X线照射对实验性癫痫大鼠脑皮层GABA和GABA_A受体的影响

A laboratory study on the effect of X-ray on GABA and GABAA receptors in cerebral cortex of epileptic rat

目的探讨癫痫大鼠放射治疗中γ-氨基丁酸(GABA)及其受体的作用机制并选择合理放射剂量。方法利用慢性点燃癫痫大鼠对照组、放射1组、放射3组进行0、24、6Gy的X线放射,对放射2组、放射4组和放射5组行12Gy的X线放射,每组10只,对照组和放射1组、放射3组于放射后1h断头取脑,放射4组于放射后1天、放射5组于放射后1周进行断头取脑,并观察放射5组其放射后癫痫发作情况,用氨基酸分析仪测定各组癫痫大鼠额叶皮层内的GABA含量变化,利用免疫组织化学方法观察抗GABAA受体阳性率。结果放射5组于照射后1周内癫痫在鼠未出现诱发癫痫发作。放射1组的GABA含量为(254.16±44.68)ng,GABAA受体阳性率为(39.56±7.22)%,均明显高于对照组,12Gy照射后1h、24h、1周后均较对照组间GABA含量高,其中以24h最为明显,分别为(252.09±33.89)ng,(348.73±56.00)ng和(258.02±62.95)ng。抗GABAA受体阳性率在照射后1周内基本稳定于较高水平。结论放射治疗癫痫主要是通过发生快速而持续的GABA与GABAA受体变化发生作用,癫痫大鼠接受12Gy的放射治疗较为合理。

Objective To investigate the role of GABA and GABAA receptor play in radiotherapy of epileptic rat, and to look for the appropriate dose of radiotherapy for epilepsy. Methods A chronic pentylenetetrazole chemical kindling rat model of epilepsy was reproduced, and the rats were divided for control group and radio groups 1 to 5 With 10 rats in each group. Control group, groups 1 and 3 were given 0, 24, or 6Gy X ray irradiation to the brain in turns, and groups 2, 4 and 5 were given 12Gy X ray irradiation, the rats in control group, groups 1, 2, and 3 were killed 1 hour, and group 4 was killed on day 1, and group 5 was killed in 1 week after radiotherapy. Content of GABA was measured by amino acid analyzer, and GABAA receptor changes were assessed by immunohistochemical staining in frontal lobe of the brain of rats in all groups. Seizure of rat in group 5 were recorded in 1 hour, 24 hours or 1 week after irradiation. Results The epileptic rats in group 5 didn＇t suffer from seizure after radiotherapy. In group 1, the quantity of GABA was （254.16 ± 44.68） ng, and positive rate of GABAA receptor was （39.56 ± 7.22） % , which were higher than those in control group, the content of GABA in rats received 12Gy X- ray radiotherapy were （252.09 ± 33.89）ng, （348.73 ± 56.00）ng and （258.02 ± 62.95）ng in lhour, 1day and 1 week after irradiation, and significant higher than that in control group, also, the positive rate of GABAA R in those rats were significant higher than that in control group. Conclusions The efficacy of radiotherapy for epileptic rat might be attributable to rapid and sustained change in GABA and GABAA receptors, and 12Gy appeared to be the appropriate irradiation dose for epileptic rat.