Galvan M, Sedlmeir C
J Physiol. 1984 Nov;356:115-33. doi: 10.1113/jphysiol.1984.sp015456.
Outward membrane currents were studied in neurones of the isolated rat superior cervical ganglion by using a two-micro-electrode or single-micro-electrode voltage-clamp technique. Under current clamp, depolarization elicited electrotonic potentials that displayed marked outward rectification. From negative resting potentials (-70 mV) a short latency, short duration outward rectification was observed. From more positive potentials (-40 mV) a longer latency persistent outward rectification could be demonstrated. Under voltage clamp, four distinct outward currents were observed: a delayed rectifier (IK); a transient outward current (IA); a Ca2+-activated current (IC) and the M-current (IM). The maximum amplitude of IK, IA and IC was 1-2 orders of magnitude greater than IM. Depolarizing from -40 mV to potentials more positive than -20 mV co-activated IK and IC, producing a characteristic N-shaped current voltage curve with a minimum at about +80 mV. Superfusion with Mn2+-containing solutions reduced outward current at all voltages and abolished the N-characteristic; the remaining current (IK) slowly inactivated (tau greater than 1 s). Raising [K+]o from 6 to 36 mmol/l reversed outward tail currents observed in normal solution. Addition of tetraethylammonium ions (1-3 mmol/l) strongly reduced the amplitude of IK and IC. IA was characterized by very rapid activation at potentials more positive than -60 mV and by fast and complete inactivation at potentials in the activation range. The amplitude of IA was dependent on [K+]o and was reduced by external 4-aminopyridine (1-3 mmol/l). The activation appeared to depend on the nature and concentration of divalent cations present in the superfusate. It is concluded that the soma membrane of rat sympathetic neurones, like many other vertebrate and invertebrate neurones, contains multiple populations of K+ channels. The possible functions of these in the control of ganglion cell excitability are discussed.
采用双微电极或单微电极电压钳技术，对离体大鼠颈上神经节神经元的外向膜电流进行了研究。在电流钳制下，去极化引发电紧张电位，该电位表现出明显的外向整流。从负的静息电位（-70mV）开始，观察到潜伏期短、持续时间短的外向整流。从更正的电位（-40mV）开始，可以证明存在潜伏期更长的持续性外向整流。在电压钳制下，观察到四种不同的外向电流：延迟整流钾电流（IK）；瞬时外向电流（IA）；钙激活电流（IC）和M电流（IM）。IK、IA和IC的最大幅值比IM大1 - 2个数量级。从-40mV去极化到比-20mV更正的电位会共同激活IK和IC，产生特征性的N形电流-电压曲线，在约+80mV处有最小值。用含Mn2 +的溶液灌流会降低所有电压下的外向电流，并消除N特征；剩余电流（IK）缓慢失活（时间常数大于1s）。将细胞外钾离子浓度（[K + ]o）从6mmol/L提高到36mmol/L可使正常溶液中观察到的外向尾电流反转。加入四乙铵离子（1 - 3mmol/L）会强烈降低IK和IC的幅值。IA的特点是在比-60mV更正的电位下非常快速激活，在激活范围内的电位下快速且完全失活。IA的幅值取决于[K + ]o，并会被细胞外4 - 氨基吡啶（1 - 3mmol/L）降低。激活似乎取决于灌流液中存在的二价阳离子的性质和浓度。结论是，大鼠交感神经元的胞体膜与许多其他脊椎动物和无脊椎动物神经元一样，含有多种钾通道群体。讨论了这些通道在控制神经节细胞兴奋性方面可能的功能。
