Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) receptors are activated by the endogenous peptides VIP, PACAP-38, PACAP-27, peptide histidine isoleucineamide (PHI), peptide histidine methionineamide (PHM) and peptide histidine valine (PHV). “PACAP type II receptors” (VPAC1 and VPAC2 receptors) display comparable affinity for PACAP and VIP, whereas PACAP-27 and PACAP-38 are >100 fold more potent than VIP as agonists of most isoforms of the PAC1 receptor.[3]
^Laburthe M, Couvineau A, Marie JC (2002). "VPAC receptors for VIP and PACAP". Recept. Channels. 8 (3–4): 137–53. doi:10.3109/10606820213680. PMID12529932.
^"VIP and PACAP receptors". IUPHAR Guide to Pharmacology. The British Pharmacological Society (BPS) and the International Union of Basic and Clinical Pharmacology (IUPHAR).