Abstract
Chronological changes in regional cerebral blood flow (rCBF) and in the regional cerebral metabolic rate for glucose (rCMRGIu) were studied by a double tracer autoradiographic method in regions of local ischemia in rabbit brains. Local ischemia was produced by cautery of the bilateral vertebral artery, followed several days later by cautery of the left middle cerebral artery through a transorbital approach and ligation of the left common carotid artery. Autoradiography was performed, 2 hours, 6 hours, and 4 days after occlusion, by a double tracer method involving the use of 14Ciodo-antipyrine and 18F-fluoro-deoxyglucose. Absolute rCBF values were estimated by Sakurada's method and rCMRGIu values by Hutchins' formula. Histological examination was performed concurrently with the rCBF and rCMRGIu study. Mildly ischemic lesions (rCBF of 25 to 40 ml/100 g/ min) were detected in the superior portion of the left frontal lobe, the left parietal lobe, and the left occipital lobe. Severely ischemic lesions (rCBF below 25 ml/100 g/min) were found in the lateral part of the left frontal lobe, the left temporal lobe, and the left caudate nucleus. In the mildly ischemic regions, rCMRGIu decreased in proportion to the decrease in rCBF. That is, matched low perfusion was observed, but there were no histological abnormalities. In severe ischemia the situation was quite different. Two hours after occlusion, most areas showed a decrease in rCMRGIu in proportion to the decrease in rCBF. However, 6 hours after occlusion, rCMRGIu decreased nonuniformly: in some places the decrease was dramatic and in others, rCMRGIu residue was found. Four days after occlusion, the reduction in rCMRGIu was again proportional to the rCBF decrease. In severely ischemic regions, necrosis was observed 4 days after occlusion. Thus, disturbance of glucose metabolism and eventual tissue necrosis occurred in severely ischemic regions. Moreover, the results suggest that nonuniformity of the decrease in rCMRGIu may have prognostic significance in cases of severe ischemic brain insult.
