Sah P, Gibb A J, Gage P W
Department of Physiology, John Curtin School of Medical Research, Australian National University, Canberra.
J Gen Physiol. 1988 Aug;92(2):263-78. doi: 10.1085/jgp.92.2.263.
Currents were generated by depolarizing pulses in voltage-clamped, dissociated neurons from the CA1 region of adult guinea pig hippocampus in solutions containing 1 microm tetrodotoxin. When the extracellular potassium concentration was 100 mM, the currents reversed at -8.1 +/- 1.6 mV (n = 5), close to the calculated potassium equilibrium potential of -7 mV. The currents were depressed by 30 mM tetraethylammonium in the extracellular solution but were unaffected by 4-aminopyridine at concentrations of 0.5 or 1 mM. It was concluded that the currents were depolarization-activated potassium currents. Instantaneous current-voltage curves were nonlinear but could be fitted by a Goldman-Hodgkin-Katz equation with PNa/PK = 0.04. Conductance-voltage curves could be described by a Boltzmann-type equation: the average maximum conductance was 65.2 +/- 15.7 nS (n = 9) and the potential at which gK was half-maximal was -4.8 +/- 3.9 mV (mean +/- 1 SEM, n = 10). The relationship between the null potential and the extracellular potassium concentration was nonlinear and could be fitted by a Goldman-Hodgkin-Katz equation with PNa/PK = 0.04. The rising phase of potassium currents and the decay of tail currents could be fitted with exponentials with single time constants that varied with membrane potential. Potassium currents inactivated to a steady level with a time constant of approximately 450 ms that did not vary with potential. The currents were depressed by substituting cobalt or cadmium for extracellular calcium but similar effects were not obtained by substituting magnesium for calcium.
在含有1微摩尔河豚毒素的溶液中，对成年豚鼠海马CA1区电压钳制的解离神经元施加去极化脉冲来产生电流。当细胞外钾浓度为100 mM时，电流在-8.1±1.6 mV处反转（n = 5），接近计算得出的-7 mV钾平衡电位。细胞外溶液中的30 mM四乙铵可抑制这些电流，但0.5或1 mM浓度的4-氨基吡啶对其无影响。得出的结论是，这些电流是去极化激活的钾电流。瞬时电流-电压曲线是非线性的，但可用Goldman-Hodgkin-Katz方程拟合，其中PNa/PK = 0.04。电导-电压曲线可用玻尔兹曼型方程描述：平均最大电导为65.2±15.7 nS（n = 9），gK为最大值一半时的电位为-4.8±3.9 mV（平均值±1标准误，n = 10）。零电位与细胞外钾浓度之间的关系是非线性的，可用Goldman-Hodgkin-Katz方程拟合，其中PNa/PK = 0.04。钾电流的上升相和尾电流的衰减可用随膜电位变化的单时间常数指数函数拟合。钾电流以约450 ms的时间常数失活至稳定水平，该时间常数不随电位变化。用钴或镉替代细胞外钙可抑制这些电流，但用镁替代钙未获得类似效果。
