目的：了解缺血缺氧性脑损伤(HIBD)后24h内脑组织活性Caspase-3表达的动态变化。方法：7d龄SD大鼠随机分为正常对照组和HIBD组 ，HIBD组分别观察到缺血缺氧后3h，6h，12h，24h。以免疫组化及Western Blot方法观察各组活性Caspase-3的表达。结果：随时间推移缺血缺氧后24h内活性Caspase-3阳性染色由细胞质性转向细胞核性，活性Caspase-3阳性染色细胞明显皱缩。HIBD组受损侧枕部皮质区活性Caspase-3阳性细胞数于缺血缺氧3h增多，6h有所下降，12h再次增多，并于24h达高峰，均高于正常对照组(P<0.05 或 0.01)；海马回CA1区 活性Caspase-3阳性细胞数则随时间延长而增多，并于24h达高峰，均高于正常对照组(P <0.01 或 0.05)。Western Blot方法亦示HI后3h开始损伤侧脑组织中出现Caspase-3表达，6h时表达减弱、12h再次增高。结论：以活性Caspase-3作为HIBD导致脑细胞凋亡的指标，可观察到HIBD后24h内凋亡二次增多的动态变化现象，为掌握 抗凋亡制剂治疗HIE 的时机提供了一定的依据。

OBJECTIVE: To study the change of cleaved Caspase-3 expression within 24 hs following hypoxia ischemia brain damage (HIBD) in neonatal rats. METHODS: Seven day old rats were randomly assigned into control group and HIBD group. The Caspase-3 expression was assayed by the immunohistochemical staining and Western Blot analysis at 3, 6, 12 and 24 hs after hypoxia ischemia (HI). RESULTS: The positive staining of Caspase-3 transferred from cytoplasm to the nuclei and the cells were apparently condensed and shrunk within 24 hs after HI. The number of the cleaved Caspase-3 positive cells in the damaged cortex increased at 3 h, decreased at 6 h, increased again at 12 h and peaked at 24 h after HI, whereas the number in the damaged hippocampal CA1 region increased with time and peaked 24 hs after HI. The number of the Caspase-3 positive cell both in the cortex and the hippocampal CA1 region of the HIBD group at 3 h, 6 h, 12 h and 24 h was greater than that of the control group (P< 0.05 or 0.01 ). Caspase-3 expression was also found in the damaged brain tissue 3 hs after HI by Western blotting analysis. The intensity of the expression, decreasing at 6 h but increased again 12 hs after HI. CONCLUSIONS: The character of brain cell apoptosis within 24 hs following HIBD, increase of apoptotic cells twice, may be found with Caspase-3 as the marker for evaluating brain cell apoptosis in HIBD and it may be as reference for using anti apoptotic agents in treatment of HIE.