Neuroprotection and optimal time window of ischemic postconditioning against cerebral ischemia reperfusion injury in rats

Objective To investigate the optimal time window of ischemic postconditioning(IP) against focal cerebral ischemia-reperfusion(I/R) injury.Methods Eighty male SD rats were randomly assigned into five groups: a sham-operated,a control and three IP(different time intervals: 15 s,30 s and 1 min).Focal cerebral ischemia model was established via middle cerebral artery occlusion(MCAO) with the intraluminal filament technique.The neurological deficit scores(NDS) were evaluated 24 hours after reperfusion.The apoptosis of brain cells and the levels of TNF-α in the hippocampal CA1 area were evaluated by TUNEL and immune stained method respectively.Results The behavioral tests showed IP attenuated neurological deficits after I/R.The NDS in the IP groups decreased significantly compared with the control group(P0.05),and the NDS in the IP 15s and IP 30s groups were lower than in the IP 1min group(P0.05).The number of surviving neurons increased significantly in the IP groups as compared with the control group(P0.05).IP significantly decreased the level of TNF-α in the hippocampal CA1 area compared with the control group(P0.05).The level of TNF-α was significantly higher in the IP1min group than in the IP 15s and IP 30s groups(P0.05).Conclusions IP could improve functional outcomes,decrease the expression of TNF-α and reduce the nerve cell apoptosis.The optimal time window of IP against cerebral I/R injury may be 15 s and 30 s.