KINETICS AND SELECTIVITY OF A LOW-VOLTAGE-ACTIVATED CALCIUM CURRENT IN CHICK AND RAT SENSORY NEURONS
KINETICS AND SELECTIVITY OF A LOW-VOLTAGE-ACTIVATED CALCIUM CURRENT IN CHICK AND RAT SENSORY NEURONS
复制标题
DOI：
10.1113/jphysiol.1987.sp016551
复制
发表时间：
1987-05-01
影响因子：
5.5
通讯作者：
LUX, HD
中科院分区：
文献类型：
--
作者：
CARBONE, E;LUX, HD
1. 利用膜片钳技术的全细胞记录模式，我们研究了低压激活（l.va.a）的动力学和选择性特性。鸡和大鼠背根神经节（d.r.g）神经元Ca2+电流。2. l - v - a电流在-50 mV左右激活，最大振幅在-30 ~ -20 mV之间，鸡细胞平均为-0.16 nA，大鼠细胞平均为-0.3 nA，细胞外Ca2+为5 mm。在-60和-20 mV之间，该电流的峰值时间tp随着膜去极化的增加而减少。在22度的温度下，tp的e倍变化需要雏鸡的电位变化14 mV，大鼠d.r.g.g细胞的电位变化17 mV。c . 3。在-50和+20 mV之间，该电流的失活速度很快，单指数和电压相关。与鸡相比，大鼠的失活时间常数Th更小，对电压的依赖性更小。4. 当细胞外Ca2+浓度从1到95 mM变化时，这些电流的振幅增加了5-10倍。电流的振幅和动力学参数沿电压轴表现出典型的位移。Ca2+电流振幅与激活-失活动力学之间没有相关性，这表明控制这些过程的反应速率不依赖于Ca2+的进入。5. 失活后的恢复与电压有关，并以1秒左右的时间常数tr进行。通过将电势从-80 mV改为-120 mV， Tr几乎减半。与膜复极化相关的尾电流也与电压相关，呈指数增长。当电势从-60毫伏变为-100毫伏时，它们的时间常数减小了1 / 3。第二个和更突出的Ca2+电流在电位正至-20 mV（高压激活的Ca2+电流，h.v.a.）时被激活，掩盖了l.v.a.电流的时间过程。在-20和0 mV之间，整个电流达到峰值的时间增加了2倍，但在更高的膜电位下再次减少。在这个电位范围内，失活速度也明显变慢。8. 使用高细胞内Ca2+浓度，[Ca2+]1或内部氟化物盐，可以显著降低hva组分对总膜电流的贡献。这使得在更宽的电位范围（-50至+30 mV）内更精确地研究l.v.a电流的动力学参数和I-V特性成为可能。9. 5 mM-Ni2+或100 μ m - cd2 +可逆阻断低压和高压电流。用Ba2+代替Ca2+使低压电流降低了约五分之一，但使高压电流的振幅大约增加了一倍。另一方面，Sr2+使l.v.a.和h.v.a.分量的振幅增加了五分之一。通过该通道的Mg2+电流无法分辨。
1. Using the whole-cell recording mode of the patch-clamp technique, we have investigated kinetic and selectivity properties of a low-voltage-activated (l.v.a.) Ca2+ current in chick and rat dorsal root ganglion (d.r.g.) neurones. 2. L.v.a currents were activated at about -50 mV and reached maximum amplitudes between -30 and -20 mV with averages of -0.16 nA in chick and -0.3 nA in rat d.r.g. cells with 5 mM-extracellular Ca2+. Between -60 and -20 mV, the time to peak, tp, of this current decreased with increasing membrane depolarizations. An e-fold change of tp required a 14 mV potential change in chick and a 17 mV change in rat d.r.g. cells at 22.degree. C. 3. Between -50 and +20 mV inactivaiton of this current was fast, single exponential and voltage dependent. In rat, the time constant of inactivation, Th, was smaller and less voltage dependent than in chick. 4. The amplitude of these currents increased by a factor of 5-10, when the extracellular Ca2+ concentration was changed from 1 to 95 mM. Amplitudes and kinetic parameters of the currents showed typical shifts along the voltage axis. No correlation between Ca2+ current amplitudes and activation-inactivation kinetics was found, suggesting that the reaction rates which control these processes are not dependent on Ca2+ entry. 5. Recovery from inactivation was voltage dependent and developed with a time constant, tr, in the order of 1 s. Tr was nearly halved by changing the potential from -80 to -120 mV. 6. Tail currents associated with membrane repolarization were also voltage dependent and developed exponentially. Their time constant decreased by a factor of 3 when the potential was changed from -60 to -100 mV. 7. A second and more prominent Ca2+ current was activated at potentials positive to -20 mV (high-voltage-activated Ca2+ currents, h.v.a.), masking the time course of l.v.a. currents. Between -20 and 0 mV, time to peak of the entire current increased by a factor of 2 but decreased again at higher membrane potentials. Inactivation also became significantly slower in this potential range. 8. The contribution of the h.v.a. component to the total membrane current was markedly reduced using a high intracellular Ca2+ concentration, [Ca2+]1, or internal fluoride salts. This made it possible to study the kinetic parameters and the I-V characteristics of the l.v.a. current more precisely over a wider potential range (-50 to +30 mV). 9. L.v.a. and h.v.a. currents were blocked reversibly by 5 mM-Ni2+ or 100 .mu.M-Cd2+. Replacement of Ca2+ with Ba2+ reduced the l.v.a. currents by about one-fifth, but roughly doubled the amplitude of h.v.a. currents. Sr2+, on the other hand, increased the amplitude of both l.v.a. and h.v.a. components by one-fifth. Mg2+ currents through this channel could not be resolved.