Abstract: Objective: To investigate the dynamic changes in apoptosis of hippocampal neurons and nitric oxide content of hippocampal tissues at different time during global cerebral ischemia-reperfusion.Methods: Transient（15 min） global cerebral ischemia was induced by the four-vessel occlusion method invented by Pulsinelli,and reperfusion was instituted for 1,2,3,5,7 d respectively.The neuron apoptosis was identified and analyzed by DNA agarose gel electrophoresis and flow cytometry.Nitrate/nitrite(NO₃^-/NO₂^-) was assayed to represent nitric oxide content of hippocampal tissues.Results: DNA electrophoresis showed normal bands at 1d reperfusion,ladder pattern band representing apoptosis of neurons at 2 d and 3 d reperfusion.There was no ladder pattern band but bands representing necrosis of some neurons at 5 d and 7 d reperfusion.Flow cytometry showed that apoptotic rate of hippocampal neurons increased as reperfusion time extending and raised to the peak at 3 d reperfusion.Subsequently,apoptotic rate reduced gradually and returned to normal level at 7 d reperfusion.Nitric oxide content of hippocampal tissues increased significantly at 2 d reperfusion and peaked at 3 d reperfusion,then decline and returned to sham group level at（7 d） reperfusion.Conclusion: Both apoptotic rate of hippocampal neurons and nitric oxide content of hippocampal tissues showed dynamic changes after global cerebral ischemia-reperfusion.Two changes were consistent in the course of time.It is suggested that increasing in NO production maybe one of the factors inducing neuronal apoptosis.