Nerve Receptor Tied to Cannabis and Opiate Abuse 

Nerve Receptor Tied to Cannabis and Opiate Abuse 
Posted by FoM on January 15, 1999 at 17:15:10 PT

Nerve Receptor Tied to Cannabis and Opiate Abuse! NEW YORK A receptor found on the surface of nerve cells in the areas of the brain that are tied to addiction may control responses to both Marijuana and Heroin, according to the results of studies in mice.
Drugs aimed at "switching off" the receptor might "be considered for preventing the development of dependence on opiates and possibly other addictive drugs," conclude a team of European researchers led by Dr. Catherine Ledant of the Universit libre de Bruxelles in Brussels, Belgium. Their findings are published in the Jan. 15 issue of the journal Science.The authors point out that chemicals found in marijuana smoke bind to the receptor, called CB1, and this type of receptor "is abundant in the (cells of) central and peripheral nervous systems."To determine the role this receptor might play in marijuana dependence, the researchers genetically engineered a line of 'knockout' mice born without functioning CB1.They report that normal mice quickly began to display "high" and addictive behaviors after exposure to THC, a chemical found in marijuana. But the knockout mice who lacked functioning CB1 receptors seemed unaffected by, and disinterested in, administration of THC."These results demonstrate that the main pharmacological responses to (THC), as well as the addictive properties of cannabinoids, are indeed mediated mostly, if not exclusively, by the CB1 receptor," the authors conclude.In a second experiment, the investigators exposed knockout mice to morphine, one of the opiate family of drugs that includes heroin.Both normal and knockout mice showed typical 'drugged' responses to morphine. However, mice without working CB1 receptors seemed much less eager to self-administer the drug (via poking a lever with their nose) compared with normal mice. According to the authors, this suggests "that CB1 receptors are required for the development of physical dependence" on opiates.If the results of the mouse study are duplicated in human trials, the CB1 receptor could present researchers with a "two-in-one" target for new anti-addiction drug therapies, Ledant's team speculates. 
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