清醒状态下大鼠放射性脑损伤实验模型的建立

The Establishment of Brain Radiation Injury Experimental Model of SD Rats with Whole Brain Irradiation in Wakefulness

目的 排除麻醉药物对实验结果的干扰 ,建立清醒状态下全脑照射大鼠放射性脑损伤实验模型。方法 将SD大鼠随机分为 2Gy、15Gy、30Gy剂量照射组和假照射组 ,每组 2 5只。自制“热记忆膜固定罩”固定大鼠照射体位 ,4MeV电子线作不同剂量的单次全脑照射 ,并用治疗束流分析仪和剂量仪作剂量学监测。在照射后 1个月内每周 2次 ,观察并记录大鼠头部照射野毛发与皮肤的情况以及体重的变化 ,并进行神经行为学评分。观察大鼠在照射前、照射后 6h、1d、1周和 1个月时海马CA1区神经细胞的病理形态学改变。结果 该照射条件下的最大剂量点深度约为 14 .3mm ,各照射点吸收剂量的差异≤ 5 %。在通过“热记忆膜固定罩”后 ,剂量衰减率≤2 .5 7%。全部 30Gy和部分 15Gy照射的大鼠在照射后约 2 0d出现照射野内脱毛现象 ,其余大鼠在观察期内无上述表现。各组别大鼠体重增长趋势和神经行为评分差别无显著性意义 (P >0 .0 5 )。病理观察显示放射性脑损伤程度与照射剂量、观察时间呈正相关 ,30Gy照射后随观察时间的延长 ,大鼠海马CA1区神经细胞逐步出现损伤和坏死。结论 该动物模型制作方法简便、可靠 ,排除了麻醉药物对实验结果的干扰 ,临床模拟性好 。

Objective To establish the brain radiation injury experimental model of Sprague-Dawley (SD) rat being irradiated in wakefulness so that the side effects from the anesthetics can be eliminated. Methods Experiment animals were divided into 4 groups randomly according to the difference of radiation dose. Each group involved 25 rats. “Thermoplastic material fixing cage” was used to keep rats in wakefulness during irradiation. The whole brains of SD rats were irradiated by 4MeV electron beam at a single dose of 0 Gy,2 Gy,15 Gy and 30 Gy,which was measured by therapy beam analyser and dosimeter. The scores of gross neurological symptoms and changes in body weight were sequentially evaluated twice every week after irradiation. The examination of the head skin inside the field was performed as well. The changes of the nerve cell in the hippocampus region of rats with the Hematoxylin-eosin (HE) staining were observed at the time of 6 hours、1 day、1 week and 1 month after irradiation. Results The peak dosage depth of 4MeV electron beam was 14.3mm,and the dosimetry homogeneity of the radiation field was within 5%. The dose attenuation rate was less than 2.57% because of the thermoplastic material fixing cage. Intra-portal alopecia was observed in all the rats ex-posed to radiation at the dose of 30 Gy and in some of the rats exposed to radiation at the dose of 15 Gy. There was no significant difference in increasing trend of body weight and the score changes of the gross neurological symptoms in all groups. The obvious lesion was observed in the hippocampus region of rats after 30 Gy irradiated. Conclusion The brain radiation injury experimental model of SD rat in wakefulness with whole brain radiation eliminates the side effects from the anesthetic. It appears to be an excellent model for studying on the brain radiation injury in the early stage.