Carbone E, Lux H D
Nature. 1984;310(5977):501-2. doi: 10.1038/310501a0.
Calcium channels in excitable membranes are essential for many cellular functions. Recent analyses of the burst-firing mode of some vertebrate neurones suggest that changes in their functional state are controlled by a Ca conductance that is largely inactivated at resting membrane potentials (-50 to -60 mV), but becomes activated following a conditioning hyperpolarization of the cell membrane. Here, using chick and rat sensory neurones, we present evidence for a new type of Ca channel with time- and voltage-dependent properties which is probably responsible for the inactivation behaviour of the Ca conductance. At membrane potentials between -50 and +10 mV, openings of this channel last 3-6 ms and tend to occur in rapid succession. Inactivation of this channel is indicated by prolonged and eventually complete closures brought about by long-lasting depolarizing voltage steps. This channel coexists in isolated membrane patches with the more common Ca channel which is less sensitive to changes in holding potential and shows a considerably shorter average life time and smaller currents.
可兴奋膜中的钙通道对许多细胞功能至关重要。最近对一些脊椎动物神经元爆发式放电模式的分析表明，其功能状态的变化受一种钙电导控制，该电导在静息膜电位（-50至-60 mV）时基本失活，但在细胞膜进行预处理性超极化后被激活。在此，我们利用鸡和大鼠的感觉神经元，提供了一种新型钙通道的证据，该通道具有时间和电压依赖性特性，可能是钙电导失活行为的原因。在膜电位为-50至+10 mV之间时，该通道的开放持续3至6毫秒，并倾向于快速连续发生。通过长时间的去极化电压阶跃导致的延长且最终完全关闭表明该通道失活。在分离的膜片中，这种通道与更常见的钙通道共存，后者对钳制电位变化的敏感性较低，平均寿命明显较短且电流较小。
