Wang Jun, Ou Shao-Wu, Bai Yun-Fei, Wang Yun-Jie, Xu Zhi-Qing David, Luan Guo-Ming
Department of Neurosurgery, Beijing Sanbo Brain Hospital of Capital Medical University, Beijing 100093, P.R. China.
Department of Neurosurgery, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China.
Mol Med Rep. 2017 Jul;16(1):719-729. doi: 10.3892/mmr.2017.6654. Epub 2017 May 30.
It has previously been demonstrated that there are various voltage gated sodium channel (Nav) 1.5 splice variants expressed in brain tissue. A total of nine Nav1.5 isoforms have been identified, however, the potential presence of further Nav1.5 variants expressed in brain neurons remains to be elucidated. The present study systematically investigated the expression of various Nav1.5 splice variants and their associated electrophysiological properties in the rat brain tissue, via biochemical analyses and whole‑cell patch clamp recording. The results demonstrated that adult Nav1.5 was expressed in the rat, in addition to the neonatal Nav1.5, Nav1.5a and Nav1.5f isoforms. Further studies indicated that the expression level ratio of neonatal Nav1.5 compared with adult Nav1.5 decreased from 1:1 to 1:3 with age development from postnatal (P) day 0 to 90. This differed from the ratios observed in the developing rat hearts, in which the expression level ratio decreased from 1:4 to 1:19 from P0 to 90. The immunohistochemistry results revealed that Nav1.5 immunoreactivity was predominantly observed in neuronal cell bodies and processes, whereas decreased immunoreactivity was detected in the glial components. Electrophysiological analysis of Nav1.5 in the rat brain slices revealed that an Na current was detected in the presence of 300 nM tetrodotoxin (TTX), however this was inhibited by ~1 µM TTX. The TTX‑resistant Na current was activated at ‑40 mV and reached the maximum amplitude at 0 mV. The results of the present study demonstrated that neonatal and adult Nav1.5 were expressed in the rat brain and electrophysiological analysis further confirmed the functional expression of Nav1.5 in brain neurons.
先前已经证明，在脑组织中表达有多种电压门控钠通道（Nav）1.5剪接变体。总共已鉴定出9种Nav1.5亚型，然而，在脑神经元中表达的其他Nav1.5变体的潜在存在仍有待阐明。本研究通过生化分析和全细胞膜片钳记录，系统地研究了大鼠脑组织中各种Nav1.5剪接变体的表达及其相关的电生理特性。结果表明，除了新生Nav1.5、Nav1.5a和Nav1.5f亚型外，成年Nav1.5也在大鼠中表达。进一步的研究表明，随着从出生后（P）第0天到90天的年龄发展，新生Nav1.5与成年Nav1.5的表达水平比从1:1降至1:3。这与发育中的大鼠心脏中观察到的比例不同，在发育中的大鼠心脏中，从P0到90，表达水平比从1:4降至1:19。免疫组织化学结果显示，Nav1.5免疫反应性主要在神经元细胞体和突起中观察到，而在神经胶质成分中检测到免疫反应性降低。对大鼠脑切片中Nav1.5的电生理分析表明，在存在300 nM河豚毒素（TTX）的情况下检测到钠电流，然而该电流被约1 μM TTX抑制。耐TTX的钠电流在-40 mV时被激活，并在0 mV时达到最大幅度。本研究结果表明，新生和成年Nav1.5在大鼠脑中表达，电生理分析进一步证实了Nav1.5在脑神经元中的功能性表达。
