The Research Of Ischemic Postconditioning On The Time Window Following Ischemia-reperfusion

【Objective】:To approach the methods of chosing the suitable time window to ischemia/reperfusion of Ischemic postconditioning(IPC) through modeling the middle cerebral artery occlusion(MCAO) to rats by way of preparing the focal cerebral ischemia and reperfusion model,which may provide a new therapeutic strategy for clinical treatment thereby.【Methods】:The whole experiment was divided into 2 parts.1.To search the time window of ischemia-reperfusion.Rats of MCAO were randomly divided into 4 experimental groups and 8 rats for each.Supplying respectively reperfusion at 1,2,3, 4 hours after infarction,and respectively named as 1-hour group;2-hour group; 3-hour group;4-hour group;.The control group was marked as a group of permanent infarction.Each experimental group was compared for the differences of infarct volumes and neurological scores with the control group so as to find out the best time window of reperfusion.2.To ascertain the time window of postconditioning at postischemia,according to the best time window of reperfusion.The control group was the group of postconditioning in 2 hours after infarction.Experimental groups were divided into 7 groups and 8 rats for each.Supplying respectively reperfusion and immediate postconditioning at 3,4,4.5,6,12,24 hours after infarction(gave immediate reperfusion:block bilateral common carotid artery's blood flow for 10 seconds,then open for 10 seconds,repeated five times).Neurological function scores were tested at 1 hour and 48 hours,and then rats were executed for weighing water content of their brain tissues,calculating cerebral infarction volume and analyzing.【Result】:1.The first part of this experiment shows:the infarct volume in 2-hour group was obviously smaller than 3-hour group and the group of permanent infarction, while there was no marked difference in other groups(longer than 3-hours) and the group of permanent infarction,and after the staining we found out that if reperfusion was given in 4 hours,the infarct volume varies directly with infarct time.The initial result of the time window of ischemia-reperfusion is 3 hours.2.The second part of this experiment shows:the infarct volume,the extent of cerebral edema of the group of postconditioning in 4.5 hours after infarction is apparently smaller than the group of postconditioning in 2 hours after infarction. while there was no marked difference between the group of postconditioning in 4.5 hours and the group of postconditioning in 2 hours in neurological function scores not only after 1 hour reperfusion but also after 48hours reperfusion.【Conclusion】:1.Ascertaining initially the time window of ischemia-reperfusion in rats is 2 hours;2.If reperfusion was given in 4 hours,the infarct volume varies directly with infarct time;3.Searching initially the time window of postconditioning at postischemia is 4.5 hours,but as the time lengthens,the death rate of rats increased obviously.