Ventral medullary extracellular fluid pH and blood flow during hypoxia

Publisher Website
Google Scholar
Abstract
Vascular responses of the ventral medulla and total brain to 30-60 min of isocapnic hypoxia (PaO2 [arterial O2 partial pressure] = 32 .+-. 2 Torr) were examined using radioactive microspheres in anesthetized, paralyzed and artificially ventilated cats. Ventral medullary extracellular fluid (ECF) pH was measured using pH microelectrodes with tip diameters of 1-2 .mu.m. Total brain blood flow (.ovrhdot.Q) increased significantly from a control value of 53 .+-. 8 (mean .+-. SE) to 160 .+-. 42 ml .cntdot. 100 g-1 .cntdot. min-1 following 30-60 min of hypoxia. Ventral medullary .ovrhdot.Q increased from 28 .+-. 5 to 97 .+-. 20 ml .cntdot. 100 g-1 .cntdot. min-1 and ECF pH decreased by 0.15 .+-. 0.06 pH U. .ovrhdot.Q responses are attributable to decreased vascular resistance as arterial pressure remained constant. The sensitivity of the ventral medullary vasculature to isocapnic hypoxia did not differ from that of the brain as a whole. Under the conditions of the experiment, the ventral medullary vascular response to hypoxia is not sufficient to stabilize local ECF pH. The observation of simultaneously reduced pH and increased .ovrhdot.Q is consistent with a role for ECF H+ in mediating the cerebrovascular response to hypoxia.

This publication has 0 references indexed in Scilit: