Oro-pharyngeal chemoreceptor activation induces gastric motor response in healthy volunteer subjects

Previous study has revealed that water-responsive afferent neurons in the superior laryngeal nerve induced inhibition of motility in the proximal and distal stomach using anaesthetized rats. These gastric responses might facilitate the reservoir function of the stomach. To confirm the gastric responses discovered in rats also occur in humans, we evaluated gastric myoelectrical activities in healthy volunteer subjects during fluid intake using electrogastrography. Before human experiments, we recorded the myoelectrical activities in rats to evaluate the response induced by the administration of water into the larynx. A large deflection in the gastric myoelectrical activities was observed just after the administration of water in anesthetized rats. A similar large deflection was also observed just after voluntary swallowing of 20 ml water in humans. The swallowing of saliva did not induce such response. We further observed the gastric response during reflex swallowing elicited by slow infusion of isotonic saline, water or 0.05 M citric acid on to the posterior tongue. Infusion of water and citric acid but not 0.15 M saline induced significant changes in mean relative ratio of the response. These electrogastrographic responses induced by the infusion of liquids strongly suggest that the gastric motor response facilitates reservoir function of the stomach during liquid intake in humans as well as in rats.