低剂量伽玛刀照射对癫痫大鼠皮层及海马NMDA受体亚基表达的影响

Effects of low dose of gamma knife irradiation on the expression of NMDA receptor subunits in thecortex and hippocampus of epileptic rats

目的观察低剂量伽玛刀照射对癫痫大鼠皮层和海马N-甲基-D-天氡氨酸(N-methyl-D-aspartate,NMDA)受体亚基表达的影响。方法根据动物是否致痫及接受伽玛刀照射,将大鼠分为4组:对照组、伽玛刀组、药物致痫组、伽玛刀+药物组。腹腔连续注射戊四氮(pentylenetetrazole,PTZ)制备癫痫大鼠模型,以双侧额叶为照射靶区对大鼠进行低剂量伽玛刀照射,边缘剂量为15Gy。观察并记录各组大鼠伽玛刀照射前、后癫痫发作情况,并于伽玛刀照射后12周后留取脑组织,分别利用免疫组化及免疫蛋白印迹法对大鼠皮层及海马NMDA受体亚基NR1、NR2A和NR2B进行检测。结果对照组及伽玛刀组大鼠无痫性发作表现,与药物致痫组大鼠相比,伽玛刀+药物组大鼠经低剂量伽玛刀照射后12周,痫性发作明显减轻(P<0.05)。与对照组相比,药物致痫组大鼠额叶皮层及海马CA1、CA3区NR1、NR2A和NR2B表达均明显增强(P<0.05),阳性神经元数目及平均吸光度值均明显增加(P<0.05);与药物致痫组比较,伽玛刀+药物组额叶皮层及海马CA1、CA3区NR1、NR2A和NR2B表达均明显降低(P<0.05),阳性神经元数目及平均吸光度值明显减少(P<0.05);伽玛刀组与对照组无明显差别(P>0.05)。结论癫痫大鼠额叶皮层及海马NR1、NR2A及NR2B亚单位蛋白表达增强,低剂量伽玛刀照射可能引起癫痫大鼠皮层及海马NMDA受体亚基表达减少,这可能是低剂量伽玛刀抑制癫痫发作的分子机制之一。

Objective To investigate the effects of low dose of gamma knife irradiation on the expression of N-methyl-D-aspartate (NMDA) receptor subunits in cortex and hippocampus of epileptic rats.Methods The rats were randomly divided into 4 groups: control group,GK group,pentylenetetrazole (PTZ) group and GK+ PTZ group.The rats were injected intraperitoneally with PTZ to establish the epileptic models.Gamma knife irradiation was performed on bilateral frontal cortex of rats at a peripheral dose of 15Gy.After irradiation,the changes of the seizure and behaviors were observed and recorded.The rats were killed on the 12th week after irradiation,Immunohistochemstry and western blotting were used to detect the relative expression levels of NMDAR subunits (NR1,NR2A,and NR2B) in the cortex and hippocampus.Results There were no epileptic seizures in the control group and the GK group.Compared with the PTZ group,the epileptic seizures of rats in the GK+PTZ group were significantly reduced after low dose gamma knife irradiation (P<0.05).Compared with control group,the protein expression levels of NR1,NR2A and NR2B in the PTZ group increased significantly in the cortex and hippocampus,and so were the positive neurons and their average absorbance value (P<0.05).Compared with PTZ group,the protein expression levels of NR1,NR2A and NR2B of the GK+PTZ group decreased remarkably in the cortex and hippocampus (P<0.05).Protein expression levels of NR1,NR2A and NR2B were not significantly different between control group and GK group (P>0.05).Conclusion Epileptic rats exhibited an increase in the protein expression levels of NR1,NR2A and NR2B in the cortex and hippocampus while low dose of gamma knife irradiation can decrease expression levels of NMDA receptor subunits in the cortex and hippocampus of epileptic rats,which might represent a possible mechanism underlying the therapeutic effects of gamma knife irradiation on epileptic seizure.