Reperfusion Models of Rat Middle Cerebral Artery Occlusion:Extracranial and Transcranial Methods

ABSTRACT

The author described a comparative study of 2 different experiemental methods of reperfusion models in rat;1) transcranial method(TC) and 2) extracranial method(EC). The transcranial method was performed by a direct approach to the middle cerebral artery(MCA) after temporozygomatic craniotomy in which a wire was hooked on the proximal portion of middle cerebral artery(MCA) and pulled it to make occlusion of MCA. For the extracranial method, a nylon surgical thread was inserted intraluminally along the internal carotid artery(ICA) to reach the anterior communicating artery. Recirculation of blood was accomplished by removal of the hook or of the thread after 4 hours occlusion of MCA. Two different models were subdivided into 4 chronological groupspre-reperfusion, 30 minutes, 2 hours, and 48 hours after reperfusion. The differences were evaluated with morphometric analysis after neutral red(NR) or tetrazolium salt(TTC) staining. From the evaluation of initial ischemic area, the extracranial method showed a larger infarct volume as compared to the transcranial method(p=0.013). Mean value(SD) of infracted area of EC and TC were 28.7%(4.4%) and 14.4%(8.1%) respectively. Recovery from the initial ischemia after reperfusion was gradually achieved in both of two groups(p<0.05). The restoration of blood flow after reperfusion was more rapid in EC group and only 2 hours' reperfusion was enough to show no difference between two methods. In TC group followed by 48 hours' reperfusion, 40% of animals resulted in gross infarction of MCA territory as noted with TTC stain, most probably due to reperfusion failure. EC group showed only one such a case(12.5%). But this difference was not in the range of significance statistically. From a technical point of view, EC was more simple, needed less time since a craniotomy was not performed, and required no manipulation of the brain or any intracranial vessels. From these results the author concluded that the extracranial method is a more reliable and technically more manageable one to be used as a reperfusion model for investigating the focal cerebral ischemia.