Wisgirda M E, Dryer S E
Department of Biological Science B-221, Florida State University, Tallahassee 32306.
Pflugers Arch. 1993 Jun;423(5-6):418-26. doi: 10.1007/BF00374936.
A-currents were studied in acutely dissociated chick autonomic neurons. Switching from salines containing 4 mM Mg2+ to salines containing 4 mM Ca2+ caused a large positive shift in the voltage dependence of steady-state inactivation, but had no effect on the voltage dependence or kinetics of activation, deactivation, the rate at which channels became inactivated, or the rate at which channels recovered from inactivation. This effect saturated with increasing concentrations of Ca2+. Other group IIA divalent cations were less effective than Ca2+, in the order Ca2+ > Ba2+ > Mg2+ = Sr2+. Application of 4 mM Mg2+ partially antagonized the effects of 4 mM Ca2+. The results suggest that divalent cations selectively alter the voltage dependence of steady-state inactivation by acting at sites accessible from the outside of the cell.
对急性分离的鸡自主神经元中的A电流进行了研究。从含有4 mM Mg2+的盐溶液切换到含有4 mM Ca2+的盐溶液，导致稳态失活的电压依赖性出现大幅正向偏移，但对激活、失活的电压依赖性或动力学、通道失活的速率或通道从失活中恢复的速率没有影响。这种效应随着Ca2+浓度的增加而饱和。其他IIA族二价阳离子的效果不如Ca2+，顺序为Ca2+ > Ba2+ > Mg2+ = Sr2+。施加4 mM Mg2+可部分拮抗4 mM Ca2+的作用。结果表明，二价阳离子通过作用于细胞外可及的位点，选择性地改变稳态失活的电压依赖性。
