Single-cell analysis of sodium channel expression in dorsal root ganglion neurons

Mol Cell Neurosci. 2011 Jan;46(1):159-66. doi: 10.1016/j.mcn.2010.08.017. Epub 2010 Sep 9.

Abstract

Sensory neurons of the dorsal root ganglia (DRG) express multiple voltage-gated sodium (Na) channels that substantially differ in gating kinetics and pharmacology. Small-diameter (<25 μm) neurons isolated from the rat DRG express a combination of fast tetrodotoxin-sensitive (TTX-S) and slow TTX-resistant (TTX-R) Na currents while large-diameter neurons (>30 μm) predominately express fast TTX-S Na current. Na channel expression was further investigated using single-cell RT-PCR to measure the transcripts present in individually harvested DRG neurons. Consistent with cellular electrophysiology, the small neurons expressed transcripts encoding for both TTX-S (Nav1.1, Nav1.2, Nav1.6, and Nav1.7) and TTX-R (Nav1.8 and Nav1.9) Na channels. Nav1.7, Nav1.8 and Nav1.9 were the predominant Na channels expressed in the small neurons. The large neurons highly expressed TTX-S isoforms (Nav1.1, Nav1.6, and Nav1.7) while TTX-R channels were present at comparatively low levels. A unique subpopulation of the large neurons was identified that expressed TTX-R Na current and high levels of Nav1.8 transcript. DRG neurons also displayed substantial differences in the expression of neurofilaments (NF200, peripherin) and Necl-1, a neuronal adhesion molecule involved in myelination. The preferential expression of NF200 and Necl-1 suggests that large-diameter neurons give rise to thick myelinated axons. Small-diameter neurons expressed peripherin, but reduced levels of NF200 and Necl-1, a pattern more consistent with thin unmyelinated axons. Single-cell analysis of Na channel transcripts indicates that TTX-S and TTX-R Na channels are differentially expressed in large myelinated (Nav1.1, Nav1.6, and Nav1.7) and small unmyelinated (Nav1.7, Nav1.8, and Nav1.9) sensory neurons.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Biomarkers / metabolism
  • Female
  • Ganglia, Spinal / cytology*
  • Ion Channel Gating / physiology
  • Male
  • Membrane Potentials / physiology
  • Patch-Clamp Techniques
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Rats
  • Sensory Receptor Cells / cytology
  • Sensory Receptor Cells / metabolism*
  • Sodium Channel Blockers / metabolism
  • Sodium Channels / genetics
  • Sodium Channels / metabolism*
  • Tetrodotoxin / metabolism

Substances

  • Biomarkers
  • Protein Isoforms
  • Sodium Channel Blockers
  • Sodium Channels
  • Tetrodotoxin