电压对终板电流时间进程的影响。

The effect of voltage on the time course of end-plate currents.

Magleby K L, Stevens C F

J Physiol. 1972 May;223(1):151-71. doi: 10.1113/jphysiol.1972.sp009839.

Abstract

End-plate currents have been studied in glycerol-treated frog sartorius nerve-muscle preparations with the voltage clamp technique.2. End-plate currents follow a simple exponential time course over most of their declining phase.3. The rate constant alpha that characterizes this exponential decay depends upon membrane potential V according to the relationship alpha (V) = Be(AV), with A = 0.00795 +/- 0.00043 (S.E.) mV(-1) and B = 1.67 +/- 0.04 (S.E.) msec(-1).4. Voltage sensitivity decreases (that is, A in the above equation becomes smaller) as the recording and current-passing electrodes are moved away from the end-plate region.5. The voltage sensitivity of alpha is decreased by decreasing the gain of the voltage clamp amplifier.6. Changing the end-plate current amplitude by curare treatment, by increased calcium ion concentration, and by facilitation and depression has essentially no effect on end-plate current time course.7. When membrane potential is changed step-wise during the decaying phase of the end-plate conductance change, currents begin to decline with a rate constant alpha appropriate to the new membrane potential in less than 0.2 msec.8. Treatment with prostigmine methylsulphate in concentrations up to 50 mug/ml. slows end-plate current decay but has little effect on voltage sensitivity. That is, B in the above equation is decreased by prostigmine treatment, but A is relatively unaffected.

摘要

运用电压钳技术，对甘油处理过的青蛙缝匠肌神经 - 肌肉标本中的终板电流进行了研究。
终板电流在其下降阶段的大部分时间内遵循简单的指数时间进程。
表征这种指数衰减的速率常数α取决于膜电位V，其关系为α(V)=Be(AV)，其中A = 0.00795±0.00043（标准误）mV⁻¹，B = 1.67±0.04（标准误）msec⁻¹。
随着记录电极和通电流电极远离终板区域，电压敏感性降低（即上述方程中的A变小）。
通过降低电压钳放大器的增益，α的电压敏感性降低。
用箭毒处理、增加钙离子浓度以及通过易化和抑制改变终板电流幅度，对终板电流的时间进程基本没有影响。
当在终板电导变化的衰减阶段逐步改变膜电位时，电流在不到0.2毫秒内开始以与新膜电位相应的速率常数α下降。
用浓度高达50微克/毫升的甲基硫酸新斯的明处理会减缓终板电流衰减，但对电压敏感性影响很小。也就是说，上述方程中的B因新斯的明处理而降低，但A相对不受影响。