Evaluating the Role of Corticotropin Receptors on Feed Intake Using Melanocortin Receptor Agonists in Neonatal Broilers

Evidence from animal studies suggests corticotrophin and melanocortin systems have regulatory role in feeding system in avian, but there is no evidence for their interaction. In this survey three experiments designed to investigate the role of corticotrophin receptors on food intake using melanocortin receptors agonist M3 and M4 in neonatal chicken (each experiment includes 4 groups and 11 birds in each group). In experiment 1, chickens were intracerebroventricularly (ICV) injected with control solution, MTII (MC3/MC4 receptors agonist; 2.45, 4.8 and 9.8 pmol). In experiment 2, control solution, MTII (9.8 pmol), astressin-B (CRF1/ CRF2 receptors antagonist; 30 µg), and MTII + astressin-B were injected. In experiment 3, control solution, MTII (9.8 pmol), astressin-2B (CRF2 receptors antagonist; 30 µg), and MTII + astressin-2B were injected. Then, cumulative feed intake was recorded until 120 min after injection. According to the results, dose dependent hypophagia observed after ICV injection of the MTII (p<0.05). ICV injection of MTII (9.8 pmol) + astressin-B had no effect on the hypophagic effect of the MTII (p> 0.05). ICV injection of MTII (9.8 pmol) + astressin-2B significnatly diminished MTII-induced hypophagia (p<0.05). These results suggest that inducing hypophagia by melanocortin mediates via corticotropin CRF2 receptors in broiler chicken.