Source: International Herald Tribune June 28, 1996 Contact: Addled? Could Be the Marijuana Heavy Use Might Prime the Brain for Other Addictions By Sandra Blakeslee New York Times Service NEW YORK People who regularly smoke large amounts of marijuana may experience changes in their brain chemistry that are identical to changes seen in the brains of people who abuse heroin, cocaine, amphetamines, nicotine and alcohol scientists have found. The findings, based on studies of rats, were published Friday in the journal Science. They provide strong support for the emerging idea that all addictive drugs corrupt the same brain circuits, although to varying degrees, and suggest that chronic marijuana use may literally prime the brain for other drugs of abuse, a notion known as "the gateway effect." While the studies were conducted on rats, researchers are confident that the find ings will apply to humans virtually all of the biological mechanisms known to cause drug addiction were discovered in animal models before being established in humans. People who oppose the legalization of marijuana will be happy about these findings, while those who feel that marijuana is a benign drug will probably be upset, said Dr. Alan Leshner, director of the National Institute on Drug Abuse in Rockville Maryland, which financed the research. According to this new hypothesis, addictive drugs like nicotine heroin and cocaine all work through common pathways in the brain. One pathway is responsible for feelings of reward, and a second pathway underlies feelings of anxiety brought on by stress. In street drug parlance, one system produces the "high" while the other produces withdrawal. But many people thought marijuana was different because overt feelings of withdrawal are uncommon, said Dr. George Koob, a pharmacologist at the Scripps Research Institute in San Diego. The reason is that marijuana's active ingredient THC has a long halflifemeaning it lingers in the bloodstreamwhich in turn prevents the abrupt withdrawal symptoms seen in fastacting drugs like nicotine, he said.