Prior studies offer strong evidence that rs12364283 is a functional polymorphism. Those with a copy of the minor (G) allele have significantly greater DRD2 expression (Zhang et al., 2007). Minor allele carriers have been reported to differ significantly in their performance on behavioral tasks pertinent to PTSD (Frank and Hutchison, 2009; Hamidovic et al., 2009). On a probabilistic selection reinforcement learning task, rs12364283 G allele heterozygotes demonstrated an intact ability to select a stimulus that was previously highly reinforced (Frank and Hutchison, 2009); however, they were significantly less likely to refrain from choosing a stimulus that was previously less reinforced. Some trauma exposure (e.g., natural disaster) is unavoidable; deficits in avoidance learning would likely increase risk for other forms (i.e., involving components of repeated risk-taking). Another report (Hamidovic et al., 2009) noted that young adults heterozygous for the rs12364283 G allele had lower levels of self-reported impulsivity and significantly faster stop signal reaction times on a behavioral inhibition task. Administration of d-amphetamine improved stop signal reaction times at all doses in non-carriers of the rs12364283 G allele. In contrast, the stop signal reaction times of G allele heterozygotes worsened at all doses (significantly so at the 10mg dose).
