抄録
Our previous studies revealed that orexin-A and neuropeptide Y, which are potent orexigenic peptides, induced relaxation of the proximal stomach. This relaxation probably facilitates reservoir function of the stomach. Ghrelin is a recently identified endogenous legand for the grows hormone secretagogue receptor (GHS-R) and has orexigenic effect. Up to the present, the effect of ghrelin on the proximal stomach motility is not known. In the present study, the effect of ghrelin on motility of the proximal stomach was examined in anaesthetized rats. Intragastric pressure (IGP) was measured using a balloon situated in the proximal part of the stomach. The administration of ghrelin into the fourth ventricle induced relaxation of the proximal stomach in a dose-dependent manner. Simultaneous administration of ghrelin and GHS-R antagonist ([D-Lys3] GHRP-6) did not induce significant change in IGP. Microinjections of ghrelin into the dorsal vagal complex (DVC) also induced relaxation of the proximal stomach. Immunohistochemical staining for GHS-R showed labeled cells in the DVC, where most of cells were appeared in the nucleus of the solitary tract and the dorsal motor nucleus of the vagus. The bilateral sectioning of the vagi at the cervical level abolished the relaxation induced by the administration of ghrelin into the fourth ventricle. These results indicate that ghrelin induces the relaxation of the proximal stomach via the GHS-R situated in the DVC. [J Physiol Sci. 2007;57 Suppl:S218]
