Vasoactive intestinal peptide-stimulated adenosine 3',5'-cyclic monophosphate formation in cerebral cortex and hypothalamus of chick and rat: comparison of the chicken and mammalian peptide.

Chicken and mammalian (human/porcine/rat) vasoactive intestinal peptides (VIP; 0.01-3 microM), whose structures differ by four amino acid residues in 11, 13, 26 and 28 positions, were compared with respect to their ability to stimulate adenosine 3',5'-cyclic monophosphate (cyclic AMP) formation in the hypothalamus and cerebral cortex of chick and rat. In four tested biological systems, the chicken VIP appeared to be significantly more potent in evoking cyclic AMP response than its mammalian counterpart, the differences were more pronounced in the chick tissues, particularly in the hypothalamus, where the mammalian peptide produced only weak (but significant) effect at the highest used dose, i.e. 3 microM. Pituitary adenylate cyclase-activating polypeptide, a VIP-like peptide, applied as a reference drug at 0.1 microM, strongly stimulated cyclic AMP formation in all tested systems. The data demonstrate significant quantitative differences in biological activity between mammalian and non-mammalian peptides tested in brain tissue of chicks and rats, indicating that usage of the mammalian VIP in at least 'avian' studies may lead to some false conclusions.