The Effects Of Ischemic Postconditioning On Cerebral Ischemia/reperfusion Injury In Rats

Objective To study the effects of ischemic postconditioning on cerebral ischemia and investigate the mechanism of postconditioning following middle cerebral artery occlusion in rats.Methods There are two part of experiment,one hundred and nine Sprague Dawley (SD)rats were used in the experiment.Primary part:We established the model of ischemic postconditioning and proved the protection of ischemic postconditioning for brain tissue.21 Rats were randomly divided into three groups:Control (ischemia/reperfusion),middle cerebral artery occlusion(MCAO)+transient unilateral common carotid artery occlusion(u-CCA-O),MCAO+transient bilateral common carotid artery occlusion(b-CCA-O)(n=7,respectively).Cerebral blood flow(CBF) was measured in different 15 time points:0min,10min after middle cerebral artery (MCA)occlusion,1h after MCA occlusion,0min after MCA reperfusion,10s of common carotid artery(CCA)occlusion and 10s ofCCA reperfusion in all five cycles, 30rain after MCA reperfusion.Rats were sacrificed at 48h after reperfusion and measured infarct size and brain edema;Functional neurological outcome was determined at lh and 48h after reperfusion.The second part:To investigate the protection mechanism of ischemic postconditioning.Eighty eight SD rats were randomized into 2 groups:Control group,MCAO+transient bilateral common carotid artery occlusion(b-CCA-O)group.At 4h,8h,24h,48h after the reperfusion,the brains were obtained for Matrix metalloproteinase-9(MMP-9)by immunohistochemistry and ELISA method.Used the in situ apoptosis detection kit (TUNEL staining)to detect the apoptosis neurons of cerebral(the junctional zone between cortex and basal ganglia)in rat(choose four rats of each group in random principle).Results 1.The results of CBF demonstrated that b-CCA-O group diminished 9% compared with Control and u-CCA-O group when 30 min after intervention.2.The rats of u-CCA-O and b-CCA-O group had better neurological performance at 1h after reperfusion(P＜0.05),the functional neurological outcome was improved by ischemic postconditioning.3.The Infarct volumes of u-CCA-O and b-CCA-O group diminished compare to the Control group(P＜0.05).4.TUNEL staining result:The TUNEL-stained cells of the b-CCA-O group were significant difference compare with the Control group,the number of the TUNEL-stained cells of b-CCA-O group diminished(P＜0.05).5.The brain edema of u-CCA-O group,b-CCA-O group diminished compare to the Control group(P＜0.05).6.The expression of MMP-9 of brain tissues in b-CCA-O group markedly diminished at basal ganglia compared to that of Control group.Conclusions 1.We established the method of cerebral ischemic postconditioning by MCAO model.2.Postconditioning which was formed by blocking unilateral common carotid artery temporary did not change the physiological index of rats.3.On 30min after MCA reperfusion,the number of CBF of b-CCA-O group diminished compare to the Control and u-CCA-O group.4.The cerebral infarct size and brain edema were obviously reduced by ischemic postconditioning.5.The functional neurological outcome was improved by ischemic postconditioning at lh after reperfusion.The score of neurological performance detected at 1h after reperfusion,so our experiment obviated restoration of neurological performance by them.6.Ischemic postconditioning blocked stroke-induced apotosis in the junctional zone between cortex and basal ganglia.7.The expression of MMP-9 was down-regulated by ischemic postconditioning.To sum up,Down-regulation of MMP-9 and stroke-induced apoptosis might be a key event in the molecular mechanism of ischemic postconditioning protection on brain.