Department of Pharmaceutical Toxicology, School of Pharmaceutical Science, China Medical University, Shenyang 110001, China.
Neurochem Int. 2013 Feb;62(3):287-95. doi: 10.1016/j.neuint.2013.01.005. Epub 2013 Jan 16.
Voltage-gated sodium channels (VGSC) have been linked to inherited forms of epilepsy. The expression and biophysical properties of VGSC in the hippocampal neuronal culture model have not been clarified. In order to evaluate mechanisms of epileptogenesis that are related to VGSC, we examined the expression and function of VGSC in the hippocampal neuronal culture model in vitro and spontaneously epileptic rats (SER) in vivo. Our data showed that the peak amplitude of transient, rapidly-inactivating Na(+) current (I(Na,T)) in model neurons was significantly increased compared with control neurons, and the activation curve was shifted to the negative potentials in model neurons in whole cell recording by patch-clamp. In addition, channel activity of persistent, non-inactivating Na(+) current (I(Na,P)) was obviously increased in the hippocampal neuronal culture model as judged by single-channel patch-clamp recording. Furthermore, VGSC subtypes Na(V)1.1, Na(V)1.2 and Na(V)1.3 were up-regulated at the protein expression level in model neurons and SER as assessed by Western blotting. Four subtypes of VGSC proteins in SER were clearly present throughout the hippocampus, including CA1, CA3 and dentate gyrus regions, and neurons expressing VGSC immunoreactivity were also detected in hippocampal neuronal culture model by immunofluorescence. These findings suggested that the up-regulation of voltage-gated sodium channels subtypes in neurons coincided with an increased sodium current in the hippocampal neuronal culture model, providing a possible explanation for the observed seizure discharge and enhanced excitability in epilepsy.
电压门控钠离子通道（VGSC）与遗传性癫痫有关。在海马神经元培养模型中，VGSC 的表达和生物物理特性尚未得到阐明。为了评估与 VGSC 相关的癫痫发生机制，我们在体外海马神经元培养模型和体内自发性癫痫大鼠（SER）中研究了 VGSC 的表达和功能。我们的数据表明，模型神经元中瞬时、快速失活的钠离子电流（I(Na,T)）的峰值幅度明显高于对照神经元，并且在全细胞膜片钳记录中，模型神经元中的激活曲线向负电位偏移。此外，通过单通道膜片钳记录判断，海马神经元培养模型中持续、非失活的钠离子电流（I(Na,P)）的通道活性明显增加。此外，通过 Western blot 评估，在模型神经元和 SER 中，VGSC 亚型 Na(V)1.1、Na(V)1.2 和 Na(V)1.3 的蛋白表达水平上调。在 SER 中，四种 VGSC 蛋白亚型在整个海马体中均存在，包括 CA1、CA3 和齿状回区域，并且通过免疫荧光也在海马神经元培养模型中检测到表达 VGSC 免疫反应性的神经元。这些发现表明，神经元中电压门控钠离子通道亚型的上调与海马神经元培养模型中钠离子电流的增加相一致，为观察到的癫痫发作放电和癫痫时兴奋性增强提供了可能的解释。
