Variation in DRD2 has been investigated in relation to amphetamine-induced impulsive behavior. Amphetamine increases behavioral inhibition, and the degree of this inhibition varies across individuals (de Wit et al. 2000). We examined the role of several SNP polymorphisms in DRD2 and the effects of amphetamine on behavioral inhibition utilizing the sample of healthy human subjects that is described above. Individuals were phenotyped with the stop task (Logan et al. 1984), a measure of behavioral inhibition, and genotyped at 12 SNPs in DRD2 (but not the Taq1A polymorphism). One SNP, rs12364283, was significantly associated with better performance on the stop task following 10 mg amphetamine administration in the G/G and A/G groups. This G allele of this SNP, as discussed earlier, is associated with increased DRD2 expression (Zhang et al. 2007); increased DRD2 expression may be related to better task performance (Cropley et al. 2006).
