Abstract
Potent appetite-stimulating effects of neuropeptide Y (NPY) are well known. The present study undertook to demonstrate that the role of NPY in gastric relaxation 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 NPY into the fourth ventricle induced relaxation of the proximal stomach in a dose-dependent manner. The administration of an Y1 receptor agonist [Leu31, Pro34] NPY induced a larger relaxation than NPY. The administration of an Y2 receptor agonist (NPY13-36) did not induce significant changes in motility. Microinjection of [Leu31, Pro34] NPY into the caudal part of the dorsal vagal complex (DVC) induced relaxation of the proximal stomach. In contrast, similar injections into the intermediate part of the DVC increased IGP of the proximal stomach. The administration of NPY into the fourth ventricle did not induce relaxation after bilateral injections of the Y1 receptor antagonist (1229U91) into the caudal DVC. Bilateral vagotomy below the diaphragm abolished the relaxation induced by the administration of NPY into the fourth ventricle. The intravenous injection of atropine methyl nitrate reduced the magnitude of relaxation induced by the administration of NPY. These results indicate that NPY induces relaxation in the proximal stomach via Y1 receptors situated in the DVC. This work was supported by a Grant-in-Aid for Scientific Research from the Japanese Society for the Promotion of Science to MK. [J Physiol Sci. 2006;56 Suppl:S142]
