Comparative study of the distribution of the alpha-subunits of voltage-gated sodium channels in normal and axotomized rat dorsal root ganglion neurons.
We compared the distribution of the alpha-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 alpha-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 GFRalpha1 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.
Fukuoka
Tetsuo
T
Department of Anatomy and Neuroscience, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501, Japan. tfukuoka@hyo-med.ac.jp
Kobayashi
Kimiko
K
Yamanaka
Hiroki
H
Obata
Koichi
K
Dai
Yi
Y
Noguchi
Koichi
K
D000818:Animals; D048429:Cell Size; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors / Q000235:genetics / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D016900:Neurofilament Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020917:Receptor, trkA / Q000378:metabolism; D020812:Receptor, trkC / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*
C494989:Gfra1 protein, rat; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D016900:Neurofilament Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D015222:Sodium Channels; C051774:neurofilament protein H; D006735:Horseradish Peroxidase; D020917:Receptor, trkA; D020812:Receptor, trkC