Sexually dimorphic oxytocin circuits drive intragroup social conflict and aggression in wild house mice

In nature, both males and females engage in competitive aggressive interactions to resolve social conflicts, yet the behavioral principles guiding such interactions and their underlying neural mechanisms remain poorly understood. Through circuit manipulations in wild mice, we unveil oxytocin-expressing (OT+) neurons in the hypothalamic paraventricular nucleus (PVN) as a neural hub governing behavior in dyadic and intragroup social conflicts, influencing the degree of behavioral sexual dimorphism. We demonstrate that OT+ PVN neurons are essential and sufficient in promoting aggression and dominance hierarchies, predominantly in females. Furthermore, pharmacogenetic activation of these neurons induces a change in the ‘personality’ traits of the mice within groups, in a sex-dependent manner. Finally, we identify an innervation from these OT neurons to the ventral tegmental area that drives dyadic aggression, in a sex-specific manner. Our data suggest that competitive aggression in naturalistic settings is mediated by a sexually dimorphic OT network connected with reward-related circuitry. In nature, female mice, like males, display aggression and dominant hierarchy. This study in wild mice identifies oxytocin-expressing neurons as a hub governing these behaviors, influencing the degree of sexual dimorphism in social conflicts.