New perspectives on cocaine addiction: recent findings from animal research.

Research with laboratory animals has provided several insights into the nature of cocaine abuse and addiction. First, the nature of drug addiction has been reevaluated and the emphasis has shifted from physical dependence to compulsive drug-taking behavior. Second, animal studies suggest that cocaine is at least as addictive as heroin and possibly even more addictive. Third, cocaine is potentially more dangerous than heroin as evidenced by the higher fatality rate seen in laboratory animals given unlimited access to these drugs. Fourth, the neural basis of cocaine reinforcement has been identified and involves an enhancement of dopaminergic neurotransmission in the ventral tegmental dopamine system. Other addictive drugs (e.g., opiates) may also derive at least part of their reinforcing impact by pharmacologically activating this reward system. Fifth, although the biological consequences of repeated cocaine self-administration on central nervous system functioning are poorly understood, preliminary findings suggest that intravenous cocaine self-administration may decrease neural functioning in this brain reward system. This has important clinical implications because diminished functioning of an important brain reward system may significantly contribute to relapse into cocaine addiction. These and other findings from experimentation with laboratory animals suggest new considerations for the etiology and treatment of drug addiction.