| Objective To study the effects of ischemic postconditioning on cerebral ischemia/reperfusion and blood-brain barrier in rats following middle cerebral artery occlusion (MCAO),approach the methods of chosing the suitable time windows to cerebral ischemia/reperfusion.Method The whole experiment was divided into 2 parts.The first stageâ‘ To study the time window of ischemia/reperfusion.Rats of MCAO were randomly divided into 4 experimental groups and 8 rats each one.Supplying respectively reperfusion at 1,2,3,4 hours after iscemia and named as 1-hour group,2-hour group,3-hour group,4-hour group, the control group was marked a group of permanent infarction.Each experiment group was compared for the differences of infarction volumes and neurological scores with the control group so as to find out the best time window of reperfusion.â‘¡To ascertain the time window of postconditioning at postischemia according the best time window of reperfusion.The control group was the one of postconditioning at 2 hour after ischemia.Experimental groups were divided into 7 groups and 8 rats for each. Supplying respectively reperfusion at 3,3.5,4.4.5,5.5,12,24 hours after iscemia.Neurological functional scores were tested at 1 hour and 48 hour after ischemia,and then their brain tissues were executed for weighing water content,calculating cerebral infarction volume.The second stage(The current one)Ischemia/reperfusion model in rats was performed with suture method.15 rats were randomly divided into two groups:Reperfusion group at 2h after middle cerebral artery occlusion (R-MCAO)(n=7), Postconditioning group by transient bilateral common carotid artery occlusion/referfusion at 3.5h after middle cerebral artery occlusion(P-MCAO)(n=8).Neurological functional deficits were evaluated at 24h after ischemia/reperfusion.Rats were sacrificed at 24h after the reperfusion,their brains were obtained for TTC staining examination.While 16 rats were randomly divided into two groups:Reperfusion group at 2h after middle cerebral artery occlusion (R-MCAO)(n=8), Postconditioning group by transient bilateral common carotid artery occlusion/referfusion at 3.5h after middle cerebral artery occlusion(P-MCAO)(n=8). At 24h after the reperfusion, their brains were obtained for detecting collagen-IV and ZO-1 expression by immunohistochemistry method.Result (1)The infarction volumes in 2-hour group obviously were smaller than the one of the 3-hour and the permanent infarction groups,meanwhile there was no marked differences between other groups(longer than 3-hours) and the group of permanent infarction.The infarction volumes.the extent of cerebral edema of the group of postconditioning in 3.5 hours after infarction did not increase comparing to the one of postconditioning in 2 hour after infarction,while there was no marked difference between the group of postconditioning of in 3.5 hour and the one in 2 hour in neurological functional scores not only after 1 hour reperfusion but also after 48 hours reperfusion(p> 0.05).(2)Neurological functional outcomes by Ludmila test,Zea Longa test,over hanging test and open fild test, cerebral infarct size,the expression of collagen-IV and ZO-1 were not down-regulated by ischemic postconditioning(p>0.05) in I/R 24h as well. (3)In inclined planet test,the rats of P-MCAO group had worse neurologicalseverity performance than that of MCAO group(p<0.05).Conclusion (1)Ascertaining initially therapeutic time window of ischemia-reperfusion in rats is 2h.(2)Seaching therapeutic time window of postconditioning at postischemia in rats is 3.5h.(3)Ischemic postconditioning group in 3.5h after MCAO does not reduce neurological functional outcomes by Ludmila test,Zea Longa test,over hanging test and open fild test than ischemic reperfision group in 2h after MCAO.(4)Ischemic postconditioning increases neurological severity scores by inclined planet test.(5)Ischemic postconditioning group in 3.5h after MCAO does not increase cerebral infarct size comparing to ischemic reperfision group in 2h after MCAO.(6)Ischemic postconditioning up-regulates collagen-â…£,zo-1 of...
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