Keja J A, Stoof J C, Kits K S
Department of Neurology, Free University, Amsterdam, The Netherlands.
Neuroendocrinology. 1991 Apr;53(4):349-59. doi: 10.1159/000125741.
Voltage-gated currents through Ca channels in rat melanotrophs in short-term primary culture were investigated in whole cell voltage clamp recordings, using Ba2+ ions as charge carrier. At potentials higher than -50 mV a transient current (It) was activated, which inactivated entirely during a 150-ms command pulse and reached a maximal amplitude at -10 mV. At potentials higher than -20 mV a second component (Is) appeared, which inactivated slowly and had its maximal amplitude between 0 and +10 mV. The relative amplitudes of It and Is differed between cells. Application of 40 microM NiCl2 reversibly blocked It while leaving Is intact, whereas 20 microM CdCl2 reversibly blocked Is, but not It. Nifedipine blocked Is concentration dependently, but did not affect It. The steady state inactivation of It occurred between -80 and -40 mV. The steady-state inactivation curve of Is was located between -60 and 0 mV. The latter inactivation curve showed two phases, which were fitted best by the sum of two Boltzmann equations, suggesting the existence of two populations of Is channels.
在短期原代培养的大鼠黑素细胞中，使用Ba2+离子作为电荷载体，通过全细胞电压钳记录研究了钙通道的电压门控电流。在高于-50 mV的电位下，激活了一个瞬态电流（It），该电流在150 ms的指令脉冲期间完全失活，并在-10 mV时达到最大幅度。在高于-20 mV的电位下，出现了第二个成分（Is），其失活缓慢，最大幅度在0至+10 mV之间。不同细胞中It和Is的相对幅度有所不同。施加40μM NiCl2可可逆地阻断It，而Is不受影响，而20μM CdCl2可可逆地阻断Is，但不影响It。硝苯地平浓度依赖性地阻断Is，但不影响It。It的稳态失活发生在-80至-40 mV之间。Is的稳态失活曲线位于-60至0 mV之间。后一条失活曲线显示出两个阶段，用两个玻尔兹曼方程的和拟合效果最佳，表明存在两种类型的Is通道。
