Social stress inhibits the nitric oxide effect on the corticotropin-releasing hormone- but not vasopressin-induced pituitary-adrenocortical responsiveness

Putative involvement of endogenous nitric oxide (NO) in the corticotropin-r eleasing hormone (CRH, I mu g/kg i.p.)- and vasopressin (AVP, 5 mu g/kg i.p .)-induced ACTH and corticosterone secretion was investigated in both non-s tressed and crowded rats. The NO synthase blocker Nw-nitro-L-arginine ((L)- NNA, 2 mg/kg i.p.) significantly augmented the AVP-induced ACTH and cortico sterone secretion in control and stressed rats, but it increased the CRH-in duced ACTH response only in control rats. Crowding stress did not affect th e L-NNA evoked increase in AVP-induced hormone responses, but it abolished the CRH-induced ACTH response. (C) 1999 Elsevier Science B,V.