R Farrokhi - Department of Basic Sciences, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran
V Babapour - Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
M Zendehdel - Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
A Asghari - Department of Clinical Science, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran
H Gilanpour - Department of Basic Sciences, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran

The present study aimed to identify the role of dopaminergic and cannabinoidergic systems in the ghrelin-induced hypophagia among meat-type chickens. In the first experiment, intracerebroventricular (ICV) injection was applied to birds with control solution, D۱ receptor antagonist (۵ nmol), ghrelin (۶ nmol), and D۱ receptor antagonist plus ghrelin. The second to sixth experiments were similar to the first one, with the difference that D۲ receptor antagonist (۵ nmol), D۳ receptor antagonist (۶.۴ nmol), D۴ receptor antagonist (۶ nmol), the precursor of dopamine (۱۲۵ nmol), and ۶-hydroxy dopamine (۱۵۰ nmol) instead of D۱ antagonist were injected into the broiler chickens. In experiment ۷, control solution and different levels of ghrelin antagonists (۵, ۱۰, and ۲۰ nmol) were injected. In experiment ۸, the chickens were ICV injected with control solution, ghrelin antagonist (۱۰ nmol), dopamine (۴۰ nmol), and ghrelin antagonist plus dopamine. In experiments ۹ and ۱۰, CB۱ and CB۲ receptors antagonist (۶.۲۵µg and ۵µg) were co-injected with ghrelin (۶ nmol), respectively, measuring the food intake for ۱۲۰ min after the injection. It was observed that ghrelin ICV injection considerably reduced food intake, whereas ghrelin antagonist increased food intake, depending on the dose (P<۰.۰۵). In addition, ghrelin-induced hypophagia was significantly attenuated by D۱ receptor antagonist and ۶-hydroxy dopamine (P<۰.۰۵), while the dopamine precursor considerably elevated the ghrelin-induced food intake (P<۰.۰۵). The dopamine-induced feeding behavior was diminished by the co-administration of [D-Lys-۳]-GHRP-۶ (۱۰ nmol)+dopamine (۴۰ nmol) (P<۰.۰۵). In addition, CB۱ receptor antagonists enhanced the ghrelin influence on food intake (P<۰.۰۵). The results implied that the hypophagic impact of ghrelin was probably mediated by D۱ and CB۱ receptors within neonatal broilers.

Ghrelin, Cannabinoid, Dopamine, Broiler chicken, Food intake