A new experimental recirculation model for cerebellar hemisheric ischemia in the rat

Recently, both permanent and transient experimantal ischemic models have been reported using various laboratory animals. For the posterior fossa, there have been only a few ischemic models. This report describes a surgical approach in producing a new experimental recirculation model for cerebellar hemispheric ischemia in the rat. 1) At first, we made cast phenolic resin models of the vascular structure of the rat's brain. Using this model, we made an embolus by coating a 6-0 monofilament nylon thread with silicon rubber latex. 2) Adult male Wistar rats (300-350g) were anesthetized with pentobarbital sodium (40mg/kg). Through the median neck incision, cervical vertebral (C1-2 portion) were exposed. The transverse process of the second vertebra was carefully removed and the vertebral artery exposed for 3-4mm at the C1-2 level. Then, superior cerebellar artery (SCA) was occluded with the prepared embolic thread which was inserted 19mm into the vertebral artery. Next, the following studies were performed. (a) In one group, carbon black was perfused after 2 hours of ischemia. (b) In the other group, circulation in the superior cerebellar artery was restored by taking out the embolic thread after 6 hours of ischemia. Evans blue dye was then intravenously injected, and 2 hours agter recirculation, tissue was fixed by perfusion of formaline into the thoracic aorta. In all animals, gross brain was examined. In most of the SCA occluded animals, there was pallor of the cerebellar hemishper indicating failure of the carbon black perfusion. In the recirculation group, there was blue indicating damage of blood brain barrierd by Evans blue stain. These lesions revealed almost the same extension in both groups and were restricted to the cerebellar hemispher which, in the rat, is normally supplied by the superior cerebellar artery. These changes were detected in the cerebellar hemishper of 8 out of 19 rats. Our results appear to indicate that this model may be useful in the evaluation of pathophysiological states of cerebellar hemispheric ischemia and recirculation.