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

Abstract

Effects of electrical stimulation of the gastric vagal nerves on plasma levels of oxytocin (OXT) and arginine vasopressin (AVP) were examined in rats anesthetized with urethane. Electrical stimulation of the gastric vagal nerves 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. Electrical stimulation of the gastric vagal nerves evoked an increase followed by a slight decrease in the concentrations of NA. The responses of spontaneous firing magnocellular neurosecretory neurons in the PVN to both electrical stimulation of the gastric vagal nerves and intravenous (i.v.) administration of CCK-8 were examined. Most of the putative OXT-secreting cells recorded were excited by both electrical stimulation of gastric vagal nerves and i.v. administration of CCK-8. These results suggest that gastric vagal afferents activate the central noradrenergic system from the brainstem to the PVN and secretion of OXT.