Possible roles of central cholinergic nicotinic mechanisms in regulation of gastric functions

The effect of nicotine microinjected into various hypothalamic regions and ala cinerea on gastric acid output and mucosal blood flow was examined in rats anesthetized with urethane. After administration of nicotine, 3 nmol, a marked increase in gastric acid output was observed in rats in which the tip of the micropipette was applied to the caudal portion of the ventromedial hypothalamus (VMH) and ala cinerea. Microinjection of physiological saline into ala cinerea also enhanced gastric acid output. Nicotine was without effect when microinjected into other hypothalamic regions. The increase in gastric acid output induced by microinjection of nicotine into the caudal portion of VMH was completely blocked by the concomitant administration of hexamethonium, 50 nmol, but was not modified in reserpine-pretreated animals. Intraventricularly applied nicotine increased the gastric acid output; this increase was abolished following bilateral destruction of VMH. The increase in gastric acid output was always in parallel with the increase in mucosal blood flow. These results suggest that cholinergic nicotinic receptors in the VMH are concerned with central regulation of gastric functions.