Jackson M B
Department of Physiology, University of Wisconsin Medical School, Madison 53706.
Biophys J. 1992 Mar;61(3):756-66. doi: 10.1016/S0006-3495(92)81880-5.
A theoretical analysis was undertaken of a Rall motoneuron under voltage clamp with a finite access resistance. This model is relevant to the conditions of the whole-cell patch clamp, which to date has been used very little for cable analysis. It was shown that the soma and cable charging currents can be distinguished, and that the soma is charged with a time constant approximately equal to the access resistance times the somatic capacitance. Thus, the charging time of the soma is similar to what it would be if the cell had no process. Simple formulas were derived that can be used to calculate the electrotonic length, the membrane time constant, and the soma-dendrite resistance ratio of a cell with a cylindrical process. With the aid of these formulas, reasonable estimates of parameter values were recovered from simulated transient currents. Tests of the Rall model were proposed to determine when there is an equivalent cylinder that is consistent with observed charging behavior. The analysis was extended to a cable with an open end and to a model in which the soma and dendrite have different membrane time constants. It was shown that with voltage-clamp data estimates of electrical parameters other than rho are relatively insensitive to differences between the membrane properties of the soma and dendrite. The methods of cable analysis introduced here were illustrated by application to charging transients recorded from a hippocampal pyramidal cell and from a neurohypophysial nerve ending. The Rall model provided a good description of the pyramidal cell current transient but was inconsistent with the charging behavior observed for the nerve ending. With the recent technical advance of patch clamp recording in brain slices, the analysis presented here should help neurophysiologists investigate cable properties in a wide variety of systems.
对具有有限接入电阻的电压钳制下的秧鸡运动神经元进行了理论分析。该模型与全细胞膜片钳的条件相关，迄今为止，全细胞膜片钳在电缆分析中使用得很少。结果表明，可以区分胞体和电缆充电电流，并且胞体充电的时间常数近似等于接入电阻乘以胞体电容。因此，胞体的充电时间与细胞没有突起时的情况相似。推导了简单的公式，可用于计算具有圆柱形突起的细胞的电紧张长度、膜时间常数和胞体 - 树突电阻比。借助这些公式，从模拟瞬态电流中恢复了参数值的合理估计。提出了对拉尔模型的测试，以确定何时存在与观察到的充电行为一致的等效圆柱体。分析扩展到了具有开放端的电缆以及胞体和树突具有不同膜时间常数的模型。结果表明，利用电压钳数据，除了ρ之外的电参数估计对胞体和树突膜特性之间的差异相对不敏感。通过应用于从海马锥体细胞和神经垂体神经末梢记录的充电瞬变，说明了这里介绍的电缆分析方法。拉尔模型对锥体细胞电流瞬变提供了很好的描述，但与神经末梢观察到的充电行为不一致。随着最近脑片膜片钳记录技术的进步，这里提出的分析应该有助于神经生理学家研究各种系统中的电缆特性。
