目的 :探讨半脑照射后大鼠的海马神经元密度变化规律。方法 :采用 4Mev的电子束对 8～ 10周龄的雌性SD大鼠作半脑照射 ,照射剂量分别为 5、15、3 0Gy。另设对照组 (只麻醉 ,不照射 )。于照射后第 3天 ,1、3个月分别计数海马CA2区神经元密度。结果 :照射后海马神经元密度呈下降趋势 ,3 0Gy照射组有统计学差异。结论 :半脑照射可使大鼠的海马神经元密度下降 ,海马神经元密度程度与照射剂量有关。 Objective: To investigate the changes of neuron densities in hippocampus of rats after hemi-brain irradiation. METHODS: Female SD rats aged 8-10 weeks old were irradiated with 4 Mev electron beam at the doses of 5, 15 and 30 Gy, respectively. Another control group (anesthesia, no irradiation). On the 3rd day and the 1st and 3rd month after irradiation, the neuronal density of hippocampus CA2 area were counted respectively. Results: The density of hippocampal neurons decreased after irradiation, and there was a significant difference between 3 Gy and 0 Gy groups. Conclusion: The hemi-neuron densities in the hippocampus of rats decreased after irradiation with hemi-brain, and the density of hippocampal neurons was related to the dose of irradiation.