Focal Transient Cerebral Ischemia in the Squirrel Monkey

Cerebral adenosine triphosphate and lactate concentrations were measured in the squirrel monkey ( Saimiri sciureus ) before, during, and at selected times after various periods of middle cerebral artery occlusion. The gradual decrease in ATP to 55, 35, and 20%, of normal and the increase in lactate to 7, 8, and 10 times normal after 2, 3, and 4 hours of occlusion, respectively, were reversible with restoration of flow. Electrocorticograms recorded in acute preparations indicated potential for recovery. The correlation of lactate levels with previous determinations of blood flow in this preparation supports the theory that loss of autoregulation and "luxury perfusion" in cerebral ischemia results from localized metabolic acidosis due to accumulation of lactic acid. In a separate group of monkeys, the ischemic lesions were found to be largely reversible after 2 or 3 hours and irreversible after 4 hours of middle cerebral artery occlusion; the cause of death in the monkeys subjected to 4 hours of occlusion was edema, which progressed even after restoration of flow.