An important aspect of these findings is the specific nature of the observed genotype group differences. OPRM1 effects were selective for the positive and rewarding effects of alcohol, as compared to the sedative and unpleasant effects, as this polymorphism putatively mediates alcohol-induced dopamine release in the striatum (Ramchandani et al., 2011). In a previous alcohol administration study, a factor analysisof subjective responses to alcohol found that Stimulation, Vigor, and Positive Mood loaded into a common ‘Positive Reinforcing’ factor, with separate ‘Negative Reinforcement’ and ‘Punishment’ factors (Ray et al., 2009). These results help further refine the literature by suggesting that the OPRM1 effects may be specific to alcohol reward and that these effects, both behavioral and genotypic, are present in alcohol dependent samples.
