Neonatal capsaicin treatment prevents insulin-stress-induced adrenal catecholamine secretion in vivo: possible involvement of sensory nerves containing substance P.

We have investigated the effects of neonatal capsaicin treatment on stress-induced catecholamine release from adult rats in vivo. Catecholamines released into the inferior vena cava following insulin injection were separated by HPLC and measured by electrochemical detection. Neonatal capsaicin treatment depleted the substance P levels in the splanchnic nerve of adult rats by 70% and prevented the insulin-induced hypoglycaemia from evoking release of adrenaline. The results of this study provide the first evidence in vivo for the neuromodulatory role of sensory nerves containing substance P in the secretion of catecholamines from the adrenal medulla.