Dopaminergic neurons in the dorsal raphe nucleus may modulate social dominance in mice

Social hierarchies are central to the organizational structure of group-living species, shaping individual physiology, behavior, and social interactions. Dopaminergic (DA) systems, particularly within the ventral tegmental area (VTA) and dorsal raphe nucleus (DR), have been linked to motivation and competitive behaviors, yet their region-specific contributions to social dominance remain insufficiently defined. This study investigated the role of VTA and DR DA neurons in regulating social dominance in sexually naïve male C57BL/6J mice. Stable hierarchies were established using the tube test, after which both dominant and subordinate mice exhibited elevated c-Fos expression within the VTA and DR. Notably, dominant mice displayed significantly greater c-Fos activation in DR DA neurons compared to subordinates. Fiber photometry revealed that DA neurons in both regions were activated during proactive push behaviors and inhibited during passive retreats, with DR neurons showing stronger activation during dominance-related actions. Chemogenetic inhibition of DR DA neurons in dominant mice reduced their social rank, whereas activation in subordinates elevated their rank. In contrast, chemogenetic modulation of VTA DA neurons had no significant effect on social dominance. Manipulation of DA neurons in both regions produced rank-dependent changes in specific anxiety-like behavioral phenotypes. These findings highlight the distinct roles of DR and VTA DA neurons in social hierarchy regulation, identifying DR DA neurons as a critical component in the modulation of social dominance.