Vasoactive intestinal peptide (VIP) is a 28 amino acid neuropeptide that is vasoactive in the intestine. It belongs to a glucagon/secretin superfamily, the ligand of class II G proteincoupled receptors, and it is produced in many tissues of vertebrates including the gut, pancreas, and suprachiasmatic nuclei of the hypothalamus in the brain. VIP functions as a neuromodulator and neurotransmitter, and it is known to regulate muscle activity, epithelial cell secretion, and blood flow in the gastrointestinal tract. This ELISA was developed with serum from rabbits immunized with Vasoactive Intestinal Peptide VIP coupled to a carrier protein.