The Relationship between Social Reward Behavior and Mesolimbic Dopamine Release.

Deficits in social behavior, such as reduced motivation and social avoidance, are key symptoms in several psychiatric disorders. Distinct modes of reward, such as drug and social, may rely on different dopamine release patterns in the mesolimbic pathway. We investigated the relationship between social reward behaviors and dopamine release elicited by phasic and tonic stimulation patterns in C57BL/6J mice. Social conditioned place preference was used to assess motivation for social interaction, and in vivo fixed potential amperometry was used to measure nucleus accumbens dopamine release before and after cocaine (10 mg/kg, ip). Additional measures included the frequency and duration of social interactions during conditioning sessions, with the first and last session representing novel and familiar social interactions respectively. No relationship was found between baseline (pre-cocaine) dopamine and social place preference in either sex. However, in males, social place preference negatively correlated with cocaine-induced phasic dopamine release, indicating that increased social motivation was associated with a reduced phasic dopaminergic response to cocaine. In contrast, greater novel interaction was associated with increased baseline dopamine elicited by tonic stimulations. These relationships were not observed in females. Overall, these findings suggest distinct, sex-dependent roles for phasic and tonic dopamine release in mediating social reward.