Intracerebroventricular Administration of Growth Hormone Releasing Peptide-6 (GHRP-6) Inhibits Food Intake, but not Food Retention of Crop and Stomach in Neonatal Chicks

Abstract

Growth hormone secretagogues (GHS), including ghrelin, are known to stimulate feeding behavior in mammals. In contrast, intracerebroventricular (ICV) injection of rat or chicken ghrelin, strongly inhibits food intake in chicks. The difference prompted us to compare the effect of growth hormone releasing peptide-6 (GHRP-6), one of synthetic GHSs on feeding behavior of chicks with that of ghrelin. Gastric motility stimulating action of GHRP-6 was also examined in vivo measuring retention of food in digestive tracts. ICV injection of GHRP-6 (0.38nmol-1.5nmol) dose-dependently inhibited food intake of neonatal chicks under both ad libitum and fasting conditions. The anorexic effect of GHRP-6 was attenuated by D-Lys3-GHRP-6 (GHS receptor antagonist) in a dose dependent manner. Central injection of GHS agonist and/or antagonist did not affect food retention in crop, proventriculus and gizzard. These results suggest that central injection of synthetic GHS, GHRP-6 inhibits feeding behavior as dose ghrelin without affecting gastrointestinal motility in layer chicks.