一時的脳虚血における脳神経組織のreversibilityに関する研究

Abstract

This study was undertaken to determine the inchemic time threshold for brain damage and the critical time threshold for fatal damage after reperfusion using a middle cerebral artery (MCA) occlusion model in adult cats. The MCA was exposed by the transorbital approach and temporarily obstructed by Zen's clip. Animals were divided into 10 groups of 8 cats each according to ischemic times of 10, 20, 30 minutes and 1, 2, 4, 6, 8, 12 and 24 hours. A cranial window was made above the ectosylvian gyrus, which has poor anastomosis. The reactivity of the pial arteriole was observed through the cranial-window and evaluated using an intravital microscope and videoangiometer, and regional cerebral blood flow (rCBF) was simultaneously continuously measured by lased doppler flowmetry. In each group, rCBF was quantitatively measured by autoradiography 5 hours after reperfusion and histological study was also performed. For ischemic time of less than 20 minutes, vessel reactivity was preserved blood-brain barrier (BBB) intact ; ICP was unchanged and rCBF promptly returned to pre-ischemic levels after reperfusion. Although no infarction was found at 30 minutes of inchemia, vessel rectivity was slightly impaired, BBB was disrupted, and ICP elevation persisted. Thus, it is thought that 20 minutes is the ischemic time threshold for brain damage. When ischemic time was increased to more than 6 hours, the extent of the infarcted area markedly increased (P＜0.05), with induction of hemorrhagic infarction and severe brain damage. It is desirable that circulatory reconstruction procedures during the acute stage of cerebrovascular occlusive disease be performed within 4 hours of onset. In this MCA occlusion model in cats, there were strong correlations between the degree of disturbed vessel reactivity, state of BBB disruption, level of ICP elevation and extent of infarcted area.