Monetary discounting and ventral striatal dopamine receptor availability in nontreatment-seeking alcoholics and social drinkers

Rationale Dopamine (DA) in the ventral striatum (VST) has long been implicated in addiction pathologies, yet its role in temporal decision-making is not well-understood. Objectives To determine if VST DA D 2 receptor availability corresponds with greater impulsive choice in both nontreatment-seeking alcoholics (NTS) and social drinkers (SD). Methods NTS subjects ( n = 10) and SD ( n = 13) received PET scans at baseline with the D 2 /D 3 radioligand [ 11 C]raclopride (RAC). Outside the scanner, subjects performed a delay discounting procedure with monetary rewards. RAC binding potential (BP ND ) was estimated voxelwise, and correlations were performed to test for relationships between VST BP ND and delay discounting performance. Self-reported impulsivity was also tested for correlations with BP ND . Results Across all subjects, greater impulsive choice for $20 correlated with lower BP ND in the right VST. NTS showed greater impulsive choice than SD and were more impulsive by self-report. Across all subjects, the capacity of larger rewards to reduce impulsive choice (the magnitude effect) correlated negatively ( p = 0.028) with problematic alcohol use (AUDIT) scores. Self-reported impulsivity did not correlate with BP ND in VST. Conclusions Preference for immediate reinforcement may reflect greater endogenous striatal DA or lower D 2 number, or both. Alcoholic status did not mediate significant effects on VST BP ND , suggesting minimal effects from alcohol exposure. The apparent lack of BP ND correlation with self-reported impulsivity highlights the need for objective behavioral assays in the study of the neurochemical substrates of behavior. Finally, our results suggest that the magnitude effect may be more sensitive to alcohol-induced problems than single discounting measures.