Effect of different forms of vasoactive intestinal peptide on cAMP formation in the mammalian cerebral cortex

Chicken, guinea pig and mammalian (human/porcine/rat) vasoactive intestinal peptides (VIP; 0.001-3 microM) were compared with respect to their ability to stimulate adenosine 3', 5'-cyclic monophosphate (cAMP) formation in the cerebral cortical slices of rat and guinea pig. Of the tested peptides, i.e. chicken VIP (cVIP), guinea pig VIP (gpVIP) and human/rat/porcine (mammalian) VIP (mVIP), the strongest stimulator of cAMP synthesis was cVIP, and the weakest one - the gpVIP. Pituitary adenylate cyclase-activating polypeptide (PACAP) used as a reference drug at 0.1 microM concentration strongly stimulated cAMP formation in the cerebrum of both species, being, however, significantly more potent in the guinea pig model. The obtained data demonstrate significant differences in biological activity between cVIP and two distinct mammalian VIPs in the cerebral cortex of rat and guinea pig.