二硫化碳暴露对大鼠学习能力的影响

Effects of carbon disulfide on the learning ability of rats and its underlying mechanisms

目的构建大鼠二硫化碳染毒学习损伤的动物模型,观察其海马组织的病理学改变,并探讨其中枢神经损伤的原因与机制。方法 80只雄性Wistar大鼠随机分为正常对照组,低、中、高剂量二硫化碳组,每组20只,将二硫化碳溶于玉米油中,经口给予大鼠,染毒剂量分别为200、400和600 mg/kg,正常对照组给予等体积的溶剂,连续20 d。染毒第16天起,采用Morris水迷宫检测动物的学习能力。实验结束后,每组随机选取10只经心脏灌注固定,制作大脑冰冻切片,采用Nissl染色及免疫组织化学法分别观察大脑海马神经元的形态学及神经元数量变化。其余10只海马进行一氧化氮(NO)含量和一氧化氮合酶(NOS)活性检测。结果二硫化碳染毒导致中枢神经系统损伤,水迷宫实验中的游泳总路程和逃避潜伏期呈现剂量依赖性延长(P<0.05)。中、高剂量二硫化碳组海马CA3和DG区神经元体积增大、着色浅、细胞排列紊乱;神经元特异标志核蛋白抗体免疫染色结果显示,中、高剂量二硫化碳组与正常对照组相比,海马CA3区神经元细胞数目明显减少(P<0.01);生化检测结果显示,中、高剂量二硫化碳组海马NO含量和NOS活性明显增高。结论二硫化碳暴露可导致神经系统功能障碍和海马神经元损伤,并可能与其影响NOS活性,使脑内NO代谢紊乱,发生氧化应激有关。

Objective To develop an animal model illustrating the effects of carbon disulfide exposure on learning ability,to detect the pathological changes of the hippocampus caused by carbon disulfide exposure,and to reveal its underlying mechanisms. Methods A total of 80 Wistar rats were randomly divided into 4 groups： control,low,medium and high dose groups,followed with the treatment of corn oil,200,400 and 600 mg / kg of carbon disulfide,respectively,by gavage daily for 20 days. The learning ability of the rats was tested from day 16 to 20 with Morris Water Maze. The pathological changes of the hippocampus was detected with Nissl staining and immunohistochemical staining. The level of nitric oxide（ NO） and activity of nitric oxide synthase（ NOS） were measured with biochemical assay kits. Results The swimming distance and escape latency of the carbon disulfide-treated rats increased（ P〈0. 05） compared to those of the control group,in a dose-dependent manner. The neurons in the CA3 and DG area of hippocampus were found with increased size,lighter color,and disordered cell arrangement in Nissl staining. The neural nuclei（ Neu N）staining showed a significant loss of neurons in CA3 region of the 600 mg / kg carbon disulfide treated animals compared to the control group（ P〈0. 01）. The further detection on the level of NO and activity of NOS in the hippocampus showed an increase in the medium and high dose group rats. Conclusion Exposure to carbon disulfide could cause neuronal loss in the hippocampus CA3 region,resulting in learning incapability of the exposed animals. The underlying mechanisms of the neuronal damage might be attributed to NO and NOS change in the hippocampus.