DOI: 10.1038/346561a0
8. Munro S, Thomas KL, Abu-Shaar M. Molecular characterization of a peripheral receptor for cannabinoids. Nature. 1993;365:61-65.
PubMed DOI: 10.1038/365061a0
9. Freund TF, Katona I, Piomelli D. Role of endogenous cannabinoids in synaptic signaling. Physiol Rev. 2003;83:1017-1066.
PubMed
10. Marsicano G, Goodenough S, Monory K, et al. CB1 cannabinoid receptors and on-demand defense against excitotoxicity. Science. 2003;302:84-88.
PubMed DOI: 10.1126/science.1088208
11. Rodríguez JJ, Mackie K, Pickel VM. Ultrastructural localization of the CB1 cannabinoid receptor in µ-opioid receptor patches of the rat caudate putamen nucleus. J Neurosci. 2001;21:823-833.
PubMed
12. Molina-Holgado E, Vela JM, Arévalo-Martin A, et al. Cannabinoids promote oligodendrocyte progenitor survival: involvement of cannabinoid receptor and phosphatidyllinositol-3 kinase/Akt signaling. J Neurosci. 2002;22:9742-9753.
PubMed
13. Aguado T, Monory K, Palazuelos J, et al. The endocannabinoid system drives neural progenitor proliferation. FASEB J. 2005;19:1704-1706.
PubMed
14. Felder CC, Veluz JS, Williams HL, Briley EM, Matsuda LA. Cannabinoid agonists stimulate both receptor- and non-receptor-mediated signal transduction pathways in cells transfected with and expressing the cannabinoid receptor clones. Mol Pharmacol. 1992;42:838-845.
PubMed
15. Glass M, Felder CC. Concurrent stimulation of cannabinoid CB1 and dopamine D2 receptors augments cAMP accumulation in striatal neurons: evidence for a Gs linkage to the CB1 receptor. J Neurosci. 1997;17:5327-5333.
PubMed
16. Huestis MA, Gorelick DA, Heishman SJ, et al. Blockade of effects of smoked marijuana by the CBl-selective cannabinoid receptor antagonist SR141716. Arch Gen Psychiatry. 2001;58:322-328.
PubMed DOI: 10.1001/archpsyc.58.4.322
17. Straiker A, Mackie K. Depolarization-induced suppression of excitation in murine autaptic hippocampal neurones. J Physiol. 2005;569:501-517.
PubMed DOI: 10.1113/jphysiol.2005.091918
18. Kelley BG, Thayer SA. Delta 9-tetrahydrocannabinol antagonizes endocannabinoid modulation of synaptic transmission between hippocampal neurons in culture. Neuropharmacology. 2004;46:709-715.
PubMed DOI: 10.1016/j.neuropharm.2003.11.005
19. Jordan JD, He JC, Eungdamrong NJ, et al. Cannabinoid receptor-induced neurite outgrowth is mediated by Rap1 activation through G(alpha)o/i-triggered proteasomal degradation of Rap1GAPII. J Biol Chem. 2005;280:11413-11421.
PubMed DOI: 10.1074/jbc.M411521200
20. Kim D, Thayer SA. Cannabinoids inhibit the formation of new synapses between hippocampal neurons in culture. J Neurosci. 2001;21:RC146.
PubMed
21. Jin K, Xie L, Kim SH, et al. Defective adult neurogenesis in CB1 cannabinoid receptor knockout mice. Mol Pharmacol. 2004;66:204-208.
PubMed DOI: 10.1124/mol.66.2.204
22. Galiègue S, Mary S, Marchand J, et al. Expression of central and peripheral cannabinoid receptors in human immune tissues and leukocyte subpopulations. Eur J Biochem. 1995;232:54-61.
PubMed DOI: 10.1111/j.1432-1033.1995.tb20780.x
23. Patrini G, Sacerdote P, Fuzio D, Manfredi B, Parolaro D. Regulation of immune functions in rat splenocytes after acute and chronic in vivo treatment with CP-55,940, a synthetic cannabinoid compound. J Neuroimmunol. 1997;80:143-148.
PubMed DOI: 10.1016/S0165-5728(97)00149-5
24. Richardson JD, Kilo S, Hargreaves KM. Cannabinoids reduce hyperalgesia and inflammation via interaction with peripheral CB1 receptors. Pain. 1998;75:111-119.
PubMed DOI: 10.1016/S0304-3959(97)00213-3
25. Massi P, Fuzio D, Viganò D, Sacerdote P, Parolaro D. Relative involvement of cannabinoid CB1 and CB2 receptors in the ∆9-tetrahydrocannabinol-induced inhibition of natural killer activity. Eur J Pharmacol. 2000;387:343-347.
PubMed DOI: 10.1016/S0014-2999(99)00860-2
26. Buckley NE, McCoy KL, Mezey E, et al. Immunomodulation by cannabinoids is absent in mice deficient for the cannabinoid CB(2) receptor. Eur J Pharmacol. 2000;396:141-149.
PubMed DOI: 10.1016/S0014-2999(00)00211-9
27. Felder CC, Joyce KE, Briley EM, et al. Comparison of the pharmacology and signal transduction of the human cannabinoid CB1 and CB2 receptors. Mol Pharmacol. 1995;48:443-450.
PubMed
28. Hanus L, Breuer A, Tchilibon S, et al. HU-308: a specific agonist for CB2, a peripheral cannabinoid receptor. Proc Natl Acad Sci USA. 1999;96:14228-14233.
PubMed DOI: 10.1073/pnas.96.25.14228
29. Conti S, Costa B, Colleoni M, Parolaro D, Giagnoni G. Antiinflammatory action of endocannabinoid palmitoylethanolamide and the synthetic cannabinoid nabilone in a model of acute inflammation in the rat. Br J Pharmacol. 2002;135:181-187.
PubMed
30. McCoy KL, Gainey D, Cabral GA. ∆9-tetrahydrocannabinol modulates antigen processing by macrophages. J Pharmacol Exp Ther. 1995;273:1216-1223.
PubMed
31. McCoy KL, Matveyeva M, Carlisle SJ, Cabral GA. Cannabinoid inhibition of the processing of intact lysozyme by macrophages: evidence for CB2 receptor participation. J Pharmacol Exp Ther. 1999;289:1620-1625.
PubMed
32. McKallip RJ, Lombard C, Martin BR, Nagarkatti M, Nagarkatti PS. Delta(9)-tetrahydrocannabinol-induced apoptosis in the thymus and spleen as a mechanism of immunosuppression in vitro and in vivo. J Pharmacol Exp Ther. 2002;302:451-465.
PubMed DOI: 10.1124/jpet.102.033506
33. Derocq J-M, Ségui M, Marchand J, Le Fur G, Casellas P. Cannabinoids enhance human B-cell growth at low nanomolar concentrations. FEBS Lett. 1995;369:177-182.
PubMed DOI: 10.1016/0014-5793(95)00746-V
34. Schatz AR, Lee M, Condie RB, Pulaski JT, Kaminski NE. Cannabinoid receptors CB1 and CB2: a characterization of expression and adenylate cyclase modulation within the immune system. Toxicol Appl Pharmacol. 1997;142:278-287.
PubMed DOI: 10.1006/taap.1996.8034
35. Sugiura T, Kondo S, Kishimoto S, et al. Evidence that 2-arachidonylglycerol but not N-palmitpylethanolamine or anandamide is the physiological ligand for the cannabinoid CB2 receptor: comparison of the agonistic activities of various cannabinoid receptor ligands in HL-60 cells. J Biol Chem. 2000;275:605-612.
PubMed DOI: 10.1074/jbc.275.1.605
36. Carlisle SJ, Marciano-Cabral F, Staab A, Ludwick C, Cabral GA. Differential expression of the CB2 cannabinoid receptor by rodent macrophages and macrophage-like cells in relation to cell activation. Int Immunopharmacol. 2002;2:69-82.
PubMed DOI: 10.1016/S1567-5769(01)00147-3
37. Van Sickle MD, Duncan M, Kingsley PJ, et al. Identification and functional characterization of brainstem cannabinoid CB2 receptors. Science. 2005;310:329-332.
PubMed DOI: 10.1126/science.1115740
38. Maresz K, Carrier EJ, Ponomarev ED, Hillard CJ, Dittel BN. Modulation of the cannabinoid CB2 receptor in microglial cells in response to inflammatory stimuli. J Neurochem. 2005;95:437-445.
PubMed DOI: 10.1111/j.1471-4159.2005.03380.x
39. Benito C, Núnez E, Tolón RM, et al. Cannabinoid CB2 receptors and fatty acid amide hydrolase are selectively overexpressed in neuritic plaques-associated glia in Alzheimer's disease brains. J Neurosci. 2003;23:11136-11141.
PubMed
40. Walter L, Franklin A, Witting A, et al. Non-psychotropic cannabinoid receptors regulate microglial cell migration. J Neurosci. 2003;23:1398-1405.
PubMed
41. Kishimoto S, Gokoh M, Oka S, et al. 2-Arachidonoylglycerol induces the migration of HL-60 cells differentiated into macrophage-like cells and human peripheral blood monocytes through the cannabinoid CB2 receptor-dependent mechanism. J Biol Chem. 2003;278:24469-24475.
PubMed DOI: 10.1074/jbc.M301359200
42. Jordà MA, Verbakel SE, Valk PJ, et al. Hematopoietic cells expressing the peripheral cannabinoid receptor migrate in response to the endocannabinoid 2-arachidonoylglycerol. Blood. 2002;99:2786-2793.
PubMed DOI: 10.1182/blood.V99.8.2786
43. Gokoh M, Kishimoto S, Oka S, et al. 2-Arachidonoylglycerol, an endogenous cannabinoid receptor ligand, induces rapid actin polymerization in HL-60 cells differentiated into macrophage-like cells. Biochem J. 2005;386:583-589.
PubMed DOI: 10.1042/BJ20041163
44. Waksman Y, Olson JM, Carlisle SJ, Cabral GA. The central cannabinoid receptor (CB1) mediates inhibition of nitric oxide production by rat microglial cells. J Pharmacol Exp Ther. 1999;288:1357-1366.
PubMed
45. Klegeris A, Bissonnette CJ, McGeer PL. Reduction of human monocytic cell neurotoxicity and cytokine secretion by ligands of the cannabinoid-type CB2 receptor. Br J Pharmacol. 2003;139:775-786.
PubMed DOI: 10.1038/sj.bjp.0705304
46. Facchinetti F, Del Giudice E, Furegato S, Passarotto M, Leon A. Cannabinoids ablate release of TNFα in rat microglial cells stimulated with lypopolysaccharide. Glia. 2003;41:161-168.
PubMed DOI: 10.1002/glia.10177
47. Carrier EJ, Kearn CS, Barkmeier AJ, et al. Cultured rat microglial cells synthesize the endocannabinoid 2-arachidonylglycerol, which increases proliferation via a CB2 receptor-dependent mechanism. Mol Pharmacol. 2004;65:999-1007.
PubMed DOI: 10.1124/mol.65.4.999
48. Derocq J-M, Jbilo O, Bouaboula M, Ségui M, Clère C, Casellas P. Genomic and functional changes induced by the activation of the peripheral cannabinoid receptor CB2 in the promyelocytic cells HL-60: possible involvement of the CB2 receptor in cell differentiation. J Biol Chem. 2000;275:15621-15628.
PubMed DOI: 10.1074/jbc.275.21.15621
49. Devane WA, Hanus L, Breuer A, et al. Isolation and structure of a brain constituent that binds to the cannabinoid receptor. Science. 1992;258:1946-1949.
PubMed
50. Di Marzo V, Fontana A, Cadas H, et al. Formation and inactivation of endogenous cannabinoid anandamide in central neurons. Nature. 1994;372:686-691.
PubMed DOI: 10.1038/372686a0
51. Giuffrida A, Parsons LH, Kerr TM, Rodríguez de Fonseca F, Navarro M, Piomelli D. Dopamine activation of endogenous cannabinoid signaling in dorsal striatum. Nat Neurosci. 1999;2:358-363.
PubMed DOI: 10.1038/7268
52. Walker JM, Huang SM, Strangman NM, Tsou K, Sañudo-Peña MC. Pain modulation by release of the endogenous cannabinoid anandamide. Proc Natl Acad Sci USA. 1999;96:12198-12203.
PubMed DOI: 10.1073/pnas.96.21.12198
53. Di Marzo V, De Petrocellis L, Sugiura T, Waku K. Potential biosynthetic connections between the 2 cannabimimetic eicosanoids, anandamide and 2-arachidonoyl-glycerol, in mouse neuroblastoma cells. Biochem Biophys Res Commun. 1996;227:281-288.
PubMed DOI: 10.1006/bbrc.1996.1501
54. Cadas H, Schinelli S, Piomelli D. Membrane localization of N-acylphosphatidylethanolamine in central neurons: studies with exogenous phospholipases. J Lipid Mediat Cell Signal. 1996;14:63-70.
PubMed DOI: 10.1016/0929-7855(96)00510-X
55. Sugiura T, Kondo S, Sukagawa A, et al. Transacylase-mediated and phosphodiesterase-mediated synthesis of N-arachidonoylethanolamine, an endogenous cannabinoid-receptor ligand, in rat brain microsomes: comparison with synthesis from free arachidonic acid and ehtanolamine Eur J Biochem. 1996;240:53-62.
PubMed
56. Okamoto Y, Morishita J, Tsuboi K, Tonai T, Ueda N. Molecular characterization of a phospholipase D generating anandamide and its congeners. J Biol Chem. 2004;279:5298-5305.
PubMed DOI: 10.1074/jbc.M306642200
57. Piomelli D. The challenge of brain lipidomics. Prostaglandins Other Lipid Mediat. 2005;77:23-34.
PubMed DOI: 10.1016/j.prostaglandins.2004.09.006
58. Calignano A, La Rana G, Giuffrida A, Piomelli D. Control of pain initiation by endogenous cannabinoids. Nature. 1998;394:277-281.
PubMed DOI: 10.1038/28393
59. Felder CC, Nielsen A, Briley EM, et al. Isolation and measurement of the endogenous cannabinoid receptor agonist, anandamide, in brain and peripheral tissues of human and rat. FEBS Lett. 1996;393:231-235.
PubMed DOI: 10.1016/0014-5793(96)00891-5
60. Schmid PC, Kuwae T, Krebsbach RJ, Schmid HHO. Anandamide and other N-acylethanolamines in mouse peritoneal macrophages. Chem Phys Lipids. 1997;87:103-110.
PubMed DOI: 10.1016/S0009-3084(97)00032-7
61. Schmid PC, Paria BC, Krebsbach RJ, Schmid HHO, Dey SK. Changes in anandamide levels in mouse uterus are associated with uterine receptivity for embryo implantation. Proc Natl Acad Sci USA. 1997;94:4188-4192.
PubMed DOI: 10.1073/pnas.94.8.4188
62. Calignano A, Kátona I, Désarnaud F, et al. Bidirectional control of airway responsiveness by endogenous cannabinoids. Nature. 2000;408:96-101.
PubMed DOI: 10.1038/35040576
63. Mackie K, Devane WA, Hille B. Anandamide, an endogenous cannabinoid, inhibits calcium currents as a partial agonist in N18 neuroblastoma cells. Mol Pharmacol. 1993;44:498-503.
PubMed
64. Fride E, Mechoulam R. Pharmacological activity of the cannabinoid receptor agonist, anandamide, a brain constituent. Eur J Pharmacol. 1993;231:313-314.
PubMed DOI: 10.1016/0014-2999(93)90468-W
65. Cravatt BF, Demarest K, Patricelli MP, et al. Supersensitivity to anandamide and enhanced endogenous cannabinoid signaling in mice lacking fatty acid amide hydrolase. Proc Natl Acad Sci USA. 2001;98:9371-9376.
PubMed DOI: 10.1073/pnas.161191698
66. Griffin G, Tao Q, Abood ME. Cloning and pharmacological characterization of the rat CB2 cannabinoid receptor. J Pharmacol Exp Ther. 2000;292:886-894.
PubMed
67. Gonsiorek W, Lunn C, Fan X, Narula S, Lundell D, Hipkin RW. Endocannabinoid 2-arachidonyl glycerol is a full agonist through human type 2 cannabinoid receptor: antagonism by anandamide. Mol Pharmacol. 2000;57:1045-1050.
PubMed
68. Kathuria S, Gaetani S, Fegley D, et al. Modulation of anxiety through blockade of anandamide hydrolysis. Nat Med. 2003;9:76-81.
PubMed DOI: 10.1038/nm803
69. Hampson AJ, Hill WAG, Zan-Phillips M, et al. Anandamide hydroxylation by brain lipoxygenase: metabolite structures and potencies at the cannabinoid receptor. Biochim Biophys Acta. 1995;1259:173-179.
PubMed
70. Yu M, Ives D, Ramesha CS. Synthesis of prostaglandin E2 ethanolamide from anandamide by cyclooxygenase-2. J Biol Chem. 1997;272:21181-21186.
PubMed DOI: 10.1074/jbc.272.34.21181
71. Weber A, Ni J, Ling KH, et al. Formation of prostamides from anandamide in FAAH knockout mice analyzed by HPLC with tandem mass spectrometry. J Lipid Res. 2004;45:757-763.
PubMed DOI: 10.1194/jlr.M300475-JLR200
72. Kim J, Alger BE. Inhibition of cyclooxygenase-2 potentiates retrograde endocannabinoid effects in hippocampus. Nat Neurosci. 2004;7:697-698.
PubMed DOI: 10.1038/nn1262
73. Mechoulam R, Ben-Shabat S, Hanus L, et al. Identification of an endogenous 2-monoglyceride, present in canine gut, that binds to cannabinoid receptors. Biochem Pharmacol. 1995;50:83-90.
PubMed DOI: 10.1016/0006-2952(95)00109-D
74. Sugiura T, Kondo S, Sukagawa A, et al. 2-arachidonoylglycerol: a possible endogenous cannabinoid receptor ligand in brain. Biochem Biophys Res Commun. 1995;215:89-97.
PubMed DOI: 10.1006/bbrc.1995.2437
75. Stella N, Schweitzer P, Piomelli D. A second endogenous cannabinoid that modulates long-term potentiation. Nature. 1997;388:773-778.
PubMed DOI: 10.1038/42015
76. Prescott SM, Majerus PW. Characterization of 1,2-diacylglycerol hydrolysis in human platelets: demonstration of an arachidonoyl-monoacylglycerol intermediate. J Biol Chem. 1983;258:764-769.
PubMed
77. Farooqui AA, Taylor AW, Horrocks LA. Separation of bovine brain mono- and diacylglycerol lipases by heparin sepharose affinity chromatography. Biochem Biophys Res Commun. 1984;122:1241-1246.
PubMed DOI: 10.1016/0006-291X(84)91225-7
78. Maejima T, Oka S, Hashimotodani Y, et al. Synaptically driven endocannabinoid release requires Ca2+-assisted metabotropic glutamate receptor subtype 1 to phospholipase Cbeta4 signaling cascade in the cerebellum. J Neurosci. 2005;25:6826-6835.
PubMed DOI: 10.1523/JNEUROSCI.0945-05.2005
79. Hashimotodani Y, Ohno-Shosaku T, Tsubokawa H, et al. Phospholipase Cbeta serves as a coincidence detector through its Ca2+ dependency for triggering retrograde endocannabinoid signal. Neuron. 2005;45:257-268.
PubMed DOI: 10.1016/j.neuron.2005.01.004
80. Bisogno T, Howell F, Williams G, et al. Cloning of the first sn1-DAG lipases points to the spatial and temporal regulation of endocannabinoid signaling in the brain. J Cell Biol. 2003;163:463-468.
PubMed DOI: 10.1083/jcb.200305129
81. Bisogno T, Sepe N, Melck D, Maurelli S, De Petrocellis L, Di Marzo V. Biosynthesis, release and degradation of the novel endogenous cannabimimetic metabolite 2-arachidonoylglycerol in mouse neuroblastoma cells. Biochem J. 1997;322:671-677.
PubMed
82. Bisogno T, Maccarrone M, De Petrocellis L, et al. The uptake by cells of 2-arachidonoylglycerol, an endogenous agonist of cannabinoid receptors. Eur J Biochem. 2001;268:1982-1989.
PubMed DOI: 10.1046/j.1432-1327.2001.02072.x
83. Beltramo M, Piomelli D. Carrier-mediated transport and enzymatic hydrolysis of the endogenous cannabinoid 2-arachidonylglycerol. Neuroreport. 2000;11:1231-1235.
PubMed
84. Dinh TP, Carpenter D, Leslie FM, et al. Brain monoglyceride lipase participating in endocannabinoid inactivation. Proc Natl Acad Sci USA. 2002;99:10819-10824.
PubMed DOI: 10.1073/pnas.152334899
85. Dinh TP, Kathuria S, Piomelli D. RNA interference suggests a primary role for monoacylglycerol lipase in the degradation of the endocannabinoid 2-arachidonoylglycerol. Mol Pharmacol. 2004;66:1260-1264.
PubMed DOI: 10.1124/mol.104.002071
86. Kozak KR, Rowlinson SW, Marnett LJ. Oxygenation of the endocannabinoid, 2-arachidonylglycerol, to glyceryl prostaglandins by cyclooxygenase-2. J Biol Chem. 2000;275:33744-33749.
PubMed DOI: 10.1074/jbc.M007088200
87. Goparaju SK, Ueda N, Yamaguchi H, Yamamoto S. Anandamide amidohydrolase reacting with 2-arachidonoylglycerol, another cannabinoid receptor ligand. FEBS Lett. 1998;422:69-73.
PubMed DOI: 10.1016/S0014-5793(97)01603-7
88. Breivogel CS, Griffin G, Di Marzo V, Martin BR. Evidence for a new G protein-coupled cannabinoid receptor in mouse brain. Mol Pharmacol. 2001;60:155-163.
PubMed
89. Di Marzo V, Breivogel CS, Tao Q, et al. Levels, metabolism, and pharmacological activity of anandamide in CB1 cannabinoid receptor knockout mice: evidence for non-CB1, non-CB2 receptor-mediated actions of anandamide in mouse brain. J Neurochem. 2000;75:2434-2444.
PubMed DOI: 10.1046/j.1471-4159.2000.0752434.x
90. Hájos N, Ledent C, Freund TF. Novel cannabinoid-sensitive receptor mediates inhibition of glutamatergic synaptic transmission in the hippocampus. Neuroscience. 2001;106:1-4.
PubMed DOI: 10.1016/S0306-4522(01)00287-1
91. Hájos N, Freund TF. Pharmacological separation of cannabinoid sensitive receptors on hippocampal excitatory and inhibitory fibers. Neuropharmacology. 2002;43:503-510.
PubMed DOI: 10.1016/S0028-3908(02)00157-0
92. Hoffman AF, Macgill AM, Smith D, Oz M, Lupica CR. Species and strain differences in the expression of a novel glutamate-modulating cannabinoid receptor in the rodent hippocampus. Eur J Neurosci. 2005;22:2387-2391.
PubMed DOI: 10.1111/j.1460-9568.2005.04401.x
93. Rouach N, Nicoll RA. Endocannabinoids contribute to short-term but not long-term mGluR-induced depression in the hippocampus. Eur J Neurosci. 2003;18:1017-1020.
PubMed DOI: 10.1046/j.1460-9568.2003.02823.x
94. Pistis M, Perra S, Pillolla G, Melis M, Gessa GL, Muntoni AL. Cannabinoids modulate neuronal firing in the rat basolateral amygdala: evidence for CB1- and non-CB1-mediated actions. Neuropharmacology. 2004;46:115-125.
PubMed DOI: 10.1016/j.neuropharm.2003.08.003
95. Houser SJ, Eads M, Embrey JP, Welch SP. Dynorphin B and spinal analgesia: induction of antinociception by the cannabinoids CP55,940, Delta(9)-THC and anandamide. Brain Res. 2000;857:337-342.
PubMed DOI: 10.1016/S0006-8993(00)01981-8
96. Welch SP, Huffman JW, Lowe J. Differential blockade of the antinociceptive effects of centrally administered cannabinoids by SR141716A. J Pharmacol Exp Ther. 1998;286:1301-1308.
PubMed
97. Begg M, Pacher P, Batkai S, et al. Evidence for novel cannabinoid receptors. Pharmacol Ther. 2005;106:133-145.
PubMed DOI: 10.1016/j.pharmthera.2004.11.005
98. Járai Z, Wagner JA, Varga K, et al. Cannabinoid-induced mesenteric vasodilation through an endothelial site distinct from CB1 or CB2 receptors. Proc Natl Acad Sci USA. 1999;96:14136-14141.
PubMed DOI: 10.1073/pnas.96.24.14136
99. Offertáler L, Mo F, Bátkai S, et al. Selective ligands and cellular effectors of a G protein-coupled endothelial cannabinoid receptor. Mol Pharmacol. 2003;63:699-705.
PubMed DOI: 10.1124/mol.63.3.699
100. Begg M, Mo F-M, Offertáler L, et al. G protein-coupled endothelial receptor for atypical cannabinoid ligands modulates a Ca2+-dependent K+ current. J Biol Chem. 2003;278:46188-46194.
PubMed DOI: 10.1074/jbc.M307258200
101. Bouaboula M, Rinaldi M, Carayon P, et al. Cannabinoid-receptor expression in human leukocytes. Eur J Biochem. 1993;214:173-180.
PubMed DOI: 10.1111/j.1432-1033.1993.tb17910.x
102. Klein TW, Newton C, Larsen K, et al. The cannabinoid system and immune modulation. J Leukoc Biol. 2003;74:486-496.
PubMed DOI: 10.1189/jlb.0303101
103. Walter L, Stella N. Cannabinoids and neuroinflammation. Br J Pharmacol. 2004;141:775-785.
PubMed DOI: 10.1038/sj.bjp.0705667
104. Lambert DM, Vandevoorde S, Jonsson K-O, Fowler CJ. The palmitoylethanolamide family: a new class of anti-inflammatory agents? Curr Med Chem. 2002;9:663-674.
PubMed
105. Jaggar SI, Hasnie FS, Sellaturay S, Rice AS. The anti-hyperalgesic actions of the cannabinoid anandamide and the putative CB2 receptor agonist palmitoylethanolamide in visceral and somatic inflammatory pain. Pain. 1998;76:189-199.
PubMed DOI: 10.1016/S0304-3959(98)00041-4
106. Cadas H, di Tomaso E, Piomelli D. Occurrence and biosynthesis of endogenous cannabinoid precursor, N-arachidonoyl phosphatidylethanolamine, in rat brain. J Neurosci. 1997;17:1226-1242.
PubMed
107. Hansen HS, Lauritzen L, Strand AM, Vinggaard AM, Frandsen A, Schousboe A. Characterization of glutamate-induced formation of N-acylphosphatidylethanolamine and N-acylethanolamine in cultured neocortical neurons. J Neurochem. 1997;69:753-761.
PubMed
108. Stella N, Piomelli D. Receptor-dependent formation of endogenous cannabinoids in cortical neurons. Eur J Pharmacol. 2001;425:189-196.
PubMed DOI: 10.1016/S0014-2999(01)01182-7
109. Walter L, Franklin A, Witting A, Möller T, Stella N. Astrocytes in culture produce anandamide and other acylethanolamides. J Biol Chem. 2002;277:20869-20876.
PubMed DOI: 10.1074/jbc.M110813200
110. Walter L, Stella L. Endothelin-1 increases 2-arachidonyl glycerol (2-AG) production in astrocytes. Glia. 2003;44:85-90.
PubMed DOI: 10.1002/glia.10270
111. Franklin A, Parmentier-Batteur S, Walter L, Greenberg DA, Stella N. Palmitoylethanolamide increases after focal cerebral ischemia and potentiates microglial cells motility. J Neurosci. 2003;23:7767-7775.
PubMed
112. Ueda N, Yamanaka K, Yamamoto S. Purification and characterization of an acid amidase selective for N-palmitoylethanolamine, a putative endogenous anti-inflammatory substance. J Biol Chem. 2001;276:35552-35557.
PubMed DOI: 10.1074/jbc.M106261200
113. Tsuboi K, Sun YX, Okamoto Y, Araki N, Tonai T, Ueda N. Molecular characterization of N-acylethanolamine-hydrolyzing acid amidase, a novel member of the choloylglycine hydrolase family with structural and functional similarity to acid ceramidase. J Biol Chem. 2005;280:11082-11092.
PubMed DOI: 10.1074/jbc.M413473200
114. Ueda N, Tsuboi K, Lambert DM. A second N-acylethanolamine hydrolase in mammalian tissues. Neuropharmacology. 2005;48:1079-1085.
PubMed DOI: 10.1016/j.neuropharm.2004.12.017
115. Sun YX, Tsuboi K, Zhao LY, Okamoto Y, Lambert DM, Ueda N. Involvement of N-acylethanolamine-hydrolyzing acid amidase in the degradation of anandamide and other N-acylethanolamines in macrophages. Biochim Biophys Acta. 2005;1736:211-220.
PubMed
116. Gulyas AI, Cravatt BF, Bracey MH, et al. Segregation of 2 endocannabinoid-hydrolyzing enzymes into pre- and postsynaptic compartments in the rat hippocampus, cerebellum and amygdala. Eur J Neurosci. 2004;20:441-458.
PubMed DOI: 10.1111/j.1460-9568.2004.03428.x
117. Sawzdargo M, Nguyen T, Lee DK, et al. Identification and cloning of three novel human G protein-coupled receptor genes GPR52, PsiGPR53 and GPR55: GPR55 is extensively expressed in human brain. Brain Res Mol Brain Res. 1999;64:193-198.
PubMed DOI: 10.1016/S0169-328X(98)00277-0
118. Brown A, Wise A, inventors. GlaxoSmithKline, assignee. Identification of modulators of GPR55 activity. US patent 0 113 814. June 19, 2003.
119. Drmota T, Greasley P, Groblewski T, inventors. AstraZeneca, assignee. Screening assays for cannabinoid-ligand-type modulators of GPR55. WIPO patent 074 844. September 2, 2004.
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brainthor said:How old is the human race?
Author: 29561 CategoryDiscussion) Created
Humans are currently thought to have emerged between 1 and 2 million years ago, but recent findings may prove that man is much older then that.
What may be the oldest fossil footprint yet found was discovered in June of 1968 by William J. Meister, an amateur fossil collector. This print is estimated to be around 300 to 600 MILLION years old! A sandaled shoe crushing a trilobite; is this proof that there were previous civilizations on earth, or visitors from another world? Could this foot print be from God? The sandal that crushed a living trilobite was 10 1/2 inches long and 3 1/2 inches wide; the heel is indented slightly more than the sole, as a human shoe print would be.
I have to comment on this, The so called foot prints are forgotten and no one in the pal comunity is beliving it,
The oldest belived or accepted (taxonomical) hominina is around 7 million years old, but the primates goes as far back, around 60 million.
G
Guest
going a little off topic and mind absorbing crazy..life is good
The Genesis Chronicles: A Proposed History Of The Morning Of The World
Chapter 4: EVOLUTION AND THE FOSSIL RECORD
This chapter covers the following topics:
What We Should Find
How Are Fossils Made?
The Geologic Table
The Pitfalls of Radioactive Dating
Back to the Beginning
The Fish That Walked
The Terrible Lizards
A Feathered Flying Machine
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What We Should Find
Now we have reached the area where evolution feels strongest--the fossil record. Fossils are the scientist's books on the earth's past; if there is proof that evolution happened, this is where it will be found. If the earth is really billions of years old, and every life form of today has evolved from something else, then we should find countless examples of fossils representing plants and animals that are not quite one thing, not quite another. The impression that this is true is so strong that when confronted with the idea that evolution might not be true, the ordinary person is likely to ask, "Then where did all those fossils come from?" Some Christians inclined to believe in creation even wonder if dinosaurs really existed; they think the fossil record is a complete but bogus testimony, some kind of satanic plot.
But is the fossil record really complete? When Darwin wrote The Origin of Species paleontology was a new science, only a few decades old, so we had studied only a few fossils to that point. Darwin did not have a single fossil to prove his theory--he admitted he did not have any--but he was optimistic that eventually they would turn up. It has been nearly a century and a half since then, and in our museums we have fossils representing over a quarter of a million extinct species. If evolution is correct, than the laws of probability tell us that many of those fossils will represent transitional life forms, creatures in the process of evolving from one species to another. It should be possible to go to a great natural history museum like those in Chicago, New York or Washington, D.C., and see transitional fossils all over the place. On the other hand, if our view of creation is accurate, then you will find in the fossil record evidence of life forms coming into existence fully developed, without ages of development preceding each one. According to creationism, we will find fossils from previous ages, but trees will always be trees, insects will always be insects, fish will always be fish, lizards will always be lizards, monkeys will always be monkeys, and people will always be people.
How Are Fossils Made?
To begin with, we must look at the way in which fossils are made. Typically, an animal or plant dies and is quickly buried before scavengers and decay can get to it. Then pressure turns the surrounding sand or soil into rock. After that water seeps in, and bit by bit, it dissolves part of the organism. Every time it does so it replaces the molecules it removes with molecules from the surrounding rock. At last none of the original organism is left. There is a copy of it made out of stone instead.
We call this process petrification, and it can happen in just a few years under the right circumstances. When on speaking tours, Dr. Ken Ham likes to show a picture of a floppy beach hat somebody left in an Australian mine in the 1930s, to be found 50 years later; it was a soft hat originally, but it's a hard hat now! For uniformitarianism, and thus evolution, to be valid, there must be places around today where fossils are being formed regularly, by natural processes which geologists can identify. Can anybody name such a place? I have never heard of one, despite two centuries of digging and searching in the rock beneath our feet.
Let us consider, for example, the requirement that the organism has to be immediately buried. Suppose one day you brought home a cow, put it in the backyard and shot it (Don't do this in the driveway or the neighbors will complain!). Then over the next eleven weeks you went out from time to time, studied the carcass and took notes. How long do you think it would take to become a fossil? It probably won't become a fossil at all. On the Great Plains in the late nineteenth century there was death on a massive scale, when hunters shot buffalo by the millions, but because the conditions for fossil formation were not there, nobody has found one fossil buffalo dating back to the days when the prairie was the white man's "happy hunting grounds."
Now let's consider the origin of the most common vertebrate fossils, those of fish. Immanuel Velikovsky had this to say about the subject:
"When a fish dies its body floats on the surface or sinks to the bottom and is devoured rather quickly, actually in a matter of hours, by other fish. However, the fossil fish found in sedimentary rock is very often preserved with all of its bones intact. Entire shoals of fish over large areas, numbering billions of specimens, are found in a state of agony, but with no mark of a scavenger's attack.
"The explanation of the origin of fossils by uniformity and evolution contradicts the fundamental principle of these theories: Nothing took place in the past that does not take place in the present. Today no fossils are formed."(1) [Italics are mine, C.K.]
Geologist Harold G. Coffin, of the Geoscience Research Institute in Berrien Springs, MI, wrote about an experiment in the formation of fish fossils conducted by two scientists named Zangerl and Richardson. Here are the results:
"In attempting to evaluate the rate of fossilization in the Pennsylvania black shales of Indiana, they placed dead fish in the protecting wire cages and dropped them into the black muds at the bottom of several Louisiana lagoons or bayous. These black muds are thought to resemble the sediments from which the dark shales were derived. To the great surprise of the investigators, fish weighing from one-half to three-fourths of a pound were found to have all the soft parts reduced and all the bones completely disarticulated in six and one-half days! Decomposition to the state of total disarticulation apparently occurs at great speed, perhaps in less time than indicated above, since none were checked before six and one-half days. Delicate fossil fish showing every minute ray and bone in position are common and must represent a burial by oxygen- and bacteria-excluding sediments within hours of death if this experiment is a valid indication."(2)
That ought to show us that you can't get fish fossils by dumping cyanide into an aquarium! The process which fossilizes fish is very uncommon, if it is taking place anywhere today, but fish fossils are not rare. It is estimated that eight hundred billion fish fossils are contained in the Karoo rock formation of South Africa. Geologist Hugh Miller tells us that the fish-containing Devonian rocks of England are full of fish that died violently, in an area that covers more than ten thousand square miles. Closer to home, Harry S. Ladd of the US Geological Survey says that "more than a billion fish, averaging six to eight inches in length, died on four square miles of bay bottom."(3) And rocks containing sea fossils (fossils of fish and shells) are found over more than 75% of the earth, even on the slopes of Mt. Everest. Catastrophists have long known that only a worldwide disaster involving water, namely Noah's Flood, could have produced death on such a large scale.
Even more amazing is the recent announcement of the discovery of a tyrannosaurus rex skeleton whose bones contained soft tissue. In a broken thighbone, between the expected hard minerals, they found "blood vessels--still flexible and elastic after 68 million years--and apparently intact cells."(4) It is nearly impossible to preserve soft tissues for a few thousand years (usually subzero temperatures and an extremely low humidity are required), so as we go to the press, evolutionists are rushing to explain how soft tissues can last for 68 million years.
Another place where faulty reasoning is used to explain fossil formation is in the world's vast coal deposits. Since coal is by nature a "fossil fuel," we have discovered many fascinating plants and animals in coal mines, including a number of dinosaurs. Rene Noorbergen reports that in the Geisental lignite deposits of Germany, leaves have been so well preserved that they still are green with chlorophyll; there are also beautifully colored tropical beetles with the soft parts of their body, including the contents of their intestines, preserved intact. Under normal conditions such materials decay or lose their color within a few hours of death, meaning that their burial in an anaerobic medium had to be done right away.(5)
Dr. Coffin points out some interesting facts about how coal is made:
"The thickness of peat needed to produce one foot of coal depends on a number of factors, such as the type of peat, the amount of water in the vegetable matter, and the type of coal. The scientific literature on coal gives figures ranging from a few feet to as many as twenty. Let us assume that ten feet would be near the average figure. On this basis, a coal seam thirty feet thick would require the compression of 300 feet of peat. A 400-foot seam of coal would be the result of a fantastic 4,000 feet of peat.
"There are few peat bogs, marshes, or swamps anywhere in the world today that reach 100 feet. Most of them are less than 50 feet. A much more reasonable alternative theory is that the vegetable matter has been concentrated and collected into an area by some force, undoubtedly water. . . .
"The concept of a global deluge that eroded out the forests and plant cover of the pre-Flood world, collected it in great mats of drifting debris, and eventually dropped it on the emerging land or on the sea bottom is the most reasonable answer to this problem of the great extent and uniform thickness of coal beds."(6)
Another problem overlooked is that often whole fossilized trees are found in coal, stretching through several layers of it. Since uniformitarianism tells us that no more than a few inches of peat are produced per year, by such reasoning some of these trees would have to stand for thousands of years before they were completely buried. Look around you; do you see any dead trees that have been standing for more than a few years? I know in my neighborhood that woodpeckers, termites and carpenter ants will bring down a dead tree in only a year or two, so how could so many trees have lasted long enough to be buried? Again we have a situation in the rocks that only makes sense if a sudden catastrophe involving rapid burial is the cause. Some of those trees are buried upside down; they certainly didn't grow that way!
The Geologic Table
As I pointed out in Chapter 1, the geologic scale of the earth's history found in most science books was drawn up by Charles Lyell before the theory of evolution was developed. A few changes have been made since then (as recently as the 1940s they thought that the world could not be more than two billion years old) but essentially geologists and paleontologists are using the same chart today. It generally looks like this:
The Geologic Table Era Period Major Life Forms How Long Ago (millions of years)
CENOZOIC Quaternary The weirdest creature of all 1 to now
Tertiary The age of mammals 63 to 1
MESOZOIC Cretaceous T. Rex & the flowers 135 to 63
Jurassic Birdy & Bronty 180 to 135
Triassic Tiny mammals & dinosaurs 225 to 180
PALEOZOIC Permian Weird reptiles 280 to 225
Carboniferous The creation of coal 345 to 280
Devonian Fish & forest 405 to 345
Silurian Life's a beach 425 to 405
Ordovician Go fishin' 500 to 425
Cambrian Hard bodies 600 to 500
PRE-CAMBRIAN ??? Before 600
Note: The Cenozoic Era is often divided into seven shorter periods called epochs, rather than just two periods. From oldest to youngest, the names of those epochs are Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene (Recent).
Now when they classify new fossils, scientists immediately go to this chart to find out what time frame to place them in. How do they do that? Do they use a sophisticated technique like radiocarbon dating? No, more often they look for an "index fossil" in the same rock. They have long believed that rocks found in two different places which contain the same fossils must be the same age. Because of this, a rock containing a trilobite or brachiopod is expected to come from the Cambrian period, and rocks with dinosaur bones in them are automatically dated to the Mesozoic era. This has led to some circular reasoning, meaning that we can trust none of the dates assigned to rocks. For example:
You: "How old is this fish fossil?"
Paleontologist: "40 million years old."
You: "How do you know that?"
Paleontologist: "Because it is in a rock that is 40 million years old."
Then you go to a geologist with the fossil and ask: "How old is this rock?"
Geologist: "40 million years old."
You: "Did you use potassium-Argon dating to find that out?"
Geologist: "No."
You: "Then how do you know it is 40 million years old?"
Geologist: "Because it has a 40-million-year-old fossil in it."
This means that the whole geologic table is based not so much on careful research as on it is on shaky assumptions that could collapse when exposed to enough evidence favoring a young, created Earth. I believe that such evidence does exist, but that most people have not opened their eyes to the truth. Duane Gish wrote a whole book on the subject in 1973 entitled Evolution: The Fossils Say No!, and nowadays you may find a larger, more up-to-date version with the title Evolution: The Challenge of the Fossil Record.(7)
One such problem is that the only place where a complete geologic table like the one shown can be found is in the textbooks. There is no place in the real world where you will find all the layers laid out that way. Often layers are duplicated or missing; occasionally they come in the wrong order (old layers on top of young layers). For example, they cite the Grand Canyon as an excellent example of the time scale, because it has Pre-Cambrian rocks on the bottom and Permian rocks on top, but there are some layers (as much as 20 million years worth) missing from the middle, with no evidence to explain where they went. Why are the youngest rocks from the Permian period? What happened to the quarter of a billion years worth of rocks that supposedly should have been laid down on top of the Permian? As for those older rocks on top of younger ones, if they cannot be ignored it is explained that some mighty geologic force flipped them over. If that is so, where is the gravel or breccia that is normally produced when two huge rocks scrape against one another? And wouldn't allowing the moving of those rocks by a titanic force be an admission that the theory of catastrophism might be valid after all? It's easier to believe that younger rocks are always laid down on top of older ones, and that our dating method is mixed up.
The Pitfalls of Radioactive Dating
Is there any accurate way to measure the age of rocks and fossils? How about the ones using radioactives, like carbon-14 or potassium-argon? They are scientifically accurate, aren't they?
It looked that way when W. F. Libby first introduced this technique to the world in 1949. Since then, however, so many problems have come up that even Dr. Libby stopped believing in it as a reliable "clock." The theory behind it is as follows: every living thing has in it a tiny amount of carbon-14, a radioactive isotope that differs from regular carbon (carbon-12) in that it has eight neutrons per atom, rather than six. When the organism dies, it stops taking in carbon-14, and the carbon-14 starts to decay into nonradioactive nitrogen-14. The rate of decay is slow but measurable, a time span we call a "half-life" lasting 5,730 years. This means that 5,730 years after death, half the carbon-14 will be left; after 11,460 years (two half-lives) one fourth of it will be left, and after 50,000 years the amount of carbon-14 remaining will be too small to measure.
All this would be a fine and dandy way of dating fossils that are less than 50,000 years old if we could assume that there has always been the same amount of carbon-14 in the environment as there is now. Unfortunately, there have been enough faulty readings on objects to cast serious doubt on that assumption, especially if we know the actual age from another source. Dr. Robert F. Whitelaw, Professor of Nuclear and Mechanical Engineering at the Virginia Polytechnic Institute, reported in 1970 that of the 15,000 samples of once-living matter that had been tested between 1950 and 1970, all but three of them were datable. This included stuff that was supposedly too old to date. For example, most of the Earth's coal is believed to have formed during the Carboniferous Period (300 million years ago), but one coal sample yielded an age of only 4,250 years, while another was even younger--1,680 years old; radioactive carbon has even been found in diamonds. Ridiculously old ages have been produced as well; the mummified bodies of some seals known to have been dead for thirty years old tested out as being 3,000 years dead, and a living(!) mollusk was dated 3,000 years old.(8)
After carbon-14, the most popular way to date fossils is the potassium-argon method, which measures the decay of potassium-40 into argon, a process with a half-life of just over 1 billion years. Similar faulty dates have come up using this method. For example, the Journal of Geophysical Research reported that some lava rocks from Hualalai, Hawaii, are known to have been formed by volcanic eruptions in 1800 and 1801, yet they show ages ranging from 160 million to 3 billion years old.(9) When Louis Leakey applied potassium-argon dating to his most famous discovery, Zinjanthropus, he got a date of 1,750,000 years, but a few years later some other bones from the same site got a carbon-14 test that yielded an age of only 10,100 years.(10) These are not isolated reports:
"Rock samples from 12 volcanoes in Russia and 10 samples from other places around the world, all known to be of recent age (formed within the last 200 years), when dated by the uranium-thorium-lead method gave ages varying from millions to billions of years!"(11)
Dr. L. Hallonquist, a Canadian chemist, collected such reports from Russia, Germany, France, Norway, Holland, the United States, and other countries. He came to this conclusion:
"The startling fact now coming to light, namely that the daughter isotopes or elements on which the dates are calculated, instead of being accumulated in the rocks over long periods of time during the decay of the parent radioactive material, entered the rocks at the time of their formation from the liquid magma, is indeed devastating to the whole system of radiometric rock dating. The new findings strike at the very heart of radiometric systems of rock dating and make them worthless. In fact, if taken to their logical conclusion, these new results indicate a relatively young age, of at the most a few thousand years, for all rocks, instead of the extreme billions of years previously postulated."(12)
Dr. Melvin Cook, a Nobel Prize winner and Professor of Metallurgy at the University of Utah, points out that carbon-14 is produced when cosmic rays and solar radiation strike the Earth's atmosphere. Previously I pointed out that our main barrier to space radiation, the magnetic field, is decreasing. Well, according to Dr. Cook, if that is the case, then in the past less carbon-14 would have been formed, meaning that objects tested will show artificially old dates because they had less carbon-14 in them to start with. He goes on to suggest that we reduce the apparent age of any tested sample by 20% for 1,000 years, 30% for 4,000 years, and anything that is more than 12,500 years old will show up as infinitely ancient.
Because of these problems, since the 1970s some archaeologists have experimented with an alternate method: tree-ring dating. Most of us know that a typical tree lays down a new layer of growth every year, which shows up as rings in the trunk and branches. In places where carbon-14 dates have proved unreliable, like Stonehenge and various Indian pueblos in the southwestern U.S., they have done carbon-14 tests on locally found wood of a known age (figured out by counting the rings) to get new dates they are more willing to accept. So far the results have been favorable, but we must remember that tree rings can be unreliable, too. Rings are produced by drastic changes in weather, so in a year with several very heavy rains, separated by a long dry spell, trees can produce two rings. If they grow on a slope, rapid water runoff can produce even three rings, and one side of the tree will have more rings than the other. Finally, the oldest living trees, the redwoods and bristlecone pines of California, are between 4,000 and 6,000 years old, so tree-ring dating cannot be used on an object much older than the beginning of human history, a time frame much smaller than that claimed by radioactive dating. This means that tree-ring dating can only be considered a general guide.
Back to the Beginning
Now that I have shown that we can't trust the dates put on rocks and fossils, let us check out the fossils themselves, starting with the ones in the "oldest" rocks. According to evolutionists, the vast majority of the Earth's past (87%) is labeled as the Pre-Cambrian Era. On the time chart you will notice that I put some question marks in the space marking major life forms for the Pre-Cambrian Era. This is due to a lack of index fossils; very few fossils have come to us from what they call Pre-Cambrian rocks; just some algae, bacteria, and a few worms and jellyfish. In the Cambrian period which follows, we can find fossils representing every major group of invertebrates except the insects, so the scientists expected to find the creatures they evolved from in Pre-Cambrian rocks. But instead the first pages of the geologic book are virtually blank; no evidence of how a protozoan turned into a worm, or where sponges, shells and lobsters came from. This is just what we would expect if the Pre-Cambrian rocks are those which were laid down during or before the six days of creation.
Then we cross the imaginary line between Pre-Cambrian and Cambrian rocks, and bammo! We find invertebrates crawling or swimming all over the place, in all different sizes and shapes. And these were not simple creatures; one of the most common, the trilobite, had the most complex eyes ever found. For lack of evidence the evolutionists have to draw family trees of invertebrates with dotted lines and question marks between every phylum to show how they think they are related to one another. Usually they explain this by saying that the Pre-Cambrian creatures were soft-bodied, and unlikely to leave fossils until they evolved shells and exoskeletons. That is a cop-out; remember that we have some Pre-Cambrian jellyfish, and what creature could have a softer body than that?
In the next geologic period, the Ordovician, the first vertebrate fossils, the fishes, are found. This means that either the Cambrian or the Ordovician rocks should contain specimens of the invertebrate which evolved into the first fish. Again the evidence is nowhere. No scientists--not one!--can tell you what phylum vertebrates evolved from. Not even the most determined atheistic evolutionist can point to a worm, starfish, snail or crustacean, and say, "This is the evolutionary link between vertebrates and invertebrates." They have to accept on faith that the ancestor of vertebrates was a small marine animal, perhaps something resembling a flatworm. Surely over a period which supposedly spanned more than a hundred million years, the fossil for the transitional life form between vertebrates and invertebrates would have been buried somewhere. The fact that we have not found one after nearly two centuries of searching should cast doubt on the whole evolutionary story of where we came from, and that alone suggests that we have made a mistake somewhere. We could just stop with that, and go to another subject. However, I have a feeling that an evolutionist reading this is not yet convinced of the need to change accepted ideas, so let us consider more evidence.
The Fish That Walked
According to the evolutionary story the first plants and animals (insects and scorpions) to live on land appeared during the Silurian period. The next period, the Devonian, is supposedly when the first land vertebrates, the amphibians, arrived on the scene. Where did the amphibians come from? Well, a type of fish called the lobe-fin evolved that could breathe air and had fins strong enough to drag itself across mud. But why would a fish evolve landgoing features? Presumably to escape ponds that were drying up or were poisoned by rotting plants. After a few million years of doing this, along came the first salamander, which still laid fishlike eggs in the water, but whose fins were no longer fins but feet.
Again, all would be fine and dandy if we could find some transitional life forms to illustrate the story, but the record is blank. Fish are fish, frogs and salamanders are frogs and salamanders, but we have never found a creature that is in-between. In no museum will you find a fossil of a fish with toes where its fins should be. And the differences between fish and amphibians are quite drastic ones: lungs vs. gills, legs firmly attached to a backbone instead of weak fins which cannot hold up the fish's body out of water. All we have to show the transition are some pictures drawn by imaginative artists.
The most famous of the lobe-fins is a queer-looking fish called a coelacanth (pronounced "see-la-canth"). This fish has never been found in rocks dated less than 70 million years old, so for decades scientists thought they died out with the dinosaurs. Imagine their surprise when some African fishermen caught a live one in 1938! A few more have been captured since then, and in 1987 divers took movie cameras into the waters between Africa and Madagascar to film coelacanths in their natural habitat. And that's not all; a second species of coelacanth was discovered in the waters around the Indonesian island of Sulawesi in 1998. Interestingly enough, the modern coelacanth shows no signs of evolving into a land animal; on the contrary, it spends most of its time 300-700 feet underwater, and only gets caught when it strays into a fishing net on its occasional surface visits.
Evolution teaches that when a superior life form develops, the one it is replacing becomes extinct. Sometimes, however, the older creature lives on without any physical changes for millions of years. Scientists call such creatures "living fossils," as if to say, "Here is something that should have died out millions of years ago, but it is still alive today. Isn't that amazing?" Examples of living fossils include the coelacanth, turtles, opossums, and sharks, all supposedly unchanged after an amazing amount of time.
While we are on the subject of transitions and "living fossils," let us consider the case of a really unusual animal--the duckbilled platypus. For those of you who aren't familiar with this oddball from Australia, the platypus seems to be put together with spare parts from mammals, birds and reptiles. It is warm-blooded, has hair and a beaverlike tail, and feeds its young with milk, all features that we associate with mammals. However, it also has a broad duck bill, webbed feet, and lays eggs (features we expect from birds); finally there are reptile-like shoulder bones, and reptile-like poisonous claws on its legs. Biologists have never been able to completely figure out this creature; it has the characteristics of too many different animals to have evolved from any one of them; nor can they say it is evolving into something else, since all of its parts are fully functional and it does just fine in the streams where it lives. In fact, when the first platypus specimen was sent to London, the British scientists thought it was some kind of joke, and tried to remove the bill to find out how it had been attached to the pelt in the first place. Might I venture to say that the platypus is evidence that God has a sense of humor, and that it also takes a sense of humor for Him to create and deal with characters like us?
The Terrible Lizards
Anyway, back to the geologic chart. After the Devonian came the Carboniferous period, when most of the world's coal is believed to have formed. This is considered the age when amphibians were dominant, but the amphibians had one liability that kept them from ruling the land completely: they have to lay their eggs in water. This was solved when one amphibian produced a hard-shelled egg that could be laid on land without drying out, and thus the first reptile came into existence. Again we see major changes in physiology--this time in eggs--and no transitional fossils have been found to show how the shelled egg developed. The oldest land eggs ever found come from Permian rocks, and are virtually identical to those laid by today's alligators and lizards.
The next chapter in the evolutionist's book tells us that the shelled egg was such a big success that during the next four geologic periods (Permian, Triassic, Jurassic and Cretaceous) reptiles evolved and diversified to fill every available ecological niche. Some grew hair and turned into the first mammals; some went back to the water and became sea monsters like the icthyosaurus and plesiosaurus; other grew wings and became pterodactyls. And some simply got bigger and bigger, becoming those creatures whose name means "terrible lizards"--the dinosaurs.
One of the things you will read about in just about every science book is that the dinosaurs died out between 60 and 70 million years ago, and no one knows why they became extinct. All sorts of ideas have been suggested for over a century. First they looked for a natural cause:
1. A general change in climate made the earth too cold, and/or killed off the food supply.
2. Dinosaurs were careless about where they left their eggs, and the early mammals ate them.
3. The glands which made them giants also made them sick.
When none of these theories convinced everybody, they started looking for a cause in outer space. Some suggested that a nearby star (less than 50 light-years away) went nova, and it spewed out enough nuclear radiation to kill everything too big to take cover. Others have suggested that a comet or asteroid collided with the earth, and the fallout from that blast caused a "nuclear winter" that wiped out most of the earth's life. This theory is currently the most popular, and recently one scientist pointed to the remnant of an ancient crater in Mexico's Yucatan peninsula, and declared that this is where the "dinosaur killer" impacted. Another has proposed that there is a planet or small star somewhere in deep space, and about once every 25 million years it comes into the inner solar system, dragging with it a stream of comets and meteors to bombard the Earth with (Velikovsky would be proud!). The inventor of this theory went so far as to give his imaginary killer planet a name--Nemesis.
But can we be sure the dinosaurs died out millions of years before the first men appeared? Cartoonists and movie makers never get tired of ideas about what it would be like if dinosaurs and people were around at the same time. A few years ago a fantasy book called Dinotopia showed vivid pictures of a lost continent where dinosaurs and people lived and worked together; it sold so well that Dinotopia's author produced other books, calendars, a TV mini-series, etc. And the 1993 movie Jurassic Park suggests that some day scientists will use fossil DNA to create dinosaurs with an attitude; Jurassic Park and its sequels were among the most popular movies ever made. In Job 40 and 41 God describes the two greatest animals He created, Behemoth and Leviathan; both of them resemble dinosaurs more than any animals alive today. There are also the dragon myths: so many ancient cultures have stories about dragons and sea serpents (Europe and China, to name just two), that one has to wonder if they saw a dragon-like creature; a dinosaur fits the bill very well.
Perhaps we have all this because there once was a time when dinosaurs and people interacted. The Paluxy River Beds, near Glen Rose, TX, is a rock formation that testifies to this. Dr. Clifford Burdick, an Arizona geologist, reported finding dinosaur and human footprints in the same rock! The human footprints are very large (up to fifteen inches long), but creationists have no trouble with that because Genesis 6:4 tells us that there were giants among our pre-flood ancestors. The problem is their location--how could a rock containing two sets of tracks take 60 million years to harden? An attempt was made to date the formation, using a strip of coal made from a tree branch that fell across the tracks; a carbon-14 test reported it was only 12,000 years old. That by itself should warn us that something is wrong with our accepted theories.
Some scientists have declared the human footprints to be a hoax, but if anything, the three-toed dinosaur tracks look more like fakes. Others (Stephen Jay Gould, for instance) have suggested that the human tracks really come from some kind of dinosaur we haven't found the rest of yet. I'm not holding my breath; all the dinosaur tracks I am familiar with are either bird-like if the dinosaur walked on two legs, or round and elephant-like if they walked on all fours.
Why are so many scientists shouting, "Say it isn't so!" about the Paluxy River tracks? To prove they are genuine would overturn one of evolution's most basic assumptions, and a lot of paleontologists would have to give up their jobs and become truck drivers instead!
Finally there is a very remote possibility that some of these monsters are still alive today. In Africa are some rock paintings of a snake-necked creature that resembles a brontosaurus more than a giraffe, which are not more than a thousand years old. As recently as the 1980s there were reported brontosaurus sightings in the swamps of the Congo; the natives called it mokele-mbembe, meaning "rainbow-shaped neck." And a lot of the so-called "sea-serpents" fit the description of a plesiosaurus. In 1977 some Japanese fishermen got the shock of their lives when a badly decayed, long-necked carcass drifted into their nets off the coast of New Zealand; it looked more like a plesiosaurus than anything else. You probably have also heard about the Loch Ness monster, a plesiosaurus-like creature that lives in a lake in Scotland but has never been clearly seen. Scientists have been trying to catch or take pictures of the Loch Ness monster for decades, but with a price of over £750,000 on its head, can anyone blame the beastie if it prefers to stay hidden?
A Feathered Flying Machine
Of course, if a live dinosaur ever turns up somewhere, it will be called a living fossil, just like the coelacanth. Personally, I am glad they don't live in my neighborhood; they would make life a lot more complicated! ("Yes, boss, I know I'm late for work. Did you hear the news? There's a tyrannosaurus taking a nap on I-4 and it's got traffic backed up all the way to Sanford!")
In the 1970s it was suggested that the dinosaurs didn't really become extinct; some of the smaller ones evolved wings and feathers and are still with us today, as birds. Now paleontologists are hard at work to prove that this happened, by looking for a link between dinosaurs and birds; they see a small meat-eater like deionychus or velociraptor as the most likely candidate. So next time a duck flies overhead, I guess it's politically correct to say, "Duck! A dinosaur!"
Yeah, right. So now we are supposed to believe that a multi-ton, thick-skinned lizard is the ancestor of nature's most perfect flying machine. The bird is wonderfully designed for flight, with many features that don't appear in your typical reptile, like a four-chambered heart and hollow bones. It makes about as much sense as mounting a pair of surfboards on the sides of a van and expecting it to fly like a DC-3. Finally, nobody is trying to explain why the ancestor of the birds must be a dinosaur with a lizard-like (saurischian) pelvis, rather than one of the many "bird-hipped" (ornithschian) species. If the evolutionary story is true, then we ought to tell the folks at the Smithsonian to remodel the National Air & Space Museum, because the Wright Brothers' airplane will have to take second place to the first airborne dinosaur!
As in the previous sections, we have here a situation where we are expected to accept on faith that one life form made a series of critical changes to become something different, because we don't have the fossil evidence to prove it. The feather is quite a complicated structure, with all kinds of hooks and barbs to keep itself rigid and lightweight at the same time. Supposedly it evolved from the simple flat scales of reptiles, but where's the transitional fossil?
I can now hear the evolutionist saying, "Aha, but we do have the transitional fossil; we have archaeopteryx!" The fossil we have of archaeopteryx shows a number of primitive features, including reptile-like teeth, claws on its wings, and a small breastbone (which means it was a poor flyer). Yet it also has fully developed feathers, and could fly, so even evolutionists concede it was a fully developed bird. As for the "primitive" features, I'll say just a few words about them.
1. The teeth aren't really that remarkable. True, there are no toothed birds today, but every other class of vertebrates comes in toothed and toothless forms. We have fish with teeth and fish with no teeth; reptiles with teeth and reptiles with no teeth (turtles); mammals with teeth and mammals without teeth (anteaters); people with teeth and people without teeth! Why couldn't God have created toothy birds at first, to fly with the toothless ones that are still with us today?
2. The claws on the wings aren't unique either. There are three species of birds today which possess claws: the hoatzin of South America, and the touraco and ostrich of Africa. None of them are good flyers (the ostrich doesn't fly at all); if they were extinct, and one of them was found as a fossil, the paleontologists might think this was a primitive "halfway bird."
3. The archaeopteryx fossil was dated to the Jurassic period, about 150 million years ago. Recently another fossil bird was found in a rock dated to be 75 million years older, and it looks even less like a reptile than archaeopteryx does. Since offspring cannot be the fathers of their parents, this means that archaeopteryx is not the missing link; now the paleontologists have to go look for another one. Meanwhile they have to use their imagination to fill the blanks (some textbooks sport a picture of a lizard with feathers called "pro-avis," and suggest that the ancestor of birds looked like this).
In 1999, the National Geographic Society announced the discovery of "feathered dinosaurs" in northeast China's Liaoning province. One fossil caused such a sensation that they dubbed it archaeoraptor ("ancient bird of prey") and rushed to publish an article about it, entitled "Feathers for T. rex? New birdlike fossils are missing links in dinosaur evolution." The article, which appeared in November 1999, was richly illustrated with speculations on what these feathered dinosaurs looked like, even suggesting that a baby tyrannosaurus had a coat of down like a duckling, only to shed it when it got big. Then the fossil went on public display in Washington D.C., while news reports, Internet sites and TV specials announced the find worldwide.
A few scientists challenged such claims immediately. Larry D. Martin, a paleontologist from the University of Kansas, argued that nobody could prove that the feather-like impressions in the rock surrounding the bones were really feathers, while Storrs L. Olson, the curator of birds at the Smithsonian, accused National Geographic of committing sensationalist tabloid journalism. This prompted one of Archaeoraptor's supporters, Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology (in Beijing, China), to go to Liaoning and check out the rock slab where it had been discovered. What he found was embarrassing; the Chinese farmer who lived on the property had dug up several pieces of fossils, and joined a bird's body with a dinosaur's tail to produce a specimen that was complete enough to be worth something. In other words, archaeoraptor was a hoax, much like one we'll look at in the next chapter--Piltdown Man.
This is as good a place as any to point out that there are many characteristics in animals that are so complicated, they would be useless if they appeared in a less than fully developed form. The wings of the bird and the pterodactyl, for instance. A good change in an organism's makeup is supposed to improve its chances for survival, but if some lizard was born with half-developed wings, what would it do with them? It could not fly with them, and they will probably keep it from running very fast. How will it catch its food or run away from its enemies? If it tried to fly with them--splat!--no more lizard. A creature with half-developed wings is worse off than one with no wings at all.
Likewise, how could the bombardier beetle's unique cannon evolve, if it would cook the beetle that tried to blast a predator before it was fully developed? How could any form of symbiosis (beneficial interaction between two life forms) develop? Flowers and bees cannot survive without each other, so which came first?(13) How could cleaner fishes like the wrasse survive if they tried to clean the mouth of a big fish that had not yet developed the instinct to let them work without eating them? What good would our eyes be if the cornea and lens evolved before the retina did? I could go on and on listing characteristics that show the work of intelligent design, rather than the chance acquisition of one characteristic at a time. I am reminded of what the naturalist William Paley (1743-1805) said about such ideas: "If the human eye came by chance, then so could the telescope!"
This is the End of Chapter 4.
FOOTNOTES
1. Velikovsky, Earth In Upheaval, Garden City, NY: Doubleday & Co., 1955, pg. 202.
2. Coffin, Harold G., Creation--Accident or Design?, Washington, D.C., Review & Herald Publishing Association, 1969, pgs. 73-74.
3. Ladd, Harry S., "Ecology, Paleontology and Stratigraphy," Science, Vol. 129, January 9, 1959, pg. 72.
4. Stokstad, Erik, "Tyrannosaurus rex Soft Tissue Raises Tantalizing Prospects," Science, Vol. 307, March 25, 2005, pg. 1852. For pictures, check out "Scientists recover T. rex soft tissue" at MSNBC.com.
5. Noorbergen, Rene, Secrets of the Lost Races, New York, The Bobbs-Merrill Company Inc., 1977, pg. 16.
6. Coffin, pg. 76.
7. Plug, plug.
8. "Time, Life and History in the Light of 15,000 Radio Carbon Dates," The Creation Research Society Quarterly, June 1970, pgs. 56-59.
9. Journal of Geophysical Research, Vol. 73/14, July 15, 1968.
10. L. Hallonquist, Radio-Active Dating, pg. 2; and Science Journal, November, 1968.
11. Gish, Duane T., "Dating of the Moon Rocks," Creation Science Report, Vol. 1, No. 2, March/April 1972.
12. L. Hallonquist, The Age of the Earth, pgs. 4 and 5.
13. My favorite example of symbiosis is similar to the flower and the bee; the relationship between the calimyrna fig and the fig wasp. There are many steps involved in that relationship, and if any of them didn't work out, both the fig and the fig wasp would have become extinct by now. For a start, the fig has the most unusual structure of any fruit I have ever seen; the flowers are on the inside of the fruit, instead of the outside. And unlike most plants, figs come in sexes, with male and female flowers on different plants, so if it wasn't for the fig wasp, which is tiny enough to get inside the fig, pollination of those flowers would be impossible. For those who are unfamiliar with the relationship, check out the Calimyrna Figs in California page to read the whole story, and the next time you eat a fig, remember that it's the life work of an insect the size of a gnat. I dare anyone to show me how all that could happen without intelligent design!
The Genesis Chronicles: A Proposed History Of The Morning Of The World
Chapter 4: EVOLUTION AND THE FOSSIL RECORD
This chapter covers the following topics:
What We Should Find
How Are Fossils Made?
The Geologic Table
The Pitfalls of Radioactive Dating
Back to the Beginning
The Fish That Walked
The Terrible Lizards
A Feathered Flying Machine
Go to Page Navigator
What We Should Find
Now we have reached the area where evolution feels strongest--the fossil record. Fossils are the scientist's books on the earth's past; if there is proof that evolution happened, this is where it will be found. If the earth is really billions of years old, and every life form of today has evolved from something else, then we should find countless examples of fossils representing plants and animals that are not quite one thing, not quite another. The impression that this is true is so strong that when confronted with the idea that evolution might not be true, the ordinary person is likely to ask, "Then where did all those fossils come from?" Some Christians inclined to believe in creation even wonder if dinosaurs really existed; they think the fossil record is a complete but bogus testimony, some kind of satanic plot.
But is the fossil record really complete? When Darwin wrote The Origin of Species paleontology was a new science, only a few decades old, so we had studied only a few fossils to that point. Darwin did not have a single fossil to prove his theory--he admitted he did not have any--but he was optimistic that eventually they would turn up. It has been nearly a century and a half since then, and in our museums we have fossils representing over a quarter of a million extinct species. If evolution is correct, than the laws of probability tell us that many of those fossils will represent transitional life forms, creatures in the process of evolving from one species to another. It should be possible to go to a great natural history museum like those in Chicago, New York or Washington, D.C., and see transitional fossils all over the place. On the other hand, if our view of creation is accurate, then you will find in the fossil record evidence of life forms coming into existence fully developed, without ages of development preceding each one. According to creationism, we will find fossils from previous ages, but trees will always be trees, insects will always be insects, fish will always be fish, lizards will always be lizards, monkeys will always be monkeys, and people will always be people.
How Are Fossils Made?
To begin with, we must look at the way in which fossils are made. Typically, an animal or plant dies and is quickly buried before scavengers and decay can get to it. Then pressure turns the surrounding sand or soil into rock. After that water seeps in, and bit by bit, it dissolves part of the organism. Every time it does so it replaces the molecules it removes with molecules from the surrounding rock. At last none of the original organism is left. There is a copy of it made out of stone instead.
We call this process petrification, and it can happen in just a few years under the right circumstances. When on speaking tours, Dr. Ken Ham likes to show a picture of a floppy beach hat somebody left in an Australian mine in the 1930s, to be found 50 years later; it was a soft hat originally, but it's a hard hat now! For uniformitarianism, and thus evolution, to be valid, there must be places around today where fossils are being formed regularly, by natural processes which geologists can identify. Can anybody name such a place? I have never heard of one, despite two centuries of digging and searching in the rock beneath our feet.
Let us consider, for example, the requirement that the organism has to be immediately buried. Suppose one day you brought home a cow, put it in the backyard and shot it (Don't do this in the driveway or the neighbors will complain!). Then over the next eleven weeks you went out from time to time, studied the carcass and took notes. How long do you think it would take to become a fossil? It probably won't become a fossil at all. On the Great Plains in the late nineteenth century there was death on a massive scale, when hunters shot buffalo by the millions, but because the conditions for fossil formation were not there, nobody has found one fossil buffalo dating back to the days when the prairie was the white man's "happy hunting grounds."
Now let's consider the origin of the most common vertebrate fossils, those of fish. Immanuel Velikovsky had this to say about the subject:
"When a fish dies its body floats on the surface or sinks to the bottom and is devoured rather quickly, actually in a matter of hours, by other fish. However, the fossil fish found in sedimentary rock is very often preserved with all of its bones intact. Entire shoals of fish over large areas, numbering billions of specimens, are found in a state of agony, but with no mark of a scavenger's attack.
"The explanation of the origin of fossils by uniformity and evolution contradicts the fundamental principle of these theories: Nothing took place in the past that does not take place in the present. Today no fossils are formed."(1) [Italics are mine, C.K.]
Geologist Harold G. Coffin, of the Geoscience Research Institute in Berrien Springs, MI, wrote about an experiment in the formation of fish fossils conducted by two scientists named Zangerl and Richardson. Here are the results:
"In attempting to evaluate the rate of fossilization in the Pennsylvania black shales of Indiana, they placed dead fish in the protecting wire cages and dropped them into the black muds at the bottom of several Louisiana lagoons or bayous. These black muds are thought to resemble the sediments from which the dark shales were derived. To the great surprise of the investigators, fish weighing from one-half to three-fourths of a pound were found to have all the soft parts reduced and all the bones completely disarticulated in six and one-half days! Decomposition to the state of total disarticulation apparently occurs at great speed, perhaps in less time than indicated above, since none were checked before six and one-half days. Delicate fossil fish showing every minute ray and bone in position are common and must represent a burial by oxygen- and bacteria-excluding sediments within hours of death if this experiment is a valid indication."(2)
That ought to show us that you can't get fish fossils by dumping cyanide into an aquarium! The process which fossilizes fish is very uncommon, if it is taking place anywhere today, but fish fossils are not rare. It is estimated that eight hundred billion fish fossils are contained in the Karoo rock formation of South Africa. Geologist Hugh Miller tells us that the fish-containing Devonian rocks of England are full of fish that died violently, in an area that covers more than ten thousand square miles. Closer to home, Harry S. Ladd of the US Geological Survey says that "more than a billion fish, averaging six to eight inches in length, died on four square miles of bay bottom."(3) And rocks containing sea fossils (fossils of fish and shells) are found over more than 75% of the earth, even on the slopes of Mt. Everest. Catastrophists have long known that only a worldwide disaster involving water, namely Noah's Flood, could have produced death on such a large scale.
Even more amazing is the recent announcement of the discovery of a tyrannosaurus rex skeleton whose bones contained soft tissue. In a broken thighbone, between the expected hard minerals, they found "blood vessels--still flexible and elastic after 68 million years--and apparently intact cells."(4) It is nearly impossible to preserve soft tissues for a few thousand years (usually subzero temperatures and an extremely low humidity are required), so as we go to the press, evolutionists are rushing to explain how soft tissues can last for 68 million years.
Another place where faulty reasoning is used to explain fossil formation is in the world's vast coal deposits. Since coal is by nature a "fossil fuel," we have discovered many fascinating plants and animals in coal mines, including a number of dinosaurs. Rene Noorbergen reports that in the Geisental lignite deposits of Germany, leaves have been so well preserved that they still are green with chlorophyll; there are also beautifully colored tropical beetles with the soft parts of their body, including the contents of their intestines, preserved intact. Under normal conditions such materials decay or lose their color within a few hours of death, meaning that their burial in an anaerobic medium had to be done right away.(5)
Dr. Coffin points out some interesting facts about how coal is made:
"The thickness of peat needed to produce one foot of coal depends on a number of factors, such as the type of peat, the amount of water in the vegetable matter, and the type of coal. The scientific literature on coal gives figures ranging from a few feet to as many as twenty. Let us assume that ten feet would be near the average figure. On this basis, a coal seam thirty feet thick would require the compression of 300 feet of peat. A 400-foot seam of coal would be the result of a fantastic 4,000 feet of peat.
"There are few peat bogs, marshes, or swamps anywhere in the world today that reach 100 feet. Most of them are less than 50 feet. A much more reasonable alternative theory is that the vegetable matter has been concentrated and collected into an area by some force, undoubtedly water. . . .
"The concept of a global deluge that eroded out the forests and plant cover of the pre-Flood world, collected it in great mats of drifting debris, and eventually dropped it on the emerging land or on the sea bottom is the most reasonable answer to this problem of the great extent and uniform thickness of coal beds."(6)
Another problem overlooked is that often whole fossilized trees are found in coal, stretching through several layers of it. Since uniformitarianism tells us that no more than a few inches of peat are produced per year, by such reasoning some of these trees would have to stand for thousands of years before they were completely buried. Look around you; do you see any dead trees that have been standing for more than a few years? I know in my neighborhood that woodpeckers, termites and carpenter ants will bring down a dead tree in only a year or two, so how could so many trees have lasted long enough to be buried? Again we have a situation in the rocks that only makes sense if a sudden catastrophe involving rapid burial is the cause. Some of those trees are buried upside down; they certainly didn't grow that way!
The Geologic Table
As I pointed out in Chapter 1, the geologic scale of the earth's history found in most science books was drawn up by Charles Lyell before the theory of evolution was developed. A few changes have been made since then (as recently as the 1940s they thought that the world could not be more than two billion years old) but essentially geologists and paleontologists are using the same chart today. It generally looks like this:
The Geologic Table Era Period Major Life Forms How Long Ago (millions of years)
CENOZOIC Quaternary The weirdest creature of all 1 to now
Tertiary The age of mammals 63 to 1
MESOZOIC Cretaceous T. Rex & the flowers 135 to 63
Jurassic Birdy & Bronty 180 to 135
Triassic Tiny mammals & dinosaurs 225 to 180
PALEOZOIC Permian Weird reptiles 280 to 225
Carboniferous The creation of coal 345 to 280
Devonian Fish & forest 405 to 345
Silurian Life's a beach 425 to 405
Ordovician Go fishin' 500 to 425
Cambrian Hard bodies 600 to 500
PRE-CAMBRIAN ??? Before 600
Note: The Cenozoic Era is often divided into seven shorter periods called epochs, rather than just two periods. From oldest to youngest, the names of those epochs are Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene (Recent).
Now when they classify new fossils, scientists immediately go to this chart to find out what time frame to place them in. How do they do that? Do they use a sophisticated technique like radiocarbon dating? No, more often they look for an "index fossil" in the same rock. They have long believed that rocks found in two different places which contain the same fossils must be the same age. Because of this, a rock containing a trilobite or brachiopod is expected to come from the Cambrian period, and rocks with dinosaur bones in them are automatically dated to the Mesozoic era. This has led to some circular reasoning, meaning that we can trust none of the dates assigned to rocks. For example:
You: "How old is this fish fossil?"
Paleontologist: "40 million years old."
You: "How do you know that?"
Paleontologist: "Because it is in a rock that is 40 million years old."
Then you go to a geologist with the fossil and ask: "How old is this rock?"
Geologist: "40 million years old."
You: "Did you use potassium-Argon dating to find that out?"
Geologist: "No."
You: "Then how do you know it is 40 million years old?"
Geologist: "Because it has a 40-million-year-old fossil in it."
This means that the whole geologic table is based not so much on careful research as on it is on shaky assumptions that could collapse when exposed to enough evidence favoring a young, created Earth. I believe that such evidence does exist, but that most people have not opened their eyes to the truth. Duane Gish wrote a whole book on the subject in 1973 entitled Evolution: The Fossils Say No!, and nowadays you may find a larger, more up-to-date version with the title Evolution: The Challenge of the Fossil Record.(7)
One such problem is that the only place where a complete geologic table like the one shown can be found is in the textbooks. There is no place in the real world where you will find all the layers laid out that way. Often layers are duplicated or missing; occasionally they come in the wrong order (old layers on top of young layers). For example, they cite the Grand Canyon as an excellent example of the time scale, because it has Pre-Cambrian rocks on the bottom and Permian rocks on top, but there are some layers (as much as 20 million years worth) missing from the middle, with no evidence to explain where they went. Why are the youngest rocks from the Permian period? What happened to the quarter of a billion years worth of rocks that supposedly should have been laid down on top of the Permian? As for those older rocks on top of younger ones, if they cannot be ignored it is explained that some mighty geologic force flipped them over. If that is so, where is the gravel or breccia that is normally produced when two huge rocks scrape against one another? And wouldn't allowing the moving of those rocks by a titanic force be an admission that the theory of catastrophism might be valid after all? It's easier to believe that younger rocks are always laid down on top of older ones, and that our dating method is mixed up.
The Pitfalls of Radioactive Dating
Is there any accurate way to measure the age of rocks and fossils? How about the ones using radioactives, like carbon-14 or potassium-argon? They are scientifically accurate, aren't they?
It looked that way when W. F. Libby first introduced this technique to the world in 1949. Since then, however, so many problems have come up that even Dr. Libby stopped believing in it as a reliable "clock." The theory behind it is as follows: every living thing has in it a tiny amount of carbon-14, a radioactive isotope that differs from regular carbon (carbon-12) in that it has eight neutrons per atom, rather than six. When the organism dies, it stops taking in carbon-14, and the carbon-14 starts to decay into nonradioactive nitrogen-14. The rate of decay is slow but measurable, a time span we call a "half-life" lasting 5,730 years. This means that 5,730 years after death, half the carbon-14 will be left; after 11,460 years (two half-lives) one fourth of it will be left, and after 50,000 years the amount of carbon-14 remaining will be too small to measure.
All this would be a fine and dandy way of dating fossils that are less than 50,000 years old if we could assume that there has always been the same amount of carbon-14 in the environment as there is now. Unfortunately, there have been enough faulty readings on objects to cast serious doubt on that assumption, especially if we know the actual age from another source. Dr. Robert F. Whitelaw, Professor of Nuclear and Mechanical Engineering at the Virginia Polytechnic Institute, reported in 1970 that of the 15,000 samples of once-living matter that had been tested between 1950 and 1970, all but three of them were datable. This included stuff that was supposedly too old to date. For example, most of the Earth's coal is believed to have formed during the Carboniferous Period (300 million years ago), but one coal sample yielded an age of only 4,250 years, while another was even younger--1,680 years old; radioactive carbon has even been found in diamonds. Ridiculously old ages have been produced as well; the mummified bodies of some seals known to have been dead for thirty years old tested out as being 3,000 years dead, and a living(!) mollusk was dated 3,000 years old.(8)
After carbon-14, the most popular way to date fossils is the potassium-argon method, which measures the decay of potassium-40 into argon, a process with a half-life of just over 1 billion years. Similar faulty dates have come up using this method. For example, the Journal of Geophysical Research reported that some lava rocks from Hualalai, Hawaii, are known to have been formed by volcanic eruptions in 1800 and 1801, yet they show ages ranging from 160 million to 3 billion years old.(9) When Louis Leakey applied potassium-argon dating to his most famous discovery, Zinjanthropus, he got a date of 1,750,000 years, but a few years later some other bones from the same site got a carbon-14 test that yielded an age of only 10,100 years.(10) These are not isolated reports:
"Rock samples from 12 volcanoes in Russia and 10 samples from other places around the world, all known to be of recent age (formed within the last 200 years), when dated by the uranium-thorium-lead method gave ages varying from millions to billions of years!"(11)
Dr. L. Hallonquist, a Canadian chemist, collected such reports from Russia, Germany, France, Norway, Holland, the United States, and other countries. He came to this conclusion:
"The startling fact now coming to light, namely that the daughter isotopes or elements on which the dates are calculated, instead of being accumulated in the rocks over long periods of time during the decay of the parent radioactive material, entered the rocks at the time of their formation from the liquid magma, is indeed devastating to the whole system of radiometric rock dating. The new findings strike at the very heart of radiometric systems of rock dating and make them worthless. In fact, if taken to their logical conclusion, these new results indicate a relatively young age, of at the most a few thousand years, for all rocks, instead of the extreme billions of years previously postulated."(12)
Dr. Melvin Cook, a Nobel Prize winner and Professor of Metallurgy at the University of Utah, points out that carbon-14 is produced when cosmic rays and solar radiation strike the Earth's atmosphere. Previously I pointed out that our main barrier to space radiation, the magnetic field, is decreasing. Well, according to Dr. Cook, if that is the case, then in the past less carbon-14 would have been formed, meaning that objects tested will show artificially old dates because they had less carbon-14 in them to start with. He goes on to suggest that we reduce the apparent age of any tested sample by 20% for 1,000 years, 30% for 4,000 years, and anything that is more than 12,500 years old will show up as infinitely ancient.
Because of these problems, since the 1970s some archaeologists have experimented with an alternate method: tree-ring dating. Most of us know that a typical tree lays down a new layer of growth every year, which shows up as rings in the trunk and branches. In places where carbon-14 dates have proved unreliable, like Stonehenge and various Indian pueblos in the southwestern U.S., they have done carbon-14 tests on locally found wood of a known age (figured out by counting the rings) to get new dates they are more willing to accept. So far the results have been favorable, but we must remember that tree rings can be unreliable, too. Rings are produced by drastic changes in weather, so in a year with several very heavy rains, separated by a long dry spell, trees can produce two rings. If they grow on a slope, rapid water runoff can produce even three rings, and one side of the tree will have more rings than the other. Finally, the oldest living trees, the redwoods and bristlecone pines of California, are between 4,000 and 6,000 years old, so tree-ring dating cannot be used on an object much older than the beginning of human history, a time frame much smaller than that claimed by radioactive dating. This means that tree-ring dating can only be considered a general guide.
Back to the Beginning
Now that I have shown that we can't trust the dates put on rocks and fossils, let us check out the fossils themselves, starting with the ones in the "oldest" rocks. According to evolutionists, the vast majority of the Earth's past (87%) is labeled as the Pre-Cambrian Era. On the time chart you will notice that I put some question marks in the space marking major life forms for the Pre-Cambrian Era. This is due to a lack of index fossils; very few fossils have come to us from what they call Pre-Cambrian rocks; just some algae, bacteria, and a few worms and jellyfish. In the Cambrian period which follows, we can find fossils representing every major group of invertebrates except the insects, so the scientists expected to find the creatures they evolved from in Pre-Cambrian rocks. But instead the first pages of the geologic book are virtually blank; no evidence of how a protozoan turned into a worm, or where sponges, shells and lobsters came from. This is just what we would expect if the Pre-Cambrian rocks are those which were laid down during or before the six days of creation.
Then we cross the imaginary line between Pre-Cambrian and Cambrian rocks, and bammo! We find invertebrates crawling or swimming all over the place, in all different sizes and shapes. And these were not simple creatures; one of the most common, the trilobite, had the most complex eyes ever found. For lack of evidence the evolutionists have to draw family trees of invertebrates with dotted lines and question marks between every phylum to show how they think they are related to one another. Usually they explain this by saying that the Pre-Cambrian creatures were soft-bodied, and unlikely to leave fossils until they evolved shells and exoskeletons. That is a cop-out; remember that we have some Pre-Cambrian jellyfish, and what creature could have a softer body than that?
In the next geologic period, the Ordovician, the first vertebrate fossils, the fishes, are found. This means that either the Cambrian or the Ordovician rocks should contain specimens of the invertebrate which evolved into the first fish. Again the evidence is nowhere. No scientists--not one!--can tell you what phylum vertebrates evolved from. Not even the most determined atheistic evolutionist can point to a worm, starfish, snail or crustacean, and say, "This is the evolutionary link between vertebrates and invertebrates." They have to accept on faith that the ancestor of vertebrates was a small marine animal, perhaps something resembling a flatworm. Surely over a period which supposedly spanned more than a hundred million years, the fossil for the transitional life form between vertebrates and invertebrates would have been buried somewhere. The fact that we have not found one after nearly two centuries of searching should cast doubt on the whole evolutionary story of where we came from, and that alone suggests that we have made a mistake somewhere. We could just stop with that, and go to another subject. However, I have a feeling that an evolutionist reading this is not yet convinced of the need to change accepted ideas, so let us consider more evidence.
The Fish That Walked
According to the evolutionary story the first plants and animals (insects and scorpions) to live on land appeared during the Silurian period. The next period, the Devonian, is supposedly when the first land vertebrates, the amphibians, arrived on the scene. Where did the amphibians come from? Well, a type of fish called the lobe-fin evolved that could breathe air and had fins strong enough to drag itself across mud. But why would a fish evolve landgoing features? Presumably to escape ponds that were drying up or were poisoned by rotting plants. After a few million years of doing this, along came the first salamander, which still laid fishlike eggs in the water, but whose fins were no longer fins but feet.
Again, all would be fine and dandy if we could find some transitional life forms to illustrate the story, but the record is blank. Fish are fish, frogs and salamanders are frogs and salamanders, but we have never found a creature that is in-between. In no museum will you find a fossil of a fish with toes where its fins should be. And the differences between fish and amphibians are quite drastic ones: lungs vs. gills, legs firmly attached to a backbone instead of weak fins which cannot hold up the fish's body out of water. All we have to show the transition are some pictures drawn by imaginative artists.
The most famous of the lobe-fins is a queer-looking fish called a coelacanth (pronounced "see-la-canth"). This fish has never been found in rocks dated less than 70 million years old, so for decades scientists thought they died out with the dinosaurs. Imagine their surprise when some African fishermen caught a live one in 1938! A few more have been captured since then, and in 1987 divers took movie cameras into the waters between Africa and Madagascar to film coelacanths in their natural habitat. And that's not all; a second species of coelacanth was discovered in the waters around the Indonesian island of Sulawesi in 1998. Interestingly enough, the modern coelacanth shows no signs of evolving into a land animal; on the contrary, it spends most of its time 300-700 feet underwater, and only gets caught when it strays into a fishing net on its occasional surface visits.
Evolution teaches that when a superior life form develops, the one it is replacing becomes extinct. Sometimes, however, the older creature lives on without any physical changes for millions of years. Scientists call such creatures "living fossils," as if to say, "Here is something that should have died out millions of years ago, but it is still alive today. Isn't that amazing?" Examples of living fossils include the coelacanth, turtles, opossums, and sharks, all supposedly unchanged after an amazing amount of time.
While we are on the subject of transitions and "living fossils," let us consider the case of a really unusual animal--the duckbilled platypus. For those of you who aren't familiar with this oddball from Australia, the platypus seems to be put together with spare parts from mammals, birds and reptiles. It is warm-blooded, has hair and a beaverlike tail, and feeds its young with milk, all features that we associate with mammals. However, it also has a broad duck bill, webbed feet, and lays eggs (features we expect from birds); finally there are reptile-like shoulder bones, and reptile-like poisonous claws on its legs. Biologists have never been able to completely figure out this creature; it has the characteristics of too many different animals to have evolved from any one of them; nor can they say it is evolving into something else, since all of its parts are fully functional and it does just fine in the streams where it lives. In fact, when the first platypus specimen was sent to London, the British scientists thought it was some kind of joke, and tried to remove the bill to find out how it had been attached to the pelt in the first place. Might I venture to say that the platypus is evidence that God has a sense of humor, and that it also takes a sense of humor for Him to create and deal with characters like us?
The Terrible Lizards
Anyway, back to the geologic chart. After the Devonian came the Carboniferous period, when most of the world's coal is believed to have formed. This is considered the age when amphibians were dominant, but the amphibians had one liability that kept them from ruling the land completely: they have to lay their eggs in water. This was solved when one amphibian produced a hard-shelled egg that could be laid on land without drying out, and thus the first reptile came into existence. Again we see major changes in physiology--this time in eggs--and no transitional fossils have been found to show how the shelled egg developed. The oldest land eggs ever found come from Permian rocks, and are virtually identical to those laid by today's alligators and lizards.
The next chapter in the evolutionist's book tells us that the shelled egg was such a big success that during the next four geologic periods (Permian, Triassic, Jurassic and Cretaceous) reptiles evolved and diversified to fill every available ecological niche. Some grew hair and turned into the first mammals; some went back to the water and became sea monsters like the icthyosaurus and plesiosaurus; other grew wings and became pterodactyls. And some simply got bigger and bigger, becoming those creatures whose name means "terrible lizards"--the dinosaurs.
One of the things you will read about in just about every science book is that the dinosaurs died out between 60 and 70 million years ago, and no one knows why they became extinct. All sorts of ideas have been suggested for over a century. First they looked for a natural cause:
1. A general change in climate made the earth too cold, and/or killed off the food supply.
2. Dinosaurs were careless about where they left their eggs, and the early mammals ate them.
3. The glands which made them giants also made them sick.
When none of these theories convinced everybody, they started looking for a cause in outer space. Some suggested that a nearby star (less than 50 light-years away) went nova, and it spewed out enough nuclear radiation to kill everything too big to take cover. Others have suggested that a comet or asteroid collided with the earth, and the fallout from that blast caused a "nuclear winter" that wiped out most of the earth's life. This theory is currently the most popular, and recently one scientist pointed to the remnant of an ancient crater in Mexico's Yucatan peninsula, and declared that this is where the "dinosaur killer" impacted. Another has proposed that there is a planet or small star somewhere in deep space, and about once every 25 million years it comes into the inner solar system, dragging with it a stream of comets and meteors to bombard the Earth with (Velikovsky would be proud!). The inventor of this theory went so far as to give his imaginary killer planet a name--Nemesis.
But can we be sure the dinosaurs died out millions of years before the first men appeared? Cartoonists and movie makers never get tired of ideas about what it would be like if dinosaurs and people were around at the same time. A few years ago a fantasy book called Dinotopia showed vivid pictures of a lost continent where dinosaurs and people lived and worked together; it sold so well that Dinotopia's author produced other books, calendars, a TV mini-series, etc. And the 1993 movie Jurassic Park suggests that some day scientists will use fossil DNA to create dinosaurs with an attitude; Jurassic Park and its sequels were among the most popular movies ever made. In Job 40 and 41 God describes the two greatest animals He created, Behemoth and Leviathan; both of them resemble dinosaurs more than any animals alive today. There are also the dragon myths: so many ancient cultures have stories about dragons and sea serpents (Europe and China, to name just two), that one has to wonder if they saw a dragon-like creature; a dinosaur fits the bill very well.
Perhaps we have all this because there once was a time when dinosaurs and people interacted. The Paluxy River Beds, near Glen Rose, TX, is a rock formation that testifies to this. Dr. Clifford Burdick, an Arizona geologist, reported finding dinosaur and human footprints in the same rock! The human footprints are very large (up to fifteen inches long), but creationists have no trouble with that because Genesis 6:4 tells us that there were giants among our pre-flood ancestors. The problem is their location--how could a rock containing two sets of tracks take 60 million years to harden? An attempt was made to date the formation, using a strip of coal made from a tree branch that fell across the tracks; a carbon-14 test reported it was only 12,000 years old. That by itself should warn us that something is wrong with our accepted theories.
Some scientists have declared the human footprints to be a hoax, but if anything, the three-toed dinosaur tracks look more like fakes. Others (Stephen Jay Gould, for instance) have suggested that the human tracks really come from some kind of dinosaur we haven't found the rest of yet. I'm not holding my breath; all the dinosaur tracks I am familiar with are either bird-like if the dinosaur walked on two legs, or round and elephant-like if they walked on all fours.
Why are so many scientists shouting, "Say it isn't so!" about the Paluxy River tracks? To prove they are genuine would overturn one of evolution's most basic assumptions, and a lot of paleontologists would have to give up their jobs and become truck drivers instead!
Finally there is a very remote possibility that some of these monsters are still alive today. In Africa are some rock paintings of a snake-necked creature that resembles a brontosaurus more than a giraffe, which are not more than a thousand years old. As recently as the 1980s there were reported brontosaurus sightings in the swamps of the Congo; the natives called it mokele-mbembe, meaning "rainbow-shaped neck." And a lot of the so-called "sea-serpents" fit the description of a plesiosaurus. In 1977 some Japanese fishermen got the shock of their lives when a badly decayed, long-necked carcass drifted into their nets off the coast of New Zealand; it looked more like a plesiosaurus than anything else. You probably have also heard about the Loch Ness monster, a plesiosaurus-like creature that lives in a lake in Scotland but has never been clearly seen. Scientists have been trying to catch or take pictures of the Loch Ness monster for decades, but with a price of over £750,000 on its head, can anyone blame the beastie if it prefers to stay hidden?
A Feathered Flying Machine
Of course, if a live dinosaur ever turns up somewhere, it will be called a living fossil, just like the coelacanth. Personally, I am glad they don't live in my neighborhood; they would make life a lot more complicated! ("Yes, boss, I know I'm late for work. Did you hear the news? There's a tyrannosaurus taking a nap on I-4 and it's got traffic backed up all the way to Sanford!")
In the 1970s it was suggested that the dinosaurs didn't really become extinct; some of the smaller ones evolved wings and feathers and are still with us today, as birds. Now paleontologists are hard at work to prove that this happened, by looking for a link between dinosaurs and birds; they see a small meat-eater like deionychus or velociraptor as the most likely candidate. So next time a duck flies overhead, I guess it's politically correct to say, "Duck! A dinosaur!"
Yeah, right. So now we are supposed to believe that a multi-ton, thick-skinned lizard is the ancestor of nature's most perfect flying machine. The bird is wonderfully designed for flight, with many features that don't appear in your typical reptile, like a four-chambered heart and hollow bones. It makes about as much sense as mounting a pair of surfboards on the sides of a van and expecting it to fly like a DC-3. Finally, nobody is trying to explain why the ancestor of the birds must be a dinosaur with a lizard-like (saurischian) pelvis, rather than one of the many "bird-hipped" (ornithschian) species. If the evolutionary story is true, then we ought to tell the folks at the Smithsonian to remodel the National Air & Space Museum, because the Wright Brothers' airplane will have to take second place to the first airborne dinosaur!
As in the previous sections, we have here a situation where we are expected to accept on faith that one life form made a series of critical changes to become something different, because we don't have the fossil evidence to prove it. The feather is quite a complicated structure, with all kinds of hooks and barbs to keep itself rigid and lightweight at the same time. Supposedly it evolved from the simple flat scales of reptiles, but where's the transitional fossil?
I can now hear the evolutionist saying, "Aha, but we do have the transitional fossil; we have archaeopteryx!" The fossil we have of archaeopteryx shows a number of primitive features, including reptile-like teeth, claws on its wings, and a small breastbone (which means it was a poor flyer). Yet it also has fully developed feathers, and could fly, so even evolutionists concede it was a fully developed bird. As for the "primitive" features, I'll say just a few words about them.
1. The teeth aren't really that remarkable. True, there are no toothed birds today, but every other class of vertebrates comes in toothed and toothless forms. We have fish with teeth and fish with no teeth; reptiles with teeth and reptiles with no teeth (turtles); mammals with teeth and mammals without teeth (anteaters); people with teeth and people without teeth! Why couldn't God have created toothy birds at first, to fly with the toothless ones that are still with us today?
2. The claws on the wings aren't unique either. There are three species of birds today which possess claws: the hoatzin of South America, and the touraco and ostrich of Africa. None of them are good flyers (the ostrich doesn't fly at all); if they were extinct, and one of them was found as a fossil, the paleontologists might think this was a primitive "halfway bird."
3. The archaeopteryx fossil was dated to the Jurassic period, about 150 million years ago. Recently another fossil bird was found in a rock dated to be 75 million years older, and it looks even less like a reptile than archaeopteryx does. Since offspring cannot be the fathers of their parents, this means that archaeopteryx is not the missing link; now the paleontologists have to go look for another one. Meanwhile they have to use their imagination to fill the blanks (some textbooks sport a picture of a lizard with feathers called "pro-avis," and suggest that the ancestor of birds looked like this).
In 1999, the National Geographic Society announced the discovery of "feathered dinosaurs" in northeast China's Liaoning province. One fossil caused such a sensation that they dubbed it archaeoraptor ("ancient bird of prey") and rushed to publish an article about it, entitled "Feathers for T. rex? New birdlike fossils are missing links in dinosaur evolution." The article, which appeared in November 1999, was richly illustrated with speculations on what these feathered dinosaurs looked like, even suggesting that a baby tyrannosaurus had a coat of down like a duckling, only to shed it when it got big. Then the fossil went on public display in Washington D.C., while news reports, Internet sites and TV specials announced the find worldwide.
A few scientists challenged such claims immediately. Larry D. Martin, a paleontologist from the University of Kansas, argued that nobody could prove that the feather-like impressions in the rock surrounding the bones were really feathers, while Storrs L. Olson, the curator of birds at the Smithsonian, accused National Geographic of committing sensationalist tabloid journalism. This prompted one of Archaeoraptor's supporters, Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology (in Beijing, China), to go to Liaoning and check out the rock slab where it had been discovered. What he found was embarrassing; the Chinese farmer who lived on the property had dug up several pieces of fossils, and joined a bird's body with a dinosaur's tail to produce a specimen that was complete enough to be worth something. In other words, archaeoraptor was a hoax, much like one we'll look at in the next chapter--Piltdown Man.
This is as good a place as any to point out that there are many characteristics in animals that are so complicated, they would be useless if they appeared in a less than fully developed form. The wings of the bird and the pterodactyl, for instance. A good change in an organism's makeup is supposed to improve its chances for survival, but if some lizard was born with half-developed wings, what would it do with them? It could not fly with them, and they will probably keep it from running very fast. How will it catch its food or run away from its enemies? If it tried to fly with them--splat!--no more lizard. A creature with half-developed wings is worse off than one with no wings at all.
Likewise, how could the bombardier beetle's unique cannon evolve, if it would cook the beetle that tried to blast a predator before it was fully developed? How could any form of symbiosis (beneficial interaction between two life forms) develop? Flowers and bees cannot survive without each other, so which came first?(13) How could cleaner fishes like the wrasse survive if they tried to clean the mouth of a big fish that had not yet developed the instinct to let them work without eating them? What good would our eyes be if the cornea and lens evolved before the retina did? I could go on and on listing characteristics that show the work of intelligent design, rather than the chance acquisition of one characteristic at a time. I am reminded of what the naturalist William Paley (1743-1805) said about such ideas: "If the human eye came by chance, then so could the telescope!"
This is the End of Chapter 4.
FOOTNOTES
1. Velikovsky, Earth In Upheaval, Garden City, NY: Doubleday & Co., 1955, pg. 202.
2. Coffin, Harold G., Creation--Accident or Design?, Washington, D.C., Review & Herald Publishing Association, 1969, pgs. 73-74.
3. Ladd, Harry S., "Ecology, Paleontology and Stratigraphy," Science, Vol. 129, January 9, 1959, pg. 72.
4. Stokstad, Erik, "Tyrannosaurus rex Soft Tissue Raises Tantalizing Prospects," Science, Vol. 307, March 25, 2005, pg. 1852. For pictures, check out "Scientists recover T. rex soft tissue" at MSNBC.com.
5. Noorbergen, Rene, Secrets of the Lost Races, New York, The Bobbs-Merrill Company Inc., 1977, pg. 16.
6. Coffin, pg. 76.
7. Plug, plug.
8. "Time, Life and History in the Light of 15,000 Radio Carbon Dates," The Creation Research Society Quarterly, June 1970, pgs. 56-59.
9. Journal of Geophysical Research, Vol. 73/14, July 15, 1968.
10. L. Hallonquist, Radio-Active Dating, pg. 2; and Science Journal, November, 1968.
11. Gish, Duane T., "Dating of the Moon Rocks," Creation Science Report, Vol. 1, No. 2, March/April 1972.
12. L. Hallonquist, The Age of the Earth, pgs. 4 and 5.
13. My favorite example of symbiosis is similar to the flower and the bee; the relationship between the calimyrna fig and the fig wasp. There are many steps involved in that relationship, and if any of them didn't work out, both the fig and the fig wasp would have become extinct by now. For a start, the fig has the most unusual structure of any fruit I have ever seen; the flowers are on the inside of the fruit, instead of the outside. And unlike most plants, figs come in sexes, with male and female flowers on different plants, so if it wasn't for the fig wasp, which is tiny enough to get inside the fig, pollination of those flowers would be impossible. For those who are unfamiliar with the relationship, check out the Calimyrna Figs in California page to read the whole story, and the next time you eat a fig, remember that it's the life work of an insect the size of a gnat. I dare anyone to show me how all that could happen without intelligent design!
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Greens
Active member
Sam_Skunkman said:
Really, I don't see why it is confusing in any way to consider anandamide, which is clearly an endocannabinoid, a cannabinoid. To me and to most modern scientists studying cannabinoids, it is much more confusing to say that it is not one. I mean, how many times do I have to say that endocannabinoid means a cannabinoid produced by the animal body? However, like I said before, it is really just a matter of semantics. It just depends on how you define the word "cannabinoid". After all, "cannabinoid" is just a word made up by humans to describe certain compounds.
As for CBD, doesn't it have an affect on the CB receptors. Doesn't it actually bind to the receptor, blocking out other cannabinoids such as THC?
