Ceballos Cesar C, Roque Antonio C, Leão Ricardo M
Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Department of Physics, School of Philosophy, Sciences and Letters, University of São Paulo, Ribeirão Preto, Brazil.
Biophys Rev. 2017 Oct;9(5):827-834. doi: 10.1007/s12551-017-0300-8. Epub 2017 Aug 14.
Based on passive cable theory, an increase in membrane conductance produces a decrease in the membrane time constant and input resistance. Unlike the classical leak currents, voltage-dependent currents have a nonlinear behavior which can create regions of negative conductance, despite the increase in membrane conductance (permeability). This negative conductance opposes the effects of the passive membrane conductance on the membrane input resistance and time constant, increasing their values and thereby substantially affecting the amplitude and time course of postsynaptic potentials at the voltage range of the negative conductance. This paradoxical effect has been described for three types of voltage-dependent inward currents: persistent sodium currents, L- and T-type calcium currents and ligand-gated glutamatergic N-methyl-D-aspartate currents. In this review, we describe the impact of the creation of a negative conductance region by these currents on neuronal membrane properties and synaptic integration. We also discuss recent contributions of the quasi-active cable approximation, an extension of the passive cable theory that includes voltage-dependent currents, and its effects on neuronal subthreshold properties.
基于被动电缆理论，膜电导的增加会导致膜时间常数和输入电阻减小。与经典的泄漏电流不同，电压依赖性电流具有非线性行为，尽管膜电导（通透性）增加，但仍会产生负电导区域。这种负电导会对抗被动膜电导对膜输入电阻和时间常数的影响，增加它们的值，从而在负电导的电压范围内显著影响突触后电位的幅度和时间进程。这种矛盾的效应已在三种类型的电压依赖性内向电流中得到描述：持续性钠电流、L型和T型钙电流以及配体门控谷氨酸能N-甲基-D-天冬氨酸电流。在本综述中，我们描述了这些电流产生的负电导区域对神经元膜特性和突触整合的影响。我们还讨论了准主动电缆近似的最新贡献，它是被动电缆理论的扩展，包括电压依赖性电流，及其对神经元阈下特性的影响。
