Backpropagation of the δ oscillation and the retinal excitatory postsynaptic potential in a multi-compartment model of thalamocortical neurons

Z. Emri, K. Antal, T. I. Tóth, D. W. Cope, V. Crunelli

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Abstract

Uniform and non-uniform somato-dendritic distributions of the ion channels carrying the low-threshold Ca2+ current (I(T)), the hyperpolarization-activated inward current (I(h)), the fast Na+ current (I(Na)) and the delayed rectifier current (I(K)) were investigated in a multi-compartment model of a thalamocortical neuron for their suitability to reproduce the δ oscillation and the retinal excitatory post-synaptic potential recorded in vitro from the soma of thalamocortical neurons. The backpropagation of these simulated activities along the dendritic tree was also studied.A uniform somato-dendritic distribution of the maximal conductance of I(T) and I(K) (g(T) and g(K), respectively) was sufficient to simulate with acceptable accuracy: (i) the δ oscillation, and its phase resetting by somatically injected current pulses; as well as (ii) the retinal excitatory postsynaptic potential, and its α-amino-3-hydroxy-5-methyl-4-isoxazole proprionate and/or N-methyl-D-aspartate components. In addition, simulations where the dendritic g(T) and g(K) were either reduced (both by up to 34%) or increased (both by up to 15%) of their respective value on the soma still admitted a successful reproduction of the experimental activity. When the dendritic distributions were non-uniform, models where the proximal and distal dendritic g(T) was up to 1.8- and 1.2-fold larger, respectively, than g(T(s)) produced accurate simulations of the δ oscillation (and its phase resetting curves) as well as the synaptic potentials without need of a concomitant increase in proximal or distal dendritic g(K). Furthermore, an increase in proximal dendritic g(T) and g(K) of up to fourfold their respective value on the soma resulted in acceptable simulation results.Addition of dendritic Na+ channels to the uniformly or non-uniformly distributed somato-dendritic T-type Ca2+ and K+ channels did not further improve the overall qualitative and quantitative accuracy of the simulations, except for increasing the number of action potentials in bursts elicited by low-threshold Ca2+ potentials. Dendritic I(h) failed to produce a marked effect on the simulated δ oscillation and the excitatory postsynaptic potential.In the presence of uniform and non-uniform dendritic g(T) and g(K), the δ oscillation propagated from the soma to the distal dendrites with no change in frequency and voltage-dependence, though the dendritic action potential amplitude was gradually reduced towards the distal dendrites. The amplitude and rising time of the simulated retinal excitatory postsynaptic potential were only slightly decreased during their propagation from their proximal dendritic site of origin to the soma or the distal dendrites.These results indicate that a multi-compartment model with passive dendrites cannot fully reproduce the experimental activity of thalamocortical neurons, while both uniform and non-uniform somato-dendritic g(T) and g(K) distributions are compatible with the properties of the δ oscillation and the retinal excitatory postsynaptic potential recorded in vitro from the soma of these neurons. Furthermore, by predicting the existence of backpropagation of low-threshold Ca2+ potentials and retinal postsynaptic potentials up to the distal dendrites, our findings suggest a putative role for the δ oscillation in the dendritic processing of neuronal activity, and support previous hypotheses on the interaction between retinal and cortical excitatory postsynaptic potentials on thalamocortical neuron dendrites. Copyright (C) 2000 Elsevier Science Ltd.

Original languageEnglish
Pages (from-to)111-127
Number of pages17
JournalNeuroscience
Volume98
Issue number1
DOIs
Publication statusPublished - Jun 1 2000

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Keywords

  • Action potential
  • Dendritic channels
  • Dendritic propagation
  • Low-threshold Ca current
  • NMDA/AMPA-mediated EPSP

ASJC Scopus subject areas

  • Neuroscience(all)

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