The role of negative conductances in neuronal subthreshold properties and synaptic integration

Abstract

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.

Non-Decaying postsynaptics potentials and delayed spikes in hippocampal pyramidal neurons generated by a zero slope conductance created by the persistent Na+ current

“…Nevertheless, we cannot exclude some partial contribution of other negative conductances (e.g. Ca or NMDA) that also prolong the EPSPs [ 1 ] and that are activated in voltages nearby the zero slope conductance region.…”

“…Excitatory postsynaptic potentials (EPSPs) are shaped by subthreshold voltage dependent currents [ 1 ]. The persistent sodium current (I NaP ) is a subthreshold non-inactivating voltage dependent current with a similar voltage-dependence of classical transient sodium current, but with more negative activation potentials.…”

“…The persistent sodium current (I NaP ) is a subthreshold non-inactivating voltage dependent current with a similar voltage-dependence of classical transient sodium current, but with more negative activation potentials. I NaP has a non-monotonic I-V relationship displaying a negative slope conductance (dI/dV) at its activation phase that increases the input resistance and membrane time constant (τ m ) [ 1-3 ]. Moreover, I NaP is generated by the same Na V subunits that produce transient Na + current, and depends on the interaction of the Na V alpha subunit with regulatory beta subunits [ 4 , 5 ].…”

How to build a fast and highly sensitive sound detector that remains robust to temperature shifts

“…Some hair cells tend to be leakier towards the end of recordings. The leak current 371 contributes to cell conductance and affects R in (Ceballos et al, 2017). To exclude the 372 influence of the recording order on R in , we measured R in in another group of hair cells.…”

Dendritic speeding of synaptic potentials in an auditory brainstem principal neuron

“…Surprisingly, the dendrites of the MNTB cell have a high density of Na + channels (Leão et al, 2008). These may boost the EPSP amplitude, but also slow its decay (Leão et al, 2008;Yang et al, 2016;Ceballos et al, 2017).…”