Psychosocial stress affects the involvement of prostaglandins and nitric oxide in the lipopolysaccharide-induced hypothalamic-pituitary-adrenal response

The role of prostaglandins and nitric oxide (NO), generated after peripheral lipopolysaccharide (LPS) administration, in the adaptation of hypothalamic-pituitary-adrenal (HPA) axis under stressful circumstances remains to be elucidated. The aim of the present study was to assess the effect of chronic repetitive restraint or social crowding stress on the involvement of nitric oxide and prostaglandins in the LPS-induced pituitary-adrenocortical response. Male Wistar rats were restrained in metal tubes 2x10 min/day or crowded in cages for 7 days prior to treatment. All compounds were injected i.p., cyclooxygenase (COX) and nitric oxide synthase (NOS) inhibitors 15 min before LPS. Two hrs after injection LPS induced a significant increase in ACTH and corticosterone secretion. Repeated restraint impaired more potently than crowding stress the LPS-induced HPA-response. Indomethacin, a non-selective COX inhibitor, considerably reduced the LPS-induced HPA response in non-stressed rats and to a lesser extent diminished this response in repeatedly restrained or crowded rats. Neuronal NOS inhibitor, N omega-nitro-L-arginine decreased the LPS-induced HPA response, more potently in control than crowded rats. Aminoguanidine, an NOS inhibitor, diminished the LPS-elicited ACTH response in crowded rats. These results indicate that prostaglandins and NO generated by neuronal and inducible NOS are involved in the LPS-induced HPA axis response under basal conditions and during its adaptation to chronic social stress circumstances.