慢性癫癎模型海马神经元内钙稳态和钙动力学的长期变化

摘要

目的 探讨海马神经元内长期钙离子([Ca2+]i)和动力学变化在癫疴发生机制中的作用.方法 建立氯化锂-匹罗卡品慢性癫癎模型,于致痫后6 h和1、3、7、14、30 d不同时间点应用激光共聚焦显微镜观察离体海马神经元内[Ca2+]i的变化以及谷氨酸负荷后神经元内[Ca2+]i恢复速度的变化.结果 正常对照组大鼠急性分离海马神经元[Ca2+]i为(95.4±22.1)nmol/L,致癎后急剧升高至(867.6±35.2)nmol/L,第7天降低(292.8±18.3)mnol/L,此后持续在此水平,30 d后降至(220.8±17.6)nmol/L,仍高于对照组(t=12.55,P<0.01);正常对照组大鼠92%的海马神经元内[Ca2+]i处于正常范围内(25～150 nmol/L),致癎后6 h,所有神经元[Ca2+]i均有升高,并且85%的神经元高于500 nmol/L,致癎7、14、30 d后分别有75%、60%、52%的神经元[Ca2+]i高于正常值,但高于500 nmol/L者逐渐减少;经接触5 μmol/L谷氨酸人工脑脊液2 min后,对照组神经元可在(9.5±3.4)min内恢复至基线水平,而急性期、潜伏期、慢性期的癫癎神经元均存在明显延迟(t=5.08、4.56、4.21,P<0.01).结论 氯化锂-匹罗卡品致疴后可造成海马神经元内长期的[Ca2+]i和钙动力学改变,该种长期可塑性改变在慢性癫癎模型的诱发和维持中起着重要作用.%Objective To study the role of calcium homeostatic and kinetics in the epileptogenesis activity. Methods Hippocampal neurons were acutely isolated from controls and status epilepticus (SE) models induced by lithium-pilocarpine at different time point. The [Ca2+]i levels were detected by laser scanning confocal microscope. And the ability to restore resting [Ca2+]i levels after a brief exposure to 5 μmol/L glutamate in control and epileptic neurons were evaluated. Results The [Ca2+]i level of acute separated hippocampal neurons in the control rats was (95.4±22. 1) nmol/L After injection of lithium pilocarpine, the [Ca2+]i level in hippecampal neurons increased dramatically to (867.6±35.2) nmol/L, and decreased to (292.8 ± 18.3) nmol/L on the 7th day, lasting for about 30 days ((220. 8± 17.6) nmol/L), it is higher than that in the control group (t = 12. 55, P < 0.01). The distribution of neuronal [Ca22+]i showed that 92% of control neurons were in the normal range of [Ca2+]i level (25-150 nmol/L) ; After 6 hours, however [Ca2+]i levels of all SE neurons increased, and 85% of which were higher than 500 nmol/L; After 7, 14 and 30 days, there were 75%, 60% and 52% of SE neurons still manifested an elevated [Ca22+]i level, but less than 500 nmol/L. After the exposure to 5 μmol/L glutamate treatment for 2 minutes, [Ca2+]i of the control neurons restored to baseline values in (9. 5±3.4) minutes, whereas the SE rats of acute, latent and chronic phases did not (t = 5.08, 4. 56, 4. 21, all P < 0. 01). Conclusion Lithium-pilocarpine induced epilepsy causes a long-term alteration of calcium homeostatic mechanisms of hippocampus neurons, which may play an important role in the development and maintenance of spontaneous recurrent seizures.