Prolonged Ischemic Cerebral Infarct in the Rat after Middle Cerebral Artery Occlusion: Part 1:Evolution and Time Course of the Infarction

Park, Chun Kun; Jung, Chul Ku; Kim, Dal Soo; Kim, Moon Chan; Kang, Joon Ki

Abstract

Although evolution and time course of ischemic brain infarct should be a matter of interest to investigators in the research of brain ischemia as well as traumatic brain injury, few papers have ever been reported. Authors observed quantitatively sequential changes of infarct size and regional cerebral blood flow(rCBF) to assess the evolution of focal ischemic brain infarct in the rat following left MCAO. Fifteen rats, weighting 250 g to 370 g, were used in this experiment. The experiment animals were divided into three groups: 6, 24 and 48 hours groups(HG) after MCAO. The rCBF of bilateral caudate nuclei was measured by hydrogen clearance methods. Areas of brain infarction were delineated by tripheny-tetrazolium chloride(TTC) at the preselected 8 coronal levels of forebrain. The areas of brain damage were drawn on scale diagrams(x4 actual size) of forebrain and measured by a plannimeter. In the experimental groups, just after MCAO, rCBF of the ipsilateral caudate nucleus was reduced to 29.4+/-6.5 to 24.5+/-7.9 ml/100 g/min from the basal value of around 117 to 121 ml/100 g/min and showed a tendency of getting more reduced to 19.4+/-7.6 ml/100 g/min by 48 hours. The rCBF of the contralateral caudate nucleus was maintained in the basal value throughout the experiment. Comparing the total amounts of ischemic damage of 48 HG to those of 5 and 24 HG, the infarction size was significantly increased in cerebral hemisphere as well as cerebral cortex and caudate nucleus(p<0.05). But there was not any significant difference between 6 and 24 HG. The experiment provides evidence for the evolution of focal ischemic brain infarct without any further change of decreased rCBF. The data suggest that it is desirable to observe the change of pathologic findings by not less then 48 hours following the arterial occlusion in the study of ischemic brain infarction in the rat, particularly as long as ischemic damage is delineated by TTC.