Functional Characterization of Dopamine Projections Across Nucleus Accumbens Subregions in Reward-related, Anxiety-like and Locomotor Behaviors

Mesolimbic dopamine (DA) neurons projecting to the nucleus accumbens (NAc) have traditionally been viewed as a functionally homogeneous reward pathway. However, recent evidence reveals functional heterogeneity, with DA projections to specific NAc subregions responding not only to rewards but also to aversive and safety-related stimuli. The extent to which DA projections across distinct NAc subregions differentially promote reward, aversion and anxiety-related behavior remains incompletely understood. To address this question, we performed optogenetic inhibition of DA terminals across different NAc subregions during real-time place preference and anxiety-related tests in predominantly male mice. We found that inhibition of DA terminals across all NAc subregions produced robust place avoidance, indicating that DA input to each subregion is similarly reinforcing and that its inhibition is aversive. In contrast, DA terminal inhibition resulted in subregion-specific effects on locomotor activity but had no acute effect on anxiety-like behavior. Together, these findings suggest that while DA projections to the NAc are uniformly reinforcing, they exhibit subregion-specific roles in regulating locomotor activity and have no acute effect in modulating anxiety, highlighting both common and diverging functions of distinct mesolimbic DA systems. Significance statement Mesolimbic dopamine system projecting to the nucleus accumbens (NAc) is associated with reward, motivation, aversion and regulation of affective states. However, the functional contribution of projection-specific dopamine input to distinct NAc subregions is incompletely understood. Using optogenetic inhibition of dopamine terminals across NAc subregions, we show that dopamine input to each subregion uniformly promotes reward, as its suppression induces place avoidance. Conversely, dopamine terminal inhibition produces subregion-specific effects on movement and does not acutely affect anxiety-like behavior. These findings reveal that the mesolimbic dopamine projections share a common role in promoting reward but differ in their contributions to motor regulation. Our results provide important insights into functional architecture of the mesolimbic dopamine system, with important clinical implications for reward-related disorders.