VIP peptides cause vasodilation, lowers arterial blood pressure, stimulates myocardial contractility, increases glycogenolysis and relaxes the smooth muscle of trachea, stomach, and gall bladder. The vasoactive intestinal peptide (VIP) is a 28-aa long peptide corresponding to aa45-72 of the guinea pig VIP precursor after cleavage. VIP is a neuropeptide synthesized in the central nervous system, which enhances the formation of adenosine 3'-5'-cyclic monophosphate in cerebral cortex and hypothalamus. VIP also modulates the cholinergic as well as serotonergic neurotransmitter systems.Guinea Pig: H-His-Ser-Asp-Ala-Leu-Phe-Thr-Asp-Thr-Tyr-Thr-Arg-Leu-Arg-Lys-Gln-Met-Ala-Met-Lys-Lys-Tyr-Leu-Asn-Ser-Val-Leu-Asn-NH2 or H-HSDALFTDTYTRLRKQMAMKKYLNSVLN-NH2