Morphological evidence of cellular death caused by an ischemic insult is commonly detected by TTC stain. TTC is a sensitive histochemical indicator of mitochondrial respiratory enzyme funtion. Therefore, brain lesion identified by TTC stain indicates that tissues were irreversibly impaired in mitochondrial function and oxidative respiratory enzyme systems. Our result revealed that naloxone can restore mitochondrial activity following cerebral I/R stress,and thus reduced infarct volume. In concert with this result,naloxone obviously favored restoration of energy metabolism as indicated by reduction in cerebral I/R-induced extracellular accumulation if lactate, decrease of pyruvate and increase of L/P ratio