Endorphins and experimental addiction.
Animal studies suggest that the endogenous opioid systems in the brain play an important role in the initiation and maintenance of drug dependence. Opioids in the ventral tegmental area (VTA) may be involved in rewarded behaviors and, consequently, in the initiation of drug self-administration that may be associated with addiction proneness. Opioids in the limbic forebrain are particularly implicated in subsequent drug self-administration, which may be associated with craving, maintenance, and relapse. Alcohol intake in monkeys is reduced after treatment with naltrexone in a graded, dose-dependent manner. Naltrexone also is associated with a greater decrease in alcohol consumption after imposed abstinence. These findings support the idea that endorphins play a role in alcohol-drinking behavior, particularly after a period of abstinence during the so-called catch-up phenomenon. Recent studies of recovering alcoholic patients provide evidence that opiate antagonists attenuate the craving for alcohol and decrease and/or postpone relapse into addictive behavior.