Effect of pituitary adenylate cyclase activating polypeptide 1-27 on ocular, cerebral and skin blood flow in humans

The aim of the study was to assess the effects of a neuropeptide, pituitary adenylate cyclase activating polypeptide 1-27 (PACAP), on ocular, cerebral and skin blood flow in man. PACAP (0.01-10 pmol kg^-1 min^-1) was administered intravenously to eight healthy male subjects in a placebo- controlled, double-blind dose escalation trial. Fundus pulsation amplitude was measured by laser interferometry, mean blood flow velocity in the ophthalmic artery and the middle cerebral artery measured by Doppler sonography, and regional blood flow of the skin was estimated by laser Doppler flowmetry. Infusion of PACAP at the highest dose of 10 pmol kg^-1 min^-1 induced a significant increase in fundus pulsation amplitude (+83.4%), mean flow velocity in the ophthalmic artery (+91.9%) and regional skin blood flow (+260.3%, P<0.01, ANOVA; each parameter). In contrast, PACAP did not cause any change in middle cerebral artery blood flow velocity or systemic hemodynamics. Our findings indicate that the vasculatures of the eye and the skin are particularly sensitive to PACAP and may implicate a potential role for this peptide in the regulation of blood flow in these vascular beds.