MIDDLE CEREBRAL-ARTERY OCCLUSION IN WISTAR AND FISCHER-344 RATS - FUNCTIONAL AND MORPHOLOGICAL ASSESSMENT OF THE MODEL

Cerebral infarction volume after occlusion of a short proximal segment of the middle cerebral artery (MCA) is reported to be different in Wi star compared to Fischer-344 (F344) rats, in both size and variability . Knowledge about the cause of these differences might enable us to ex plain and perhaps reduce the variation in infarct volume and create a reproducible model of focal cerebral ischemia in the rat. We investiga ted in Wistar and F344 rats both the effect of occlusion of a long pro ximal MCA segment on cerebral infarction volume, visualized by magneti c resonance imaging and histology, and the morphology of the major cer ebral arteries. Occlusion of a long proximal MCA segment resulted in a striatal and a small cortical infarction in Wistar and a striatal and sizable cortical infarction in F344 rats (as is the case after occlus ion of a short proximal MCA segment). In Wistar rats, however, occlusi on of a long proximal MCA segment strongly reduced the variability in infarction volume in comparison to occlusion of a small proximal MCA s egment. Analysis of the morphology of the major cerebral arteries show ed a significantly higher number of proximal side branches of the long proximal MCA segment in Wistar rats than in F344 rats. We conclude th at after short-segment proximal MCA occlusion, extreme variability in cerebral infarction volume in Wistar rats compared to F344 rats may be attributable to a significantly greater number of proximal MCA side b ranches in Wistar rats than F344 rats.