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Comparative study of the distribution of the α‐subunits of voltage‐gated sodium channels in normal and axotomized rat dorsal root ganglion neurons
Author(s) -
Fukuoka Tetsuo,
Kobayashi Kimiko,
Yamanaka Hiroki,
Obata Koichi,
Dai Yi,
Noguchi Koichi
Publication year - 2008
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.21786
Subject(s) - dorsal root ganglion , biology , sodium channel , neuroscience , dorsum , ganglion , anatomy , sodium , chemistry , organic chemistry
We compared the distribution of the α‐subunit mRNAs of voltage‐gated sodium channels Nav1.1–1.3 and Nav1.6–1.9 and a related channel, Nax, in histochemically identified neuronal subpopulations of the rat dorsal root ganglia (DRG). In the naïve DRG, the expression of Nav1.1 and Nav1.6 was restricted to A‐fiber neurons, and they were preferentially expressed by TrkC neurons, suggesting that proprioceptive neurons possess these channels. Nav1.7, ‐1.8, and ‐1.9 mRNAs were more abundant in C‐fiber neurons compared with A‐fiber ones. Nax was evenly expressed in both populations. Although Nav1.8 and ‐1.9 were preferentially expressed by TrkA neurons, other α‐subunits were expressed independently of TrkA expression. Actually, all IB4 + neurons expressed both Nav1.8 and ‐1.9, and relatively limited subpopulations of IB4 + neurons (3% and 12%, respectively) expressed Nav1.1 and/or Nav1.6. These findings provide useful information in interpreting the electrophysiological characteristics of some neuronal subpopulations of naïve DRG. After L5 spinal nerve ligation, Nav1.3 mRNA was up‐regulated mainly in A‐fiber neurons in the ipsilateral L5 DRG. Although previous studies demonstrated that nerve growth factor (NGF) and glial cell‐derived neurotrophic factor (GDNF) reversed this up‐regulation, the Nav1.3 induction was independent of either TrkA or GFRα1 expression, suggesting that the induction of Nav1.3 may be one of the common responses of axotomized DRG neurons without a direct relationship to NGF/GDNF supply. J. Comp. Neurol. 510:188–206, 2008. © 2008 Wiley‐Liss, Inc.