AJP - Heart and Circulatory Physiology, Vol 239, Issue 6 765-H768, Copyright © 1980 by American Physiological Society
Mechanism of action of vasoactive intestinal polypeptide on cerebral arterioles
E. P. Wei, H. A. Kontos and S. I. Said
The effect of vasoactive intestinal polypeptide (VIP) on cerebral
arterioles was examined in anesthetized cats equipped with an acutely
implanted cranial window for the observation of the pial microcirculation.
Topical application of VIP on the surface of the brain in doses of 0.01-1.0
microgram/ml produced a dose-related vasodilation that was of equal
magnitude in small (< 100 micrometer diam) and large (> 100
micrometer diam) pial arterioles. The maximum dilation averaged 20% of the
control diameter. There were no associated changes in arterial blood
pressure or in arterial CO2 tension. In additional experiments the
vasodilator effect of VIP was completely inhibited by pretreatment with
intravenous indomethacin or AHR-5850. These nonsteroidal anti-inflammatory
drugs inhibit cyclooxygenase activity and thereby interfere with the
synthesis of prostaglandins and related compounds. The vasodilator effect
to topical histamine was unaffected by indomethacin and AHR-5850. The
results show that VIP has a strong vasodilator effect on pial arterioles of
the cat and suggest that this effect is mediated by prostaglandins.
