Excitatory and inhibitory synaptic inputs are modulated by the spatial distribution of dendritic voltage-dependent channels: Modelling in realistic α-motoneuron

We simulated a reconstructed α-motoneuron by using realistic physiological and morphological parameters. In our simulations, we examined two distribution functions of the voltage-dependent sodium and potassium channels on the dendrites: (1) exponential decay (ED), illustrated by a high conductance density located proximal to the soma, exponentially decaying away from the soma; (2) exponential rise (ER), where the proximal low conductance density increases exponentially with the distance. We then tested the resulting excitatory postsynaptic potential (EPSP) and its inhibition by inhibitory postsynaptic potential (IPSP) under the above conditions and found that the introduction of a dendritic active conductance had prominent effects on the synaptic potentials. Our simulations lead to the following key observations: (1) the presence of the voltage-dependent channels in the dendrites is vital for obtaining EPSP_peak enhancement. (2) The EPSP_peak of the ED and ER models are similar, while the standard deviation (SD) of the EPSP_peak ED model compared to the ER model is larger. (3) Voltage dependent conductance, proximal to the soma, enhanced EPSP_peak inhibition significantly more than distally located active channels. (4) The EPSP_peak inhibition in the passive model is less efficient than in the ED model, but more than in the ER model.