Moore J W, Hines M, Harris E M
Biophys J. 1984 Oct;46(4):507-14. doi: 10.1016/S0006-3495(84)84048-5.
Extracellular resistance in series (Rs) with excitable membranes can give rise to significant voltage errors that distort the current records in voltage-clamped membranes. Electrical methods for measurement of and compensation for such resistances are described and evaluated. Measurement of Rs by the conventional voltage jump in response to a current step is accurate but the measurement of sine-wave admittance under voltage-clamp conditions is better, having about a fivefold improvement in resolution (+/- 0.1 omega cm2) over the conventional method. Conventional feedback of the membrane current signal to correct the Rs error signal leads to instability of the voltage clamp when approximately two-thirds of the error is corrected. We describe an active electronic bridge circuit that subtracts membrane capacitance from the total membrane current and allows full, yet stable, compensation for the voltage error due to ionic currents. Furthermore, this method provides not only fast and accurate control of the membrane potential in response to a command step, but also fast recovery following an abrupt change in the membrane conductance. Marked changes in the kinetics and amplitude of ionic currents resulting from full compensation for Rs are shown for several typical potential patterns.
与可兴奋膜串联的细胞外电阻（Rs）会导致显著的电压误差，从而扭曲电压钳制膜中的电流记录。本文描述并评估了测量和补偿此类电阻的电学方法。通过响应电流阶跃的传统电压跃变来测量Rs是准确的，但在电压钳制条件下测量正弦波导纳更好，其分辨率（±0.1Ω·cm²）比传统方法提高了约五倍。当大约三分之二的误差被校正时，将膜电流信号进行传统反馈以校正Rs误差信号会导致电压钳制不稳定。我们描述了一种有源电子桥电路，该电路从总膜电流中减去膜电容，并允许对离子电流引起的电压误差进行完全且稳定的补偿。此外，该方法不仅能快速准确地响应指令阶跃控制膜电位，还能在膜电导突然变化后快速恢复。对于几种典型的电位模式，展示了由于对Rs进行完全补偿而导致离子电流的动力学和幅度发生的显著变化。
