全脑照射对迟发性脑损伤大鼠学习记忆能力和海马突触结构的影响

The changes of learning-memory ability and synapse of hippocampus in delay brain injuries rats after whole brain irradiation

目的 探讨放射线全脑照射对大鼠迟发性脑损伤后学习记忆能力和海马突触结构的影响.方法 分组采用直线加速器对SD大鼠进行全脑照射,剂量分别为20 Gy和30 Gy.在照射前和照射后120d分别进行Morris水迷宫实验,分析各组大鼠行为学检测结果 ,采用平均逃避潜伏期和搜索策略两个指标评价大鼠学习记忆能力;同时用电镜和计算机图像分析仪观测模型鼠海马CA3区Gray Ⅰ型突触界面结构参数的变化.结果 20 Gy照射后120 d平均潜伏期为（41.17±10.76）s,搜索策略得分（27.13±2.34）分,30 Gy照射后120d平均潜伏期为（78.49±9.32）s,搜索策略得分（16.52±2.71）分,均与照射前及对照组差异有显著性.20 Gy照射后120 d海马突触后膜厚度为（22.03±6.84）nm,30 Gy照射后120 d海马突触后膜厚度为（23.19±7.65）nm,与放射前及对照组比均差异有差著性（P＜0.05）.同时还观察到20Gy和30Gy照射后均较对照组突触活性带长度短,突触界面曲率小,突触间隙宽度变窄（P＜0.05）.结论 迟发性放射性脑损伤后学习记忆能力下降,并且可能与海马突触病理改变有关.

Objective To study the changes of learning-memory ability and synapse of hippocampus after radiation injuries. Methods Sprague-Dawley rats were grouped according to radiation dose to 20Gy group,30Gy group radiated by linear accelerator and control group were used before radiation and 120 days after radiation. Morris maze test were taken to study the learning and memory ability of rats in each group. Average escape latency and search strategy were scaled and analyzed in each group. The parameters of synapse in CA3 area of hippocampus were studied by using electron microscope and image analyzer. Results AEL of 20Gy group was （41. 17 ±10.76 ） s and score of SS was 27.13 ± 2.34 after 120 days＇ radiation but AEL of 30 Gy group was （78.49 ± 9.32）s and the score of SS was （23.19 ± 7.65 ） nm. There were significant statistic differences Compared with control group and before radiation （P 〈 0.05 ）. The thickness of PSD of 20 Gy group was （ 22.03 ± 6.84 ） nm after 120days＇ radiation and （23.19 ± 7.65 ）nm in 30 Gy group. There were significant statistic differences compared with control group and before radiation. It was observed that both in 20 Gy and 30 Gy group＇ s the length of synaptic activity area was shorter,the curvature of synaptic interface was smaller,the width of synaptic cleft and the thickness of PSD was narrower than that of control group. Conclusion There was close relation between the changes of learning-memory ability and synapse of hippocampus after radiation injuries.