Vulnerability to substance abuse is an important emerging issue. Some related factors are the relationship between propensity to self-administer a drug and neurosensitivity to that drug; similarities and differences between various models of drug seeking behavior; and the commonality of drug-seeking behavior across drugs and genotypes, that is, 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. 2. Findings related to these issues are now being obtained from the areas of pharmacogenetics and operant drug self-administration. 3. The results indicate that reinforcement from alcohol and other drugs is only moderately related to preference for alcohol and other drugs. In addition, neurosensitivity to drugs appears to have little influence on whether that drug will come to serve as a positive reinforcer for any given individual or animal. Indeed, the critical factor appears to be the individual organism's innate propensity to find a particular drug reinforcing. 4. Initial findings also show that genotypic patterns of reinforcement from ethanol appear to correlate highly with patterns of reinforcement from cocaine and opiates. 5. From these findings it is concluded that there exist important genetic determinants of drug reinforced behavior; reinforcement is an important and independent effect of several psychoactive drugs; and drug seeking behaviors maintained by ethanol, cocaine and opiates may have at least some common biological determinants.
