Hypoxic and hypoglycaemic changes of intracellular pH in cerebral cortical pyramidal neurones

Intracellular pH and membrane potential were measured during hypoxia and/or hypoglycaemia in cortical pyramidal neurones of a rat cortical slice preparation. Intracellular pH (pH(i)) was calculated from ratiometric microfluorometry of the pH-sensitive dye BCECF injected via sharp recording microelectrodes into the neurones. Transient (5 min) hypoxia induced a fall of pH(i) (7.12 ± 0.03) of -0.72 ± 0.11 pH units while transient (10 min) hypoglycaemia induced an increase of 0.37 ± 0.09 pH units. Hypoglycaemia did not prevent the hypoxic acidification. Lowering extracellular Na⁺ induced a membrane hyperpolarization and alkalinization by 0.29 ± 0.12 pH units but did not affect the development or recovery of the hypoxic acidification. The alkalinization during hypoglycaemia suggested that there is some anaerobic glycolysis under normoglycemic conditions. The hypoxic acidification, however, is unlikely to result from anaerobic glycolysis or reversal of Na⁺- dependent H⁺ extrusion.