Gating currents and charge movements in excitable membranes.
Gating currents and charge movements in excitable membranes.
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DOI：
10.1007/bfb0030498
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发表时间：
1978-01-01
期刊：
影响因子：
--
通讯作者：
Almers, W
中科院分区：
文献类型：
--
作者：
Almers, W
许多细胞利用细胞膜电位调节其生理功能。其中比较著名的例子有：(1)调节神经和肌肉膜的钠和钾的渗透性，(2)调节突触前末端的递质释放，(3)调节肌肉细胞内钙离子的浓度和收缩，可能还有(4)调节肾上腺髓质细胞分泌肾上腺素，(5)调节胰腺细胞分泌胰岛素。随着越来越多不同的细胞类型产生电生理分析，我们无疑会发现细胞膜电位调节的其他实例。电位变化和生理反应之间的事件序列可能是复杂的，但人们期望它总是从电压传感器细胞膜的运动、重新定向或结构变化开始，电压传感器是一种分子，它可以对细胞膜电位做出反应，因为它或它的一部分具有大的偶极矩。在膜电位变化的影响下，这种电压传感器在膜内运动或扭转，产生电流，即位移电流，在有利条件下可以记录。在蛙类骨骼肌、各种神经纤维（乌贼的轴突、蛙的髓鞘神经和蚯蚓的巨轴突）和一些蜗牛神经细胞体的电压钳实验中，记录到了可能由电压传感器运动引起的位移电流。肌肉中的位移电流被认为是由用于兴奋-收缩耦合的电压传感器产生的。在各种神经纤维中观察到的这些可能代表了伴随钠膜渗透性变化的结构重排，通常被称为“门控电流”；蜗牛神经元中的这些可能与细胞膜对钙的通透性调节有关。所有这些观察结果都被认为以某种形式与离子通道的打开和关闭（门控）有关，离子通道是膜上的小离子渗透孔。研究得最透彻的离子通道是钠离子和钾离子
Many cells use the cell membrane potential to regulate their physiologic functions. Among the better known examples are:(1) regulation of sodium and potassium permeabilities in nerve and muscle membranes,(2) regulation of transmitter release by the presynaptic terminal and (3) of intracellular Ca 2÷ concentration and contraction in muscle, and, possibly,(4) the regulation of adrenalin secretion by adrenal medulla cells and (5) of insulin secretion by pancreatic cells. As more and more different cell types yield to electrophysiologic analysis, we will no doubt find other instances of regulation by the cell membrane potential. The sequence of events between potential change and physiologic response may be complicated, but one expects that it will always begin with the movement, reorientation, or structural change in the cell membrane of a voltage sensor, a molecule which can respond to the cell membrane potential because it or parts of it have a large dipole moment. While moving or twisting inside the membrane under the influence of a change in membrane potential, such a voltage sensor produces an electric current, a displacement current, which can be recorded under favorable conditions. Displacement currents probably caused by movement of voltage sensors have been recorded in voltageclamp experiments on frog skeletal muscle, various nerve fibers (squid axons, frog myelinated nerve, and giant axons from the earthworm Myxicola) and some snail nerve cell bodies. The displacement currents in muscle are thought to result from the voltage-sensor for excitation-contraction coupling. Those observed in the various nerve fibers probably represent the structural rearrangements accompanying membrane permeability changes to sodium and are often called" gating currents"; those in snail neurons may be associated with the regulation of the cell membrane permeability to calcium. All of these observations are thought to be related in some form or another to the opening and closing (gating) of ionic channels, small ion-permeable holes in the membrane. Among the most thoroughly studied ionic channels are the sodium and potassium