Cerebral circulation. Effects of vasodilating drugs on blood flow and the microvasculature of ischemic and nonischemic cerebral cortex.

Abstract

Vasoactive drugs were given intravenously to 14 cats that had unilateral occlusion of a middle cerebral artery. Measurements of cortical blood flow (CBF) and observations of the superficial cortical microvasculature were made bilaterally before and after the injection of each drug. Papaverine produced increases of CBF of the nonischemic hemispheres of seven of eight animals despite decreases of mean systemic arterial blood pressure (MABP). Hexobendine also produced decreases of MABP, but CBF increased in only two of six animals. Blood flow did not increase in any of the three animals given ergot alkaloids (Hydergine). None of the drugs consistently produced increases of CBF of the ischemic hemispheres. Decreases of CBF that occurred in the ischemic hemispheres were related to decreases of MABP and impairment of autoregulatory processes. Paradoxic responses to increases of arterial carbon dioxide tension occurred in three animals.