Cytochrome oxidase activity during acute focal ischaemia in rat brain. A pathophysiology of acute focal ischaemia: Part 2.

An enzyme-histochemical technique was used to examine the changes in cytochrome oxidase activity during acute focal ischaemia in the rat. In the somatosensory cortex, the enzyme activity began to increase significantly (p < 0.01) 1 hour after middle cerebral artery occlusion (MCAO) and continued to increase up to 3 hours, during which ischaemic cell damage was not detected. In the striatum, the enzyme activity increased significantly (p < 0.01) 1 hour after MCAO in the absence of morphological evidence of ischaemic cell damage; a peak activity was reached at 2 hours, and began to decline 3 hours after MCAO when moderate ischaemic change was detected. In both cortical and subcortical areas, the enzyme activity tended to decrease from 4 hours after MCAO, and was reduced to a level similar to or below that of the non-ischaemic hemisphere 5 hours after MCAO, when severe ischaemic damage was demonstrated. The relation of this transient increase of cytochrome oxidase activity in the early stage of acute ischaemia and the hypermetabolism of neuronal cells during ischaemic insult was discussed.