SOCIAL STATUS MODULATES RESTRAINT- INDUCED NEURAL ACTIVITY IN BRAIN REGIONS CONTROLLING STRESS VULNERABILITY 

Understanding the cellular mechanisms that control resistance and vulnerability to stress is an important step toward identifying novel targets for the prevention and treatment of stress-related mental illness. Dominant and subordinate animals have been shown to exhibit different behavioral and physiological responses to stress, with dominants often showing stress resistance and subordinates often showing stress vulnerability. We have previously found that dominant hamsters exhibit reduced social avoidance following social defeat stress compared to subordinate hamsters, although the extent to which stress resistance in dominants generalizes to non-social stressors is unknown. In this study, dominant, subordinate, and control male Syrian hamsters were exposed to acute restraint stress for 30 minutes. Brains were collected 60 minutes following restraint stress to quantify the number of c-Fos immunopositive cells in brain regions associated with stress-related behavior. Dominants and subordinates did not significantly differ in c-Fos immunoreactivity within subregions of the dorsal raphe nucleus or the paraventricular nucleus of the hypothalamus. However, compared to dominants and controls, subordinates displayed less restraint-induced c-Fos immunoreactivity in the infralimibic and prelimbic cortices. A similar trend was found in the ventral medial amygdala. These data are consistent with the reduced forebrain neural activity exhibited by subordinates following social defeat stress and suggest that subordinates exhibit a pattern of restraint-induced neural activity characteristic of stress vulnerability. However, dominant animals did not show restraint-induced changes in c- Fos immunoreactivity, suggesting that the cellular mechanisms controlling resistance to social defeat stress may not generalize to physical restraint.