比较脑皮层不同部位电惊厥阈值与神经损害的实验研究

Electroconvulsive threshold and nerve damage in different parts of rat cerebral cortex

目的通过皮层不同部位的电刺激,测定大鼠惊厥阈值,比较各组皮层的惊厥阈值;观察比较各部位阈值稳定后的病理生理学改变。方法选择健康雌性SD大鼠,体重180~220 g,分别在额叶皮层、颞叶皮层、小脑皮层安放电极造模,作为刺激组,对照组仅安放电极不予刺激,使用直流电每日2次刺激大鼠额叶、颞叶、小脑皮层,当各刺激组阈值稳定后,采用SNK-q检验比较各组的皮层惊厥阈值,之后处死各组大鼠,用Nissl染色法观察海马神经元损害情况,同时计数各组大鼠海马区神经元数目,采用单因素方差分析中的SNK-q检验对各组神经元数目进行统计学比较。结果 (1)实验开始第1~2天时,大鼠三个刺激组皮层的惊厥阈值高,额叶皮层组阈值在1100μA上下,颞叶皮层组阈值在1200μA上下,小脑皮层组阈值在2100μA上下,随着刺激时间的延长,各组大鼠的皮层阈值持续降低,并最终稳定在一个基线水平,但其基线各不相同,额叶皮层组阈值波动于(511.00±10.97)μA左右,颞叶皮层组稳定在(440±12.46)μA左右,小脑皮层组稳定在(1300±53.63)μA左右,3组间进行比较,小脑与额、颞叶皮层组的阈值比较,差异有统计学意义(P<0.05),额、颞叶之间阈值比较,差异无统计学意义(P>0.05);(2)随着刺激时间的延长,刺激组大鼠脑海马CA3区神经元出现不同程度的丢失,排列紊乱,对照组高倍镜下观察神经元数目为(36.33±6.13)个,额叶皮层组、颞叶皮层组、小脑皮层组神经元数目分别为(22.79±1.01)、(17.78±1.40)、(26.00±1.70)个,与对照组相比,额叶、颞叶、小脑皮层组神经元个数较少,3组间比较差异具有统计学意义(P<0.05);(3)电刺激小脑皮层组时大鼠出现的症状与额、颞叶皮层组的表现不同,额、颞叶皮层组表现出典型的痫样抽搐,如点头、前肢及后肢抽搐及全身的强直阵挛等,而小脑皮层组表现为四肢、躯干的强直痉挛以及奔跑跳跃等。结论 (1)对于同样强度的电流刺激,颞叶与额叶皮层对电刺激比小脑皮层更敏感,更容易形成病理性通道,而颞叶与额叶之间对刺激的易感性大致相同;(2)病理改变可累及海马,颞叶刺激灶对海马损害最严重,额叶次之,小脑刺激灶对海马影响最小。

Objective To measure the electroconvulsive threshold in different parts of rat cerebral cortex and observe the pathophysiological changes after the convulsive threshold is stable. Methods Healthy female SD rats weighing 180-220 g were randomly divided into a study group and a control group. Electrodes were placed in the frontal lobe, temporal lobe, and cerebellar cortex of all rats. Direct current stimulation was applied twice daily in the study group, but not in the control group. After stable convulsive threshold was achieved in the study group, the SNK-q test was used to compare the convulsive threshold in different subgroups. The rats were then sacrificed to observe the changes of hippocampal neuron damage by Nissl＇s staining. The number of neurons in the hippocampus of rats in each group was counted and then compared using the SNK-q test. Results At the first and second days, the convulsive threshold in the three stimulation subgroups was high, which was ～1100 μA in the frontal lobe, ～1200 μA in the temporal lobe, and ～2100 μA in the cerebellar cortex. With the increase in the duration of stimulation, the threshold of the three groups continued to decrease, eventually reaching a stable level. The mean stable threshold was（511.00±10.97） μA in the frontal lobe,（440±12.46） μA in the temporal lobe, and（1300±53.63） μA in the cerebellar cortex. Although the mean stable threshold did not differ significantly between the frontal lobe and temporal lobe（P〈0.05）, there was a significant difference between the cerebellum and frontal lobe and between the cerebellum and temporal lobe（P〈0.05）. With the extension of stimulation time, compared with the control group, hippocampal CA3 area in rats of the study group exhibited varying degrees of changes, such as disordered neuron arrangement and neuron loss. The average number of neurons was 36 in the control group, 22 in the frontal lobe subgroup, 17 in the temporal lobe subgroup, and 26 in the cerebellum subgroup. Compared with the control group, the number of neurons in the study group decreased significantly（P〈0.05）. There was also a significant difference in the neuron number among the three subgroups（P〈0.05）. The symptoms of rats after electrical stimulation in the cerebellar cortex subgroup were different from those in the frontal and temporal lobe subgroups. The frontal and temporal lobe groups showed typical epileptiform convulsion, such as nodding, limb convulsion, and tonic-clonic seizures; however, the cerebellum group was characterized by systemic tetanic convulsion of limbs and trunk, running, and jumping. Conclusions At the same intensity of electrical stimulation, the temporal lobe and frontal lobe are more sensitive than cerebellar cortex and are easier to develop pathological changes, and the susceptibility to electrical stimulation is comparable between the temporal lobe and frontal lobe. Electrical stimulation can cause pathological changes in the hippocampus, and the hippocampal damage in the temporal lobe subgroup is the most serious. Cerebellar cortex stimulation has the minimum effect on the hippocampus.