[Experimental study on brain reversibility following temporary regional cerebral ischemia; from the point of view of vessel behavior and histological changes].

Using a middle cerebral artery occlusion model in adult cats, we investigated the ischemic time threshold for inflicting damage on cerebral vessel behavior and brain tissue. With the transorbital approach, a middle cerebral artery (MCA) was exposed and temporarily obstructed by a Zen's clip. Animals were divided into ten groups (each group: N = 8) according to the ischemic time of 10, 20, 30 minutes, 1, 2, 4, 6, 8, 12, 24 hours. Five hours after the recanalization, Evans' blue dye was injected intravenously and after further 30 minutes, the brain was fixed with transaortal perfusion for histological examinations. A cranial window was made above the ectosylvian gyrus which has poor anastomosis. The pial vessel behavior was observed through the cranial window and evaluated using an intravital microscope and a videoangiometer. Considering the correlation between functional change of vessel behavior and pathological change in the brain, the threshold time of ischemia inflicting irreversible damage was estimated. In the 30 minute ischemia group, deterioration of vessel behavior began to be observed as well as extravasation of Evans' blue dye. As the ischemic duration became longer, infarction and hemorrhage, which showed close correlation, increased. When the duration of ischemia was 6 hours, the infarcted area was significantly larger than that of the 4-hour ischemia group. Intracranial pressure (ICP) markedly increased as soon as recanalization took place. We think this phenomenon is due mainly to swelling. About three hours after recanalization, ICP further increased due to severe vasogenic edema in addition to the brain swelling.(ABSTRACT TRUNCATED AT 250 WORDS)