Water stimulation of the posterior oral cavity induces inhibition of gastric motility

The response of gastric motility to the administration of water and saline in the larynx and epiglottis was investigated in urethanchloralose anesthet ized rats. Administration of water inhibited motility of the distal stomach , but 0.15 M NaCl did not induce the inhibitory response. Bilateral section ing of the superior laryngeal nerve (SLN) abolished the inhibitory response induced by water. Bilateral cervical vagotomies abolished the inhibitory r esponses, although spinal transection did not affect the inhibitory respons e. These inhibitory responses have been observed in immobilized animals. Th e degree of inhibition by water and hypotonic saline was negatively correla ted with the sodium concentration. In contrast, the degree of inhibition to hypertonic saline was positively correlated with the sodium concentration. The proximal stomach also showed a reduction in intragastric pressure in r esponse to the administration of water. These findings suggest that water-r esponsive afferent neurons in the SLN suppress gastric motility via the vag al efferent nerve.