Dynamic changes in glucose and lactate in the cortex of the freely moving rat monitored using microdialysis

These experiments for the first time examine simultaneous changes in glucose and lactate in unanaesthetised animals during moderate hypoxia. Unanaesthetised rats were exposed to moderate hypoxia for a period of 15 min by reducing inspired oxygen to 8%. Changes in glucose and lactate were monitored in rat cortex using microdialysis and a novel dual enzyme-based assay. Samples of dialysate collected at 3-min intervals were assayed for both glucose and lactate. There was an early rapid rise of lactate that reached a peak at the end of the period of hypoxia followed by a steep decline. Glucose showed a very much smaller delayed increase that started during the period of hypoxia and continued beyond it. The origin of the rise in glucose is discussed, using the temporal relationship between the lactate and glucose changes.