抄録
Ghrelin is a recently identified endogenous legand for the grows hormone secretagogue receptor (GHS-R). In addition to GH-releasing activity, ghrelin enhances feeding. Since swallowing is early step of feeding behavior, ghrelin might modify swallowing. In the present study, we examined the effects of ghrelin on the reflex swallowing using anaesthetized rats. Ghrelin, which was dissolved in Ringer,s solution, was administered into the fourth ventricle. Swallowing was induced by the electrical stimulation (20 Hz, 0.2 mA, 20 sec) of the central cut end of the superior laryngeal nerve (SLN) and was monitored by recording the electromyogram of the mylohyoideus muscle. The number of swallowing during the electrical stimulation of the SLN decreased after the administration of ghrelin in a dose-dependent manner. The latency of the response tended to be longer in the presence of ghrelin. Simultaneous administration of ghrelin and GHS-R antagonist ([D-Lys3] GHRP-6) did not change the number of swallowing induced by the electrical stimulation of the SLN. After sectioning both vagi at the cervical level below where the SLN entered the vagal trunk, the inhibitory response of swallowing induced by ghrelin was still observed. Neither mean blood pressure nor mean heart rate changed after the administration of ghrelin. These results suggest that ghrelin inhibits reflex swallowing modifying the neural activities of the dorsal medulla where swallowing center is present. [J Physiol Sci. 2007;57 Suppl:S236]
