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Why it's hard to quit smoking LONDON (May 7, 1998 00:44 a.m. EDT http://www.nando.net) - Smoking may be such a difficult habit to break because nicotine withdrawal decreases the brain's ability to experience pleasure, scientists reported Wednesday. Every smoker who has ever tried to stop knows about the physical symptoms, but researchers at The Scripps Research Institute in La Jolla, Calif., found that nicotine addiction also involves dramatic changes in the brain's pleasure circuits. "Understanding these decreases in the brain's sensitivity to pleasurable stimulation that occur during nicotine abstinence helps explain why it is so hard for people to stop smoking," Dr. Alan Leshner, the director of the U.S. National Institute on Drug Abuse which funded the research, said in a statement. "This understanding may also help in the development of better treatments to address withdrawal symptoms - depression, anxiety, irritability and craving - that interfere with people's attempts to quit smoking." Dr. Athina Markou and a team of researchers used rats to measure brain sensitivity to pleasurable electrical stimulation. Their research was published in the scientific journal Nature . The scientists measured pleasurable electrical pulses associated with the hypothalamus area of the brain. The rats administered the pulses to themselves both before and after being given nicotine. During a week when the rats had the nicotine equivalent of smoking one and a half packs of cigarettes a day there was no change in the electrical pulse they gave themselves. But when the nicotine was withdrawn, the intensities of the electrical circuits had to be increased by more than 40 percent before the rats found them enjoyable. "These results are comparable to the altered brain reward sensitivity found also during withdrawal from many other addictive drugs," said Markou. "The results of this research indicate that we have a good animal model to study the neurobiology of nicotine abstinence and thus assist in the development of behavioral and pharmacological treatments for nicotine addiction." Medical experts say smoking is a major preventable cause of death throughout the world. More than half a million European die from smoking related diseases every year. Many smokers who do not die from the habit develop debilitating diseases such as chronic bronchitis, emphysema and cardiovascular disease. Copyright 1998 Nando.net Copyright 1998 Reuters News Service janet paterson 51/10 - sinemet/selegiline/prozac almonte/ontario/canada - [log in to unmask]