Abstract
The purpose of this study is to examine histological and behavioral changes following the bilateral carotid ligation in normotensive rats. Using male Sprague-Dawley rat, the bilateral common carotid arteries were permanently ligated under halothane anesthesia. One, 2 weeks, 1 month and 3 months after the carotid ligation, serial coronal sections of formalin-fixed brain were stained with H-E or Kluver-Barrela method and microscopically examined. For behavioral study, place navigation taks (Morris's water maze) and step-through type dark avoidance task were performed 1, 2 weeks, 1 month and 3 months after the ischemia. The survival rate within 48 hours after the carotid ligation was above 90% throughout the experiment. Among 46 survivors examined, 31 (67%) showed the development of ischemic lesions. The caudo-putamen was the most frequent site where ischemic lesion was observed in 26 rats (57%). The incidence of ischemic lesion in hippocampus, cerebral cortex or thalamus was 30%, 17% or 13% respectively. Post-operative place navigation taks showed transient impairment of spatial leaning/ memory, whereas pre-operative spatial memory was well preserved. Step-through type dark avoidance task revealed persistent impairment of acquisition and retention of dark avoidance reaction in the ischemic rats. These results indicate that bilateral carotid occlusion can cause considerable neuropathological and behavioral changes and thus may be a useful model for the study of mild global ischemia, particularly in its chronic stage.
