Cerebral cortical blood flow during changes of acid-base equilibrium of the brain.

Abstract

In anesthetized cats, cortical blood flow, cortical pH, cortical PCO2 [CO2 pressure], cortical PO2 [O2 pressure] on the suprasylvian gyrus, arterial blood pressure, arterial pH, and end-expiratory CO2 content were recorded simultaneously. In respiratory acidosis (caused by CO2 inhalation), metabolic acidosis of the blood (intravenous injection of HC1), metabolic alkalosis of the blood (intravenous injection of NaHCO3), respiratory alkalosis (hyperventila-tion), and in posthypoxic reactive hyperemia (inhalation of nitrogen, 2-4 mia) the reactions were followed for 15 min. During this time the cortical extracellular pH was correlated with the cortical vascular resistance, whereas PCO2, PO2, end-expiratory CO2 content, arterial pH, and arterial blood pressure were not always correlated with cortical vascular resistance. The significance of the extracellular cortical pH is discussed. Interactions of other mechanisms for the regulation of cortical vascular resistance were demonstrated by experiments with injections of Papaverin and artificially produced cerebral edema. The cortical extracellular pH has a key position for the regulation of cortical vascular resistance and for the blood flow of the vessels on the cortical surface.