[Pathological and pathophysiological studies on central nervous system in experimental cerebral ischemia of the rat].

The present study was undertaken to elucidate the pathological and pathophysiological characteristics of experimental cerebral ischemia in rats. The purpose of this study was also to clarify whether this animal model is useful for the research of multiple cerebral infarction. In order to create a cerebral ischemia model, arterioles were embolized by injecting 2000 carbon-microspheres (50 microns in diameter) into the right internal carotid artery of ketamine anesthetized rats. Pathological studies and pathophysiological evaluations were performed by electrocorticography (ECoG) and by measuring regional cortical blood flow (CBF) in embolized rats. An attempt was also made to examine learning ability: embolized rats were subjected to the passive avoidance test. Pathophysiological studies revealed most microspheres to be located in the ipsilateral hemisphere with a few in the contralateral hemisphere. Most foci of cerebral infarction were distributed in the area fed by the ipsilateral middle cerebral artery and the anterior cerebral artery, while a few of them were found in the area fed by the contralateral anterior cerebral artery. Regions of cerebral infarction consisted of microcerebral infarctions, some of which were fused to each other. The pathological characteristics of this experimentally induced cerebral ischemia were those of multifocal cerebral infarction. Both ECoG and CBF decreased after injection of carbon-microspheres, and these two parameters did not recover for more than 60 min in both hemispheres. Seven days after cerebral embolization, the shortened response latency in the passive avoidance test, possibly indicating memory impairment, was observed. Our findings suggest that cerebral ischemia of the rat produced by carbon-microspheres (50 microns in diameter) is useful in the pathophysiological investigation of multiple cerebral infarction.