ERRORS IN PERSISTENT INWARD CURRENTS GENERATED BY SPACE-CLAMP ERRORS - A MODELING STUDY
ERRORS IN PERSISTENT INWARD CURRENTS GENERATED BY SPACE-CLAMP ERRORS - A MODELING STUDY
复制标题
DOI：
10.1152/jn.1995.73.6.2369
复制
发表时间：
1995-06-01
影响因子：
2.5
通讯作者：
KAY, AR
中科院分区：
文献类型：
--
作者：
WHITE, JA;SEKAR, NS;KAY, AR
1.不完善的空间钳失活内向电流的影响进行了检查与使用的“球和棒”的神经元模型具有统一的主动和被动膜特性。由于空间夹持不良，瞬态和稳态（持续性）分量均发生扭曲。在索马测得的稳态电流与峰值电流之比（i（s/p））有时比均匀空间钳的情况小，但通常比均匀空间钳的情况大。对于一个快速的Na+电流，异常的持续性成分是最大的大电紧张性长度，低电导密度，和电压钳电位附近的阈值的电流。在某些条件下，稳态电流可以取两个值之一，这取决于保持电位.膜电位作为距离的函数进行了检查，揭示了稳态电压梯度，其中神经元的远端部分比被动情况下更积极，并且往往比命令电位本身更积极。这些反向的电压梯度，由不受控制的“窗口"Na+电流在远程电紧张距离引起，产生稳态轴向电流如何进入索马，从而增加了持续电流测量体细胞。电流达到峰值的时间（t（p））对空间箝位中的缺陷敏感。这一现象使体细胞膜电流和轴电流在t（p）时对空间钳的保真度也敏感。稳态轴向电流与t = t（p）时轴向电流的比值可以很好地预测i（s/p）的畸变程度.在具有较慢的电压依赖性动力学的模型中，应用相同的原理，但t（p）相对独立于空间钳质量，使得稳态轴向电流的变化在确定i（s/p）中成为更主要的因素。由于这个原因，在慢模型中，i（s/p）随着电导密度的增加而增加，而不是像在快模型中那样收缩。
1. The effects of imperfect space clamp on inactivating inward currents were examined with the use of a ''ball-and-stick'' neuronal model with uniform active and passive membrane properties. With poor space clamp, both transient and steady-state (persistent) components were distorted. The ratio of steady-state to peak current (i(s/p)), measured at the soma, was sometimes smaller but usually larger than would be the case with uniform space clamp. For a fast Na+ current, the anomalous persistent component was largest for large electrotonic lengths, low-conductance densities, and voltage-clamp potentials near the threshold of the current. Under some conditions, steady-state current could take one of two values, depending on the holding potential.2. Membrane potential as a function of distance was examined, revealing a steady-state voltage gradient in which distal portions of the neuron were more positive than in the passive case, and often more positive than the command potential itself. These reversed voltage gradients, caused by the uncontrolled ''window'' Na+ current at remote electrotonic distances, produced steady-state axial current how into the soma, thereby increasing the persistent current measured somatically.3. The time at which the current peaked (t(p)) was sensitive to imperfections in the space clamp. This phenomenon made somatic membrane current and axial current at t(p) sensitive to the fidelity of space clamp as well. The ratio of steady-state axial current to that at t = t(p) was a good predictor of the degree of distortion of i(s/p).4. In a model with slower voltage-dependent kinetics, the same principles applied, but t(p) was relatively independent of space-clamp quality, making changes in the steady-state axial current a more dominant factor in determining i(s/p). For this reason, i(s/p) in the slow model grew with increasing conductance density, instead of shrinking as in the fast model.