The effects of pituitary adenylate cyclase-activating polypeptide on cerebral arteries and vertebral artery blood flow in anesthetized dogs

We investigated and compared the effects of pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) on cerebral circulation in anesthetized dogs. The intracisternal administration of PACAP-27, PACAP-38, and VIP dilated canine cerebral arteries in a dose-dependent manner. A 10 nmol dose of PACAP-27, PACAP-38, and VIP dilated the basilar artery by 23 ± 3, 27 ± 3 and 30 ± 3%, respectively. Rostrally located arteries tended to be more responsive to PACAP-27. Pretreatment with N G-monomethyl- l-arginine did not affect PACAP-27-induced vasodilation. Vertebral artery blood flow was also affected by intra-arterial injection of these peptides in a dose-dependent manner. A 100 pmol dose of PACAP-27, PACAP-38, and VIP increased the vertebral artery blood flow by 42 ± 10, 29 ± 4, and 62 ± 11%, respectively. The VIP receptor antagonist, [Lys 1,Pro 2,5,Arg 3,4,Tyr 6]VIP, inhibited both the VIP- and PACAP-38-induced increase in vertebral artery blood flow. These findings suggest that PACAP plays a role in the regulation of cerebral circulation.