There are two known receptors for the vasoactive intestinal peptide (VIP) termed VPAC1 and VPAC2.
[1][2] These receptors bind both VIP and pituitary adenylate cyclase-activating polypeptide (PACAP) to some degree.
VPAC1 is distributed widely in the CNS, liver, lung, intestine and T-lymphocytes.
VPAC2 is found in the CNS, pancreas, skeletal muscle, heart, kidney, adipose tissue, testis, and stomach.
“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.