Go back to the Index


In 1990 Israeli scientists discovered 'receptors' in the human brain which are uniquely suited for cannabis. In 1992 a special protein binder was identified.

Cannabis acts on specific cannabinoid receptors in the brain. Such receptors have been found in humans, in rats, chickens, turtles, trout and possibly even in fruit flies.

This distribution may suggest that the gene responsible must have been present early in evolution, and its conservation implies that the receptor serves an important biological function.

Since THC is not a naturally occurring substance within the brain, the existence of a cannabinoid receptor implied the existence of a naturally occurring or 'endogenous' cannabinoid-like substance. A brain molecule which binds to the receptor was identified (by Devan in 1992). The molecule is called arachidnylethanolamide and is fat soluble like THC. It has been called anandamide from the Sanskrit word meaning bliss' This substance has no effect on cells which do not have the receptor. The biological role of the anandamide molecules remain unknown. (Above extracted from Australian Government Report)

The action of cannabis in the brain is completely different to the actions of hard drugs. The latter effect levels of a chemical called dopamine which occurs naturally in the brain. This is the chemical which enables us to feel pleasure. Heroin and cocaine and derivatives repress the production of dopamine. The pleasure or high of the drug is caused by artificially boosting the pleasure centres. When the drug wears off the natural dopamine production is lowered and the user wants more drug. This is particularly true of cocaine where the high is short lived. A snort of cocaine usually makes one want another line soon. Long term use of hard drugs has a more disastrous effect and abstinence produces withdrawal symptoms, the user often unable to feel any pleasure at all.

Many people who use cannabis think they simply do so for the buzz. In fact cannabis is not only a medicine which makes people well, it is also a preventative medicine. Some people seem miserable or even angry when their supply of cannabis runs out; this is because that is how they used to be before taking cannabis.

A very few people have allergic reactions to cannabis. Some of these are to grass and not to hash. Even fewer people have negative metal effects - sometimes wrongly called 'cannabis psychosis'. These reports are complicated because the person has sometimes consumed other substances such as cocaine or LSD at the same time as cannabis or in the past and have not reported it to their doctor, so cannabis gets the blame. Other complications are the impurities in the cannabis and a possibly unbalanced mind to start with.


TAMPA, Fla., June 9 /PRNewswire/ --
In Dr. Thomas Klein's crowded laboratory office, beneath the shelves of scientific journals hangs a preserved puffer fish with an imitation joint dangling from its mouth.

Even the ancient blowfish has been found to harbor chemical receptors that react to delta-9 tetrahydrocannabinol, or THC, the compound in marijuana that produces a high said Dr. Klein, professor of medical microbiology and immunology at the University of South Florida.

"It's fascinating," he said. "Why would both humans and this fish evolve with the genes for a receptor that would only be activated if you smoked marijuana? Conservation through evolution suggests that the gene is important.

"We now know there's a substance circulating in the body called anandamide that binds to cannabinoid receptors. So there's definitely a physiological role for endogenous cannabinoid receptors, possibly in behavior modification or defining moods as well as regulating immunity and other functions."

Dr. Klein is a pioneer in the new field of psychoneuroimmununology. He studies physical links between drugs of abuse and the brain, emotions and immunity.

Supported by a $674,000 National Institutes of Health grant, he heads one of few scientific groups in the world investigating the function of cannabinoid (marijuana) receptors in the immune system. Cannabinoid receptors have also been found in the brain, the gut and the reproductive system.

Cells imbedded with these receptors are inhibited from functioning when exposed to the THC molecule.

Pot's influence on the immune system continues to be hotly debated within the medical community. Animal and human studies have demonstrated that virtually every immune function, from antibody production to the destruction of invading microorganisms, is suppressed by relatively high concentrations of marijuana. In those whose immune responses are already poor, marijuana may aggravate deteriorating health.

"It's believed to be a rather benign drug, effective in reducing pain and nausea," Dr. Klein said, "but scientific evidence is accumulating, through the study of the cannabinoid receptor system, that THC might affect almost every cell in the body.

"People need to know that if they smoke marijuana, they are not just altering their moods. They're altering their immune systems."

Scientists may know more about marijuana's hazards or benefits to health once they understand how the cannabinoid system fits into the body's complex network of immune regulation.

Dr. Klein suspects the natural purpose of cannabinoid receptors may be to control more powerful immune systems serving as the body's first line of defense against infection or tumors.

"The horse gets the buggy started, but the cannabinoid system is like the driver with the whip who keeps things going," he said.


From : Business Week, November 4, 1996, Pg. 199

The first drug to curtail the spread of brain damage resulting from strokes and head or spinal cord injuries has entered clinical tests at six hospitals in Israel. Its key ingredient is dexanabinol, a synthetic molecule based on the active agent in marijuana. Dexanabinol was discovered six years ago by Raphael Mechoullam, a researcher at Hebrew University in Jerusalem, and developed by the Rehovot (Israel) research arm of Pharmos Corp. in Alachua, Fla.

Dexanabinol has two novel properties: It can cross the so-called blood-brain barrier that prevents foreign molecules from entering the brain. And once in, the drug appears to halt the brain-cell deterioration that follows a blow to the head or a stroke. In four years of animal testing, the drug produced "outstanding" results, says Michael Schickler, vice-president of Pharmos' Israel operations. Pharmos expects clinical tests to be completed by the end of 1997. If it works, dexanabinol could hit the market by 2000.


The Coptic Study of 1981 stated:
...I.Q.'s of Zion Coptics increased after they began to use ganga

CANNABIS AND THE BRAIN: Iversen, L, Brain. 2003; 126: pp. 1252-1270. A large literature exists on the effects of cannabis,this review focuses mainly on the more recent literature in this field.



Does Marijuana Use Cause Long-Term Cognitive Deficits?: Four letters in the Journal of the American Medical Association, 22 May 2002