By Amy Norton Source: Reuters In findings that could one day offer an alternative to so-called medical marijuana, scientists have discovered that blocking a particular enzyme in mice allows a natural marijuana-like compound in the brain to trigger pain-numbing effects comparable to the drugs. Researchers have known that the brain chemical anandamide acts on the same brain receptors as marijuana does. Anandamide is known as an endogenous cannabinoid, a class of marijuana-like compounds that naturally exist in the body. What has been unclear is why injecting anandamide into the body does not have the same medicinal effects that marijuana reportedly has. "It can't accumulate and hang around like THC (marijuana's active ingredient)," Benjamin F. Cravatt of The Scripps Research Institute in La Jolla, California, explained in an interview. Cravatt and his colleagues hypothesized that an enzyme called FAAH--for fatty acid amide hydrolase--quickly breaks down extra anandamide in the brain before it can trigger marijuana-like effects. They confirmed this belief in experiments with mice engineered to lack the FAAH enzyme. When these FAAH-less animals were exposed to various doses of anandamide, they showed effects similar to those that have been seen in mice treated with THC, Cravatt explained. For one, the mice became lazy and less responsive. More importantly, they became less sensitive to pain, according to the report in the July 31st issue of the Proceedings of the National Academy of Sciences. These findings, Cravatt said, hold out the possibility that a drug that blocks the FAAH enzyme in humans will allow the natural anandamide system to work as a painkiller--but without making patients inhale the toxic compounds in marijuana smoke or experience the drug's mind-altering effects. He noted that he and his colleagues will also look at whether mice lacking the FAAH enzyme show changed eating patterns. Advocates of medical marijuana use say that in addition to easing the chronic pain of cancer and other conditions, the drug helps prevent AIDS-linked wasting by stimulating patients' appetites. A drug that blocks FAAH in the brain would likely be more desirable than either marijuana smoking or the synthetic cannabinoids now available for chronic pain control, Cravatt suggested. It would get around the ill effects of smoking and probably be more effective than introducing a foreign cannabinoid because it would boost the body's natural cannabinoid system. "Ideally," Cravatt said, "what you want is to allow the endogenous system to be enhanced." Source: Proceedings of the National Academy of Sciences 2001;98:9371 Source: Reuters Health (NY) Author: Amy Norton Published: July 23, 2001 Copyright: 2001 Reuters Health