Ogata N, Tatebayashi H
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Pflugers Arch. 1990 Jul;416(5):594-603. doi: 10.1007/BF00382695.
Neurones of the neostriatum were freshly dispersed from the adult guinea pig brain. A fast, transient inward Na+ current (INa) was analysed using the whole-cell patch-clamp technique. Upon depolarizations, INa developed with a sigmoidal time course, which was described by m3 kinetics. INa showed an activation threshold of about -60 mV, a peak current at -30 to -20 mV, and a reversal of polarity at +60 mV. The steady-state activation (m infinity) curve for INa had a slope factor of about 9 mV for a change in the rate constant by a factor of e) in the range between -50 mV and -20 mV. Conversely, the backward rate constant (beta m) decreased as the membrane was depolarized (about 31 mV for an e-fold change). The steady-state inactivation (h infinity) curve was well expressed by the Boltzmann's equation with a half-inactivation potential of -62 mV and a slope parameter of 6 mV. The time course of INa decay followed a second-order process, whereas the recovery from inactivation was described as a first-order process. The tau h curve showed a bell-shaped configuration with a maximum value at -60 mV. The forward rate constants (alpha h) decreased as the membrane was depolarized (about 17 mV for an e-fold change) in the range between -50 mV and -20 mV. The backward rate constants (beta h) increased as the membrane was depolarized (about 10 mV for an e-fold change). There was a significant overlap between m infinity and h infinity curves, suggesting a steady influx of Na+ (window current).
新纹状体神经元取自成年豚鼠大脑并进行新鲜分离。使用全细胞膜片钳技术分析快速、瞬态内向Na⁺电流（INa）。去极化时，INa呈S形时间进程发展，由m³动力学描述。INa的激活阈值约为 -60 mV，在 -30至 -20 mV时出现峰值电流，在 +60 mV时极性反转。INa的稳态激活（m无穷大）曲线在 -50 mV至 -20 mV范围内，速率常数变化一个e倍因子时，斜率因子约为9 mV。相反，反向速率常数（βm）随膜去极化而降低（e倍变化约为31 mV）。稳态失活（h无穷大）曲线用玻尔兹曼方程很好地描述，半失活电位为 -62 mV，斜率参数为6 mV。INa衰减的时间进程遵循二级过程，而失活恢复描述为一级过程。τh曲线呈钟形，在 -60 mV时具有最大值。正向速率常数（αh）在 -50 mV至 -20 mV范围内随膜去极化而降低（e倍变化约为17 mV）。反向速率常数（βh）随膜去极化而增加（e倍变化约为10 mV）。m无穷大与h无穷大曲线之间存在显著重叠，表明存在稳定的Na⁺内流（窗电流）。
