亚低温对大鼠脑缺血再灌注后出血转化及超微结构的影响

目的 观察亚低温对不同时间窗缺血再灌注大鼠出血转化的影响及脑组织超微结构的改变，探讨亚低温对局灶性脑缺血大鼠的神经元和血管的保护作用。方法 利用线栓法制作SD大鼠大脑中动脉缺血再灌注（middle cerebral artery occlusion-reperfusion，MCAOR）模型，闭塞时间分别为3 h、6 h和9 h，再分别随机分为常温组、3 h和5 h亚低温组，并设立假手术组。其中亚低温组再灌注后，用10％水合氯醛再次麻醉大鼠，将大鼠置于冰毯上降温，在15分钟内将大鼠肛温降至亚低温状态（32℃～35℃），保持大鼠亚低温状态3 h或5 h。再灌注24 h后处死大鼠并取脑。每组取6只大鼠测量各组脑出血量；每组取2只大鼠，透射电镜下观察大鼠视交叉后皮层缺血边缘带神经元和内皮细胞的形态学变化。结果 各MCAOR组大鼠随缺血时间延长出血转化量增加，应用亚低温干预后，各组出血转化量均减少。各MCAOR组大鼠视交叉后皮层缺血边缘带超微结构显示不同程度受损，随着缺血时间延长逐渐加重。亚低温可减轻其损伤程度，以缺血3 h亚低温3 h组效果最好。结论 亚低温对大鼠缺血再灌注后脑组织具有保护作用，改善脑组织超微结构，为脑功能重建提供超微结构基础。

Effects of Subhypothermia on Hemorrhagic Transformation and Ultramicrostructure after Middle Cerebral Ischemia-Reperfusion

Objective To investigate the effect of sub-hypothermia on hemorrhagic transformation and ultra- structure of the rats with cerebral ischemia-reperfusion within or beyond 3 hours-the therapeutic time window, and to study the neuroprotective effect of subhypothermia on cerebral ischemia in rats. Methods Using the intra-luminal suture method, we subjected Sprague-Dawley rats to middle cerebral artery occlusion（MCAO） model and reperfusion 3 hours, 6 hours or 9 hours later, and then the rats were divided into normal temperature group, subhypothermia for 3 hours group and subhypothermia 5 hours group. A group of sham-operated animals without ischemic was used as control. At the 24th hour after ischemia, all rats were killed. Six rats were selected in each group for measuring the amount of bleeding according to the method described by Sumii T et al. Two or 3 rats were selected in each group for observing morphologic changes of endothelial cell, gliacyte, neuron and neuropile in retrochiasmatic cortex ischemic boundary zones by electron microscopy. Results The cerebral injury and hemorrhagic transformation aggravated as the time prolonging after ischemia-reperfusion,subhypothermia should prevent the development of the injury and hemorrhagic transformation. Observation under transmission electron microscopes showed that cerebral ultrastructure of retrochiasmatic cortex ischemic boundary zones was damaged in different degrees in MCAOR groups, and the cerebral ultrastructure injury increased in cortex ischemic boundary zones as the ischemic time prolonging. Subhypothermia could alleviate the nerve cell damage. It showed the most effective in MCAO3hR＋HT3h group. Conclusion Subhypothermia has protective effect on brain ultrastructure of rats with cerebral ischemia reperfusion injury. It provides ultrastructural foundation for brain functional reconstruction.