Gastric afferents to the paraventricular nucleus in the rat.

Extracellular recordings were made from vasopressin (AVP) and oxytocin (OXT)-secreting cells in the paraventricular nucleus (PVN) of the hypothalamus in rats anesthetized with urethane-chloralose to determine the effects of electrical stimulation of vagal gastric nerves and gastric distension on their activity. Electrical stimulation of gastric branches of the vagus nerves inhibited 5 and excited 10 of 32 phasically firing neurosecretory cells. Approximately one third of the phasically firing neurosecretory cells (9 out of 29 cells) were transiently inhibited by gastric distension; an effect which was completely abolished by bilateral cervical vagotomy. In contrast, gastric nerve stimulation excited 45 of 72 non-phasically firing paraventricular cells. Thirteen of 77 non-phasically firing cells tested were excited by gastric distension. We conclude that there are some sensory afferent inputs originating from gastric receptors and transmitted by gastric vagal afferents which inhibit the activity of AVP-secreting neurons in the PVN although other inputs excite the cells. Similar inputs also excite some of the putative OXT-secreting neurons in the PVN.