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

• Published in: Molecular and cellular neuroscience Vol. 46; no. 1; pp. 159 - 166
• Main Authors: Ho, Cojen, O'Leary, Michael E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2011
• Subjects: Action Potentials - physiology; Animals; Biomarkers - metabolism; Dorsal root ganglia; Female; Ganglia, Spinal - cytology; Ion Channel Gating - physiology; Male; Membrane Potentials - physiology; Necl-1; NF200; Patch-Clamp Techniques; Peripherin; Protein Isoforms - genetics; Protein Isoforms - metabolism; Rats; Sensory Receptor Cells - cytology; Sensory Receptor Cells - metabolism; Single-cell RT-PCR; Sodium channel; Sodium Channel Blockers - metabolism; Sodium Channels - genetics; Sodium Channels - metabolism; Tetrodotoxin - metabolism; Single-cell RT-PCR; NF200; Peripherin; Sodium channel; Dorsal root ganglia; Necl-1
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1016/j.mcn.2010.08.017

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 (<25μm) 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 (>30μm) 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.