Abstract
The middle cerebral artery of dogs was occluded by a clip and the collateral blood supply was compromised by subjecting to hemorrhagic hypotension for 1 hour. Following restoration of the systemic blood pressure by infusion of the shed blood, the clip was permanent and removed at to different times. The first group represented animals which were kept MCA clipped for 24 hours (permanent occlusive group). In the second group, MCA clip was removed after 24 hours, then the involved area was recirculated. The third group was removed MCA clip after 4 hours and thereafter was recirculated for 20 hours in the involved area.
After 24 hours in the gray and white junction of ischemic area, hemorrhage from severe iscmemic damaged venules was observed in the three different groups. While in the iscmemic cortex, capillaries of the first two groups were packed with erythrocytes and platelets, but were not broken down. In the third group, hemorrhage cccured from the necrotic capillaries which were accompanied with the tapering and discontinuity of the endothelium and the destruction of the basement menbrane.
In our models, the last two groups as compared with permanent occlusive group were developed more severe ischemic damage by restoration of the blood flow. In the second group, strongly increased hemorrhage occured in the gray and white junction. The third group was increased brain edema and also occured hemorrhage in the ischemic cortex.
