REGIONAL CEREBRAL METABOLITES, BLOOD-FLOW, PLASMA-VOLUME, AND MEAN TRANSIT-TIME IN TOTAL CEREBRAL-ISCHEMIA IN THE RAT

Cerebral high-energy metabolites and metabolic end products were measured during and following total cerebral ischemia in the rat. During cerebral ischemia, lactate accumulation was greatest in the hippocampus, followed by the cerebral cortex and striatum. Following reperfusion, the rate of lactate clearance was slower in the hippocampus than in the other two regions. Regional CBF, cerebral plasma volume (CPV), and calculated mean transit time (MTT) were determined following reflow of ischemic tissue. During hyperemia, CPV, used as an indicator of capillary volume, increased concomitantly with CBF while the MTT remained near the control value, suggesting that the linear flow rate through the vasculature was unchanged. During hypoperfusion, CPV returned to control values, but there was a significant increase in MTT that would result from a decreased linear velocity. The finding of normal tissue energy charge, pH(i), and concentration of other metabolites during hypoperfusion shows that hypoperfusion does not result in CBF-metabolic mismatch.