Distribution and dilatory effect of vasoactive intestinal polypeptide (VIP) in human cerebral arteries.

Vasoactive intestinal polypeptide (VIP)-containing nerve fibers were demonstrated in human pial arteries by immunocytochemistry. Fine varicose fibers were located in the adventitia close to the media layer. Measurements by radioimmunoassay revealed concentrations of VIP between 0.7 and 2.7 pmol/g in the major arteries at the base of the brain, obtained at autopsy. Isolated human pial arteries, obtained in conjunction with neurosurgery, relaxed in a concentration-dependent manner upon administration of VIP. The relaxation of the vessels amounted to 57 +/- 9% of the contraction elicited by prostaglandin F2 alpha (2.5 microM) with an EC50 value of (8.5 +/- 1.2) X 10(-9) M.