Sex-Dependent Differences in Nucleus Accumbens Regulation of Aggression and Social Investigation

Throughout the animal kingdom, dominance relationships establish stable hierarchies that are important for regulating access to limited resources, such as food, territory, and mates (Yan et al., 2024). Formation of these structured relationships requires shifts in aggressive and submissive behavior among individuals and is highly adaptive because these hierarchies allow animals to avoid conflict and conserve energy. Experience-dependent changes in behavior often occur through a process of positive reinforcement, and winning aggressive encounters is known to be rewarding. The nucleus accumbens (NAc) is a key structure in the mesolimbic dopamine system that regulates reinforcement learning, motivation, and reward processing. It contains a high density of dopamine-receptor-expressing neurons that receive input from several limbic and cortical regions, including the ventral tegmental area (VTA) and the medial prefrontal cortex (mPFC; Xu et al., 2024). The NAc plays a critical role in the rewarding aspects of aggression, as demonstrated through conditioned place preference assays in mice (Golden et al., 2016). Also, the positive reinforcing effects of aggression in hamsters are associated with phasic increases in dopamine in the NAc core (Cross et al., 2025). Nevertheless, much remains unknown about the cellular mechanisms and neural circuitry in the NAc regulating behavioral plasticity after repeated aggressive encounters. Borland et al. (2026) investigated how NAc activity regulates experience-dependent changes in aggression and social investigation. Investigating aggression in traditional rodent models can be challenging because female mice and rats do not consistently display robust aggressive behavior under standard housing conditions. In contrast, both male and female Syrian hamsters readily exhibit territorial aggression, making them a valuable model for investigating sex differences in the neurobiological mechanisms underlying changes in aggression. Initial investigations evaluated whether repeated social interactions produce behavioral changes and alter activity of NAc neurons in male and female Syrian hamsters. Behavioral testing consisted of four social … Correspondence should be addressed to Jessica T. Tremblay at jtrembl4{at}vols.utk.edu.