[Focal cerebral infarction in the rat: I. Operative technique and physiological monitorings for chronic model].

The purpose of this paper is to develop a new chronic model of focal cerebral infarction by occluding the middle cerebral artery (MCA) in the rat. The operative method and results of physiological monitoring before, during, and after operation are shown. In adult male Sprague-Dawley rats, the left MCA was occluded via trans-retro-orbital approach simply by retracting the temporalis muscle. This method was slightly modified from our original method for chronic experiments. In a group of rats, systemic arterial pressure and blood gases were monitored using a femoral arterial catheter before, during, and after the operation. In the other group, blood pressure by tail-cuff method, neurological findings, and body weight were examined for one week after the MCA occlusion. During the operation under the halothane anesthesia, systemic arterial pressure decreased about 30% comparing with preanesthetic normal value and then quickly returned to normal within 30 minutes after the operation. Body weight progressively decreased in the occluded group during the observation period of one week, although body weight in the sham-operated group decreased only for initial few days and recovered. No animal died during first one week. Slight right hemiparesis was observed only in the MCA occluded group for few days.