Abstract: Objective To investigate the periodic quantity variation of proliferating neuronal progenitors after global brain ischemia and provide evidence for choosing the time-window of drug therapy to promote neuronal regeneration after ischemia.Methods Adult male Wistar rats were subjected to 15-min global brain ischemia(four-vessel occlusion model)and randomized subsequently into 8 groups(n=3).The rats were given intraperitoneal injections of BrdU(75 mg/kg)for 4 times daily(at a 2-hour interval)since day 7 till day 11 after ischemia,and on day 29,the rats were perfused transcardially for fixation.Another 3 normal rats were given BrdU in the same manner and killed the next day.Coronal sections of the brain tissue(30 μm)were prepared for immunocytochemical detection of BrdU-labeled cells and immunofluorescent detection of BrdU/NeuN double-labeled cells.The density of BrdU-positive cells and BrdU/NeuN double-labeled cells in the hippocampal dentate gyrus(DG)and CA1 region were counted and the density of proliferating cells at different days after ischemia were compared using one-way ANOVA.Results The proliferation of the neuronal progenitors increased after global brain ischemia.The number of BrdU-positive cells in the DG and CA1 region decreased gradually in 7-10 days after ischemia,and reached the normal level during 11-14 days.The differentiation of the progenitors did not vary after ischemia.Conclusion Increased proliferation of the neuroprogenitors occurs mainly within the initial 10 days after global ischemia in rats.