The role of CRF in individual differences in response to social defeat: neuroendocrine, behavior, and viscera

Abstract

Individual differences in response to stress may determine vulnerability to adverse psychological consequences. During a 30 minute social defeat paradigm, Sprague Dawley intruders exhibited individual differences in average latency to be defeated (exhibiting a supine posture) by an aggressive resident Long Evans during 7 daily defeats. Rats responding submissively exhibited short latencies (SL; 197±15 sec) whereas those displaying defensive behaviors exhibited greater latencies (LL; 438±12 sec). All defeated rats exhibited blunted weight gain and adrenal hypertrophy, however when challenged with restraint, LL rats exhibited facilitated adrenocorticotropin hormone response whereas SL exhibited blunted release vs control. SL rats also displayed increased immobility during Porsolt forced swim vs control. As previously reported in mice, SL rats also developed bladder hypertrophy. Corticotropin‐releasing factor (CRF), in addition to its initiating role in the HPA axis and anxiogenic effects, inhibits micturition via barrington's nucleus, thereby inhibiting urination and, in extreme cases, promotes bladder hypertrophy. Immunohistochemical analysis revealed increased CRF‐expressing cells in barrington's of SL. The results implicate a role of individual differences in coping strategy in determining neuroendocrine, neuropeptide, behavioral and visceral repercussions of repeated defeat.