Cerebral circulatory and metabolic effects of vasoactive intestinal polypeptide.

Two aspects of the action of vasoactive intestinal polypeptide (VIP) within the cerebral vascular bed have been examined. First, in anesthetized rats, the vasomotor responses of individual pial arterioles on the convexity of cerebral cortex to the perivascular microinjection of vasoactive intestinal polypeptide were examined and, second, in anesthetized baboons, the effects of VIP on cerebral blood flow, cerebral oxygen consumption, and the electroencephalogram (EEG) were investigated both prior to and following the osmotic opening of the blood-brain barrier. The perivascular microinjection of VIP resulted in statistically significant increase in arteriolar caliber in the concentration range 10(-9) to 10(-6) M. For example, arteriolar caliber was increased by 22 +/- 3% (mean +/- SE) following the injection of VIP (10(-8) M). In the second series, in baboons, the intracarotid infusion of vasoactive intestinal polypeptide (10(-11) mol/min) did not affect cerebral blood flow, cerebral oxygen consumption, or the EEG under normal circumstances. If the same concentration of vasoactive intestinal polypeptide was administered following hypertonic opening of the blood-brain barrier, cerebral blood flow and oxygen consumption were both elevated (by 37 +/- 7% and 28 +/- 10%, respectively), accompanied by increased EEG activity.