CALCIUM CURRENT ACTIVATION KINETICS IN NEURONS OF THE SNAIL LYMNAEA-STAGNALIS
CALCIUM CURRENT ACTIVATION KINETICS IN NEURONS OF THE SNAIL LYMNAEA-STAGNALIS
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DOI：
10.1113/jphysiol.1984.sp015105
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发表时间：
1984-01-01
影响因子：
5.5
通讯作者：
STIMERS, JR
中科院分区：
文献类型：
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作者：
BYERLY, L;CHASE, PB;STIMERS, JR
Lymna的激活动力学和钙电流的大小都强烈地依赖于温度。活化时间常数的倒数Q10为4.9±-。0.2，最大电流的Q10为2.3+-。0.1。通过将温度降低到7-10度。C，解决了钙尾流。Cd~(2+)阻断Ca~(2+)电流具有电压依赖性，且在较高的正电位下更为有效。根据尾电流的大小确定，直到膜电位大于+70 mV时，钙通透性才被最大限度地激活。钙通透性在30-35 mV范围内呈半激活状态。钙电流的开沟电流-电压关系与恒定电场方程的预测大体一致。当电位降至-60 mV时，在负电位下没有电流饱和迹象。钙尾流的衰减至少有2个时间常数，一个为200-400微秒，另一个为2-4ms。尽管这些时间常数与电压没有很强的相关性，但在-60 mV时，尾流的快分量与慢分量的幅度之比比在0 mV时要大得多。Ba尾电流的时间过程与Ca尾流的时间过程非常相似。钙电流激活的时间过程遵循m~2动力学，在-50 mV到-110 mV之间的保持电位没有表现出Cole-Moore类型的漂移。在第一个正脉冲之后1毫秒施加的第二个正脉冲期间，钙电流被更快地激活，而没有单个正脉冲的钙电流的延迟特性。钙电流的激活可用线性时序模型表示。描述钙电流接通和关断的最简单模型必须至少有3个闭合状态，然后是一个开路状态。
Both the activation kinetics and the magnitude of the Ca current in Lymnaea are strongly dependent on temperature. The Q10 for the reciprocal of the activation time constant is 4.9 .+-. 0.2 and the Q10 for the maximum current is 2.3 .+-. 0.1. By lowering the temperature to 7-10.degree. C, the Ca tail currents were resolved. The block of Ca current by Cd2+ is voltage dependent, being more effectiveat more positive potentials. As determined from the magnitude of the tail currents, the Ca permeability is not maximally activated until the membrane potential is greater than +70 mV. The Ca permeability is half activated in the range 30-35 mV. The open-channel current-voltage relation for the Ca current is in rough agreement with the prediction of the constant-field equation. There is no indication of current saturation at negative potentials for potentials down to -60 mV. The Ca tail current decays with at least 2 time constants, one 200-400 .mu.s and the other 2-4 ms. Although these time constants are not strongly voltage dependent, the ratio of the amplitude of the fast component of the tail current to that of the slow component is much larger at -60 mV than at 0 mV. The time course of the Ba tail current is very similar to that of the Ca tail current. The time course of the activation of the Ca current follows m2 kinetics and does not show evidence for a Cole-Moore-type shift for holding potentials between -50 and -110 mV. During a 2nd positive pulse applied 1 ms after the 1st, the Ca current activates more rapidly, without the delay characteristic of the Ca current of a single positive pulse. The activation of the Ca current can be represented by a linear sequential model. The simplest model that describes both the turn-on and the turn-off of the Ca current must have at least 3 closed states, followed by a single open state.