Activation of gastric afferents increases noradrenaline release in the paraventricular nucleus and plasma oxytocin level

Effects of electrical stimulation of the gastric vagal nerves on plasma lev els of oxytocin (OXT) and arginine vasopressin (AVP) were examined in rats anesthetized with urethane. Electrical stimulation of the gastric vagal ner ves increased the plasma levels of OXT, but not AVP. The concentrations of extracellular noradrenaline (NA) in the paraventricular nucleus (PVN) were measured by in vivo microdialysis in rats anesthetized with urethane. Elect rical stimulation of the gastric vagal nerves evoked an increase followed b y a slight decrease in the concentrations of NA. The responses of spontaneo us firing magnocellular neurosecretory neurons in the PVN to both electrica l stimulation of the gastric vagal nerves and intravenous (i.v.) administra tion of CCK-8 were examined. Most of the putative OXT-secreting cells recor ded were excited by both electrical stimulation of gastric vagal nerves and i.v. administration of CCK-8. These results suggest that gastric vagal aff erents activate the central noradrenergic system from the brainstem to the PVN and secretion of OXT. (C) 2000 Elsevier Science B.V. All rights reserve d.