Common mechanisms of reinforcement from alcohol and other drugs

Vulnerability to substance abuse is an important social and scientific issue. A critical aspect of this phenomenon is the degree to which individuals who abuse one substance are likely to abuse other substances. The extent to which several pharmacologically distinct drugs will come to serve as positive reinforcers within genetically defined subjects defines their community with respect to abuse liability. Questions in this area are directed at determining whether reinforcement from and abuse of alcohol and other drugs define variations within a single behavioral phenomenon, or whether reinforcement and abuse must be individually defined for each substance involved. Previous studies have shown that ethanol can be readily established as a positive reinforcer in LEWIS rats and C57BL/6J mice. In low ethanol preferring F344 rats, ethanol maintains significant but low levels of responding. Ethanol does not maintain behavior in BALB/cJ or DBA/2J mice. These genotypic patterns of reinforcement from ethanol appear to correlate highly with patterns of reinforcement from cocaine and opiates. Other studies suggest that some aspects of drug self-administration may be mediated in part by common dopaminergic and serotonergic mechanisms, and animals which differ in ethanol drinking behavior show substantial differences in parameters of serotonergic function. Thus, there may exist important genetic determinants of drug reinforced behavior.