PACAP (1-38), human, ovine, rat is a 38-amino acid neuropeptide with the physiological function of binding to PACAP type I receptors. PACAP (1-38) has a high affinity for PACAP-specific (PAC1) receptors in the membranes of various tissues including the endocrine pancreas, and PACAP (1-38) can relax the smooth muscle of the trachea.