Intracerebroventricular injection of vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibits feeding in chicks

Previous research has indicated an involvement of glucagon superfamily peptides in the regulation of feeding in the domestic chick brain. However the possible roles of vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide-38 (PACAP) have not yet been investigated. We therefore examined the effect of intracerebroventricular (ICV) injections of VIP or PACAP on food intake in chicks. ICV injection of both VIP and PACAP significantly inhibited food intake over 4 h at doses ranging from 12 to 188 pmol. Subsequently, we compared the anorexic effect the glucagon superfamily peptides VIP, PACAP, growth hormone-releasing factor (GRF) and glucagon-like peptide-1 (GLP-1) after ICV injection at an equimolar dose (12 pmol). All four peptides significantly inhibited food intake, although the anorexic effects of VIP and PACAP were weaker than those of GRF and GLP-1. These findings support the hypothesis that glucagon superfamily peptides play an important role in the regulation of appetite in the chick brain.