From - Fri May 29 00:26:39 1998

HT: Researcher explores brain's own marijuana-like substance

Research into cannabinoid provides evidence that the use of marijuana to treat pain and nausea should not be so easily dismissed

[1]By Richard P. Morin

The legalization of marijuana for medical purposes, already on the books in Florida and Ohio and approved by voters in Arizona and California, has been labeled by the Clinton administration as a cruel hoax. J. Michael Walker, professor of psychology and neuroscience, disagrees. Research into the human body's own naturally-occurring marijuana-like substance, known as cannabinoid, provides evidence that the use of marijuana to treat pain and nausea should not be so easily dismissed, Walker said. "Politicians have played political football with the issue," said Walker, who believes further research into the medicinal uses of marijuana is necessary before any final judgment can be made. Walker's own research focuses on the body's use of cannabinoid, an endogenous substance that mimics the behavior of the psychoactive compound in marijuana - Delta 9 tetrahydrocannabinol (THC). The high concentration of cannabinoid receptors in the brain suggests that these marijuana-like substances are part of a major neurochemical system in the brain, write Walker and colleagues in the Oct. 15th issue of the Journal of Neuroscience. How that neurochemical system definitively works is unknown. But research by Walker has shown that cannabinoids and their receptors are used in some way to modulate pain in the human body. In laboratory tests, Walker and colleagues have administered mildly painful stimuli to lab rats and recorded their responses. They found that the administration of a synthetic compound that behaves like marijuana and stimulates cannabinoid receptors reduced these responses. Moreover, the reactions of nerve cells in the brain and spinal cord that transmit pain messages to the body became less responsive to the pain-evoking stimuli. Walker said the particular role of the brain's own marijuana-like substance as a pain inhibitor was suggested by experiments in which a drug was given to block the action of marijuana. During laboratory tests, the marijuana-blocking drug caused rats to show increased sensitivity to pain. A similar result was found in an experiment in which animals received electrical stimulation in an area of the brain thought to contain naturally-occurring marijuana-like substances. The electrical stimulation produced a state of insensitivity to pain in rats. This effect was diminished by the marijuana-blocking drug. Walker concluded that this experiment appears to show electrical stimulation caused the release of a marijuana-like drug from the brain, which acted as a natural painkiller. "Under natural circumstances these cannabinoids are reaching the cells and keeping pain in check," he said. Scientists have known for many years that the human body also uses a morphine-like substance to dampen pain. Some scientists believe marijuana may be an even more effective painkiller because the level of cannabinoid receptors in the spinal cord is 10 to 50 times higher than that of opiate receptors which respond to such legal painkillers as morphine. There is a historical precedent for the use of marijuana as a painkiller as well. At the turn of the century, hemp extracts "were available in virtually every pharmacy in the United States," said Walker. "When the syringe was invented, there was a great preference for using morphine, because these opiates were quite soluble in water. The active substance in marijuana was not." Soon after the development of the syringe, marijuana fell out of favor with physicians. It was subsequently outlawed and associated with the ills of society. But Walker said there is an irony to the federal government's condemnation of smoking marijuana as a treatment for pain and nausea: Marinol - a pill form of Delta 9 THC, the psychoactive compound in marijuana - is a federally-approved drug. Research has shown that smoking marijuana allows a faster, more controllable method of ingestion. "Marinol, the pill form, is not absorbed evenly or quickly, which creates problems because the ideal dose range is very narrow," said Walker. "If a patient receives too little, there is no effect, and if he or she receives too much, there is a tendency to have adverse reactions such as confusion and anxiety." Although smoking marijuana can contribute to lung damage and may lead to the use of other drugs with no medical value, "other drugs that are used medicinally also are abused, such as morphine," Walker said. "There is no logic to the idea that because a drug is abused means it has no medicinal value, as is sometimes implied for marijuana. I hope to see more and better research on the therapeutic potential of this important class of compounds." References 1. --UAA25856.896413242/