AIM AND METHODSTo investigate the role of the duration of ischemic preconditioning and the interval between the ischemic preconditioning and the following injured ischemia in induction of ischemic tolerance of the hippocampus, using 4 vessel occlusion (4VO) global ischemic model of rats.

RESULTSIschemia for 6 min resulted in a apparent delayed neuron death (DND) in the hippocampus, while ischemia for 3 min did not cause DND in the hippocampus. Ischemic preconditioning for 3 min could apparently decrease DND caused by ischemia for 6 min followed the preconditioning at intervals of reperfusion 1 or 3 d (P < 0.01), indicating the protective effect of the ischemic preconditioning against the following severe ischemia. However, ischemic preconditioning for 1 min did not produce any apparent protective effect. The DND could not be decreased not only, but increased in a condition of ischemic preconditioning for 5 min followed by 6 min injured ischemia at a interval of 1 d or ischemic preconditioning for 3 min followed by ischemia for 6 min at a interval of 1 h.

CONCLUSIONGlobal ischemic preconditioning could induce tolerance of the hippocampus to ischemic injury. The proper duration of ischemic preconditioning and the interval between the preconditioning and the following injured ischemia might be 3 min and 1 to 3 days, respectively, in the 4VO rat model.