Protection of ischemic postconditioning from retinal ischeima reperfusion injury in rat

Background The potential protective effect of ischemia postconditiomng for hypoxia has been determined in many tissues and organs.But its mechanism in retina is still lack.Objective The aim of this study was to investigate the protective effect of ischemia postconditioning on retinal ischemia reperfusion injury.Methods Thirty-six health male Wistar rats were randomized into the normal control group,sham group,ischemia reperfusion group and ischemic postconditioning group.Retinal ischemia reperfusion models were induced by elevating the intraocular pressure to 110 mmHg for 60 minutes,and then the ischemic postconditioning was performed right away,1 minute and 10 minutes after ischemia in the rats of the ischemic postconditioning Ⅰ,Ⅱ,Ⅲ group,respectively.Electroretinogram (ERG) was recorded in the rats 7 days after operation,and the rats were sacrificed by excessive anesthesia.Retinal specimens were prepared for the histopathological examination.The retinal thickness and the recovery rates of ERG a,b waves and oscillation potentials (OPs) were compared among the groups using ANOVA of SPSS software.Results One day after experiment,the structure of rat retinas was nearly normal.However,retinal edema and vacuolar degeneration were seen in the rats of the ischemia reperfusion group and ischemic postconditioning Ⅰ,Ⅱ,Ⅲ groups primarily in the inner plexiform layer (IPL),inner nuclear layer (INL).The retinal thickness values of the entire layer,IPL and INL were significantly higher in the ischemia reperfusion group and ischemic postconditioning Ⅰ,Ⅱ,Ⅲ groups compared with the normal control group (all at P＜0.05).Seven days after experiment,the retinas were thinner in the rats of the ischemia reperfusion group than those of the rats in the sham group,but the retinal thickness values in the ischemic postconditioning Ⅰ,Ⅱ,Ⅲ groups were significantly increased in comparison with the ischemia reperfusion group (all at P＜0.05).In addition,the recovery rates of ERG a,b,OPs amplitudes were significantly lower in the ischemia reperfusion group and ischemic postconditioning Ⅰ,Ⅱ,Ⅲ groups compared with the normal control group (all at P＜0.05).However,the recovery rates of ERG a,b,OPs amplitudes evidently elevated in the ischemic postconditioning Ⅰ,Ⅱ,Ⅲ groups in comparison with the ischemia reperfusion group (all at P＜0.05).Conclusions Ischemia postconditioning can protect the structure and function of retina from ischemia reperfusion injury.Ischemia postconditioning plays the maximal effect immediately to 1 minute after ischemia reperfusion injury in Wistar rat. Key words: Retina;  Ischemia reperfusion injury;  Ischemic postconditioning;  Electroretinogram;  Retinal thickness