Effects of ischemic postconditioning on hippocampal neuroprotection in different cerebral ischemia models at the same "time window" in tree shrews

AIM: To compare the effects of ischemic postconditioning(PC) on hippocampal neuroprotection between thrombotic cerebral ischemia(TC) and middle cerebral artery occlusion(MCAO) models in tree shrews,and to explore the neural pretection mechanisms of PC at the same time windows.METHODS: The TC and MCAO models were established and ischemic PC was operated by cliped ipsilateral carotid artery of the animals 4 h after cerebral ischemia.The cortex infarct size was measured by 2,3,5-triphenyltertrazolium chloride(TTC) staining.The changes of neuronal ultrastructures and the regional cerebral blood flow(rCBF) in hippocampal CA1 area were observed 4 h,24 h and 72 h after cerebral ischemia by the method of electronic microscopy and laser Doppler technique,respectively.RESULTS: The mitochondria swelling,the cristae disorganizing and the expansion of endoplasmic reticulum were observed in hippocampal CA1 area after TC and MCAO.The infarct size and cell damage induced by MCAO were more severe than those induced by TC.The rCBF in hippocampus was significantly decreased after TC and MCAO.rCBF in TC group was markedly decreased at 24 h(P0.01) and rCBF in MCAO group was decreased at 72 h(P0.01) after cerebral ischemia.The improvement of hippocampal rCBF and reduction of mitochondrial damage by PC in TC group were more effective than those in MCAO group.CONCLUSION: Operation of PC at 4 h after cerebral ischemia has neuroprotective effects against cerebral ischemia injury.The protective effects of PC are more effective in TC model than those in MCAO model by improving rCBF in hippocampus.