Standing strong: Effects of social dominance on neural activity and defeat-induced social avoidance in female Syrian hamsters.

Social dominance modulates stress vulnerability, yet the neural mechanisms by which dominance status alters responses to stress in females remain poorly understood. This study aimed to determine whether activation of neurons in the posterior medial amygdala (MeP) and ventral medial prefrontal cortex (vmPFC) was associated with reduced stress vulnerability in dominant female Syrian hamsters. We created dominance relationships in hamsters, exposed animals to social defeat stress, tested animals for stress-induced social avoidant responses, and collected tissue for c-Fos immunohistochemistry. Dominant females showed a significantly longer latency to submit during social defeat exposure compared to subordinates, accompanied by elevated c-Fos expression in the infralimbic (IL) and prelimbic (PL) cortex. In addition, dominant females showed greater social interaction in a social avoidance (SA) test compared to subordinates, suggesting resistance to a stress-induced loss of social motivation. Nevertheless, dominant and subordinate hamsters did not differ in c-Fos expression in MeP, IL, or PL neurons during SA testing. These findings suggest that reduced activity of PL and IL neurons during social defeat exposure leads to stress vulnerability in female hamsters and are consistent with the idea that vmPFC activity during stressful experiences enables stress resistance. Delineating the mechanisms by which social dominance alters vmPFC activity in females could have broad implications for understanding sex differences in risk for stress-related disorders, including post-traumatic stress disorder.