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Aim: To investigate the time window of the brain protective role of limb ischemic preconditioning (LIP) in CA 1 hippocampus in brain ischemic reperfusion model of rats.Methods: Fifty Wistar rats whose bilateral vertebral arteries were occluded permanently were randomly assigned to sham, brain ischemia, sham LIP and LIP +brain ischemia groups.The LIP + brain ischemia group was further divided into LIP 0 h, 1 h, 3 h, 6 h, 12 h, 1 d and 2 d groups according to the time of reperfusion after LIP Histological changes of the hippocampus were evaluated using thionin staining by neuronal density (ND) and histological degree (HG).Results: Brain ischemia induced significant damage of the neurons, HG was increased and ND was decreased compared with sham group.The damage was prevented by LIP 0 h, 1 h, 3 h and 6 h prior to brain ischemia, which is represented by the decrease in HG, and increase in ND compared with brain ischemia group.HE staining also presented the similar trend with thionin results.Conclusion: These results showed that LIP plays important brain protective role, in whose LIP immediately before brain ischemia is most obvious.