Fast-deactivating calcium channels in chick sensory neurons.
Fast-deactivating calcium channels in chick sensory neurons.
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雏鸡感觉神经元中的快速解释钙通道。
DOI：
10.1085/jgp.92.2.197
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发表时间：
1988-08
影响因子：
3.8
通讯作者：
Armstrong, C M
中科院分区：
文献类型：
--
作者：
Swandulla, D;Armstrong, C M
在培养6-10天的鸡背根神经节（DRG）细胞上研究了全细胞Ca和Ba电流。使用改进的膜片钳电路在膜上施加具有15微秒上升时间的电压阶跃。膜电流的变化可以在测试脉冲开始后30微秒测量。在消除Na和K电流的条件下记录通过Ca通道的电流。尾电流，与钙通道关闭，衰减在两个不同的阶段，非常适合的两个指数的总和。在-80 mV、20 ℃下，时间常数τ f和τ s接近160微秒和1.5 ms。尾电流成分，称为FD和SD（快速失活和缓慢失活），是Ca通道电流。当Mg 2+取代浴中的所有其他二价阳离子时，它们大大减少。当测试脉冲持续时间增加到100 ms时，SD组分几乎完全失活。当细胞保持在膜电位正至-50 mV时，SD组分被抑制，并被100-200 μ M Ni 2+阻断。该行为表明SD组分是由于先前在该制备中描述的低压激活（LVA）Ca通道的关闭。FD组件在20 ℃时用10 ms测试脉冲完全激活至+20 mV，在500 ms测试脉冲期间失活至约30%。保持在-40 mV时，其振幅降低，但微摩尔浓度的Ni 2+仅略微降低。用Ba 2+替代Ca 2+使FD尾电流幅度增加约1.5倍。失活动力学没有改变（a）当通道在逐渐变长的脉冲期间失活时或（B）当激活程度变化时。此外，τ f既不受改变保持电位的影响，也不受改变测试脉冲幅度的影响。将温度从20摄氏度降低到10摄氏度，τ f降低了2.5倍。在所有情况下，FD分量通过单个指数非常好地拟合。没有迹象表明存在其他显著尺寸的尾部组件。我们的研究结果表明，FD组件是由于关闭的一类钙通道共存的LVA钙通道类型在鸡DRG神经元。
Whole-cell Ca and Ba currents were studied in chick dorsal root ganglion (DRG) cells kept 6-10 in culture. Voltage steps with a 15- microseconds rise time were imposed on the membrane using an improved patch-clamp circuit. Changes in membrane current could be measured 30 microseconds after the initiation of the test pulse. Currents through Ca channels were recorded under conditions that eliminate Na and K currents. Tail currents, associated with Ca channel closing, decayed in two distinct phases that were very well fitted by the sum of two exponentials. The time constants tau f and tau s were near 160 microseconds and 1.5 ms at -80 mV, 20 degrees C. The tail current components, called FD and SD (fast-deactivating and slowly deactivating), are Ca channel currents. They were greatly reduced when Mg2+ replaced all other divalent cations in the bath. The SD component inactivated almost completely as the test pulse duration was increased to 100 ms. It was suppressed when the cell was held at membrane potentials positive to -50 mV and was blocked by 100-200 microM Ni2+. This behavior indicates that the SD component was due to the closing of the low-voltage-activated (LVA) Ca channels previously described in this preparation. The FD component was fully activated with 10-ms test pulses to +20 mV at 20 degrees C, and inactivated to approximately 30% during 500-ms test pulses. It was reduced in amplitude by holding at - 40 mV, but was only slightly reduced by micromolar concentrations of Ni2+. Replacement of Ca2+ with Ba2+ increased the FD tail current amplitudes by a factor of approximately 1.5. The deactivation kinetics did not change (a) as channels inactivated during progressively longer pulses or (b) when the degree of activation was varied. Further, tau f was affected neither by changing the holding potential nor by varying the test pulse amplitude. Lowering the temperature from 20 to 10 degrees C decreased tau f by a factor of 2.5. In all cases, the FD component was very well fitted by a single exponential. There was no indication of an additional tail component of significant size. Our findings indicate that the FD component is due to closing of a single class of Ca channels that coexist with the LVA Ca channel type in chick DRG neurons.