Feeding response following central administration of chicken vasoactive intestinal peptide in chicks

Vasoactive intestinal peptide (VIP) is expressed in central nervous systems and peripheral tissues across lower and higher vertebrates and is involved in many physiological functions. One of these functions is appetite regulation; however the mechanisms mediating this response are poorly understood. Therefore, the purpose of this study was to investigate central mechanisms of VIP induction of satiety using chicks as models. Intracerebroventricular (ICV) injection of VIP (0.1 and 0.5 nmol) significantly decreased food intake under both ad libitum and food deprivation conditions and chicken VIP (cVIP) was more potent than mammalian VIP. The mechanisms involved with the VIP-induced anorexigenic effect were investigated by studying the involvement of the central corticotrophin-releasing hormone (CRH) systems. ICV injection of cVIP caused increased plasma corticosterone concentration and decreased diencephalic mRNA expression of CRH, CRH receptor-2 (CRH-R2) and urocortin 3 (UCN-3, which has high affinity for CRH-R2). This simultaneous decrease in the expression of ligands and their receptor, with the increase in plasma corticosterone concentration suggests that the anorexigenic effect of cVIP might be related to CRH systems. The cVIP-induced anorexigenic effect was partly attenuated by co-injection of astressin, a CRH-R2 antagonist, supporting this thesis. The present study demonstrated that VIP inhibits feeding behavior via CRH systems in the brain of chicks.