The subcellular distribution of T-type Ca2+ channels in interneurons of the lateral geniculate nucleus

PLoS One. 2014 Sep 30;9(9):e107780. doi: 10.1371/journal.pone.0107780. eCollection 2014.

Abstract

Inhibitory interneurons (INs) in the lateral geniculate nucleus (LGN) provide both axonal and dendritic GABA output to thalamocortical relay cells (TCs). Distal parts of the IN dendrites often enter into complex arrangements known as triadic synapses, where the IN dendrite plays a dual role as postsynaptic to retinal input and presynaptic to TC dendrites. Dendritic GABA release can be triggered by retinal input, in a highly localized process that is functionally isolated from the soma, but can also be triggered by somatically elicited Ca(2+)-spikes and possibly by backpropagating action potentials. Ca(2+)-spikes in INs are predominantly mediated by T-type Ca(2+)-channels (T-channels). Due to the complex nature of the dendritic signalling, the function of the IN is likely to depend critically on how T-channels are distributed over the somatodendritic membrane (T-distribution). To study the relationship between the T-distribution and several IN response properties, we here run a series of simulations where we vary the T-distribution in a multicompartmental IN model with a realistic morphology. We find that the somatic response to somatic current injection is facilitated by a high T-channel density in the soma-region. Conversely, a high T-channel density in the distal dendritic region is found to facilitate dendritic signalling in both the outward direction (increases the response in distal dendrites to somatic input) and the inward direction (the soma responds stronger to distal synaptic input). The real T-distribution is likely to reflect a compromise between several neural functions, involving somatic response patterns and dendritic signalling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Animals
  • Calcium Channels, T-Type / metabolism*
  • Calcium Signaling
  • Cell Shape
  • Dendrites / physiology
  • Excitatory Postsynaptic Potentials
  • Geniculate Bodies / cytology*
  • Interneurons / metabolism*
  • Mice
  • Models, Neurological
  • Nerve Net
  • Protein Transport

Substances

  • Calcium Channels, T-Type

Grant support

The project was supported by the Research Council of Norway (ISP-Fysikk, project number 216699; eVITA program, project number 178892), an FP7 EU project (BrainScaleS), and the Norwegian Labour and Welfare Administration. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.