α-SNS Produces the Slow TTX-Resistant Sodium Current in Large Cutaneous Afferent DRG Neurons

M. Renganathan, Theodore Cummins, W. N. Hormuzdiar, S. G. Waxman

Research output: Contribution to journalArticle

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Abstract

In this study, we used sensory neuron specific (SNS) sodium channel gene knockout (-/-) mice to ask whether SNS sodium channel produces the slow Na+ current ('slow') in large (>40 μm diam) cutaneous afferent dorsal root ganglion (DRG) neurons. SNS wild-type (+/+) mice were used as controls. Retrograde Fluoro-Gold labeling permitted the definitive identification of cutaneous afferent neurons. Prepulse inactivation was used to separate the fast and slow Na+ currents. Fifty-two percent of the large cutaneous afferent neurons isolated from SNS (+/+) mice expressed only fast-inactivating Na+ currents ('fast'), and 48% expressed both fast and slow Na+ currents. The fast and slow current densities were 0.90 ± 0.12 and 0.39 ± 0.16 nA/pF, respectively. Fast Na+ currents were blocked completely by 300 nM tetrodotoxin (TTX), while slow Na+ currents were resistant to 300 nM TTX, confirming that the slow Na+ currents observed in large cutaneous DRG neurons are TTX-resistant (TTX-R). Slow Na+ currents could not be detected in large cutaneous afferent neurons from SNS (-/-) mice; these cells expressed only fast Na+ current, and it was blocked by 300 nM TTX. The fast Na+ current density in SNS (-/-) neurons was 1.47 ± 0.14 nA/pF, approximately 60% higher than the current density observed in SNS (+/+) mice (P <0.02). A low-voltage-activated TTX-R Na+ current ('persistent') observed in small C-type neurons is not present in large cutaneous afferent neurons from either SNS (+/+) or SNS (-/-) mice. These results show that the slow TTX-R Na+ current in large cutaneous afferent DRG is produced by the SNS sodium channel.

Original languageEnglish (US)
Pages (from-to)710-718
Number of pages9
JournalJournal of Neurophysiology
Volume84
Issue number2
StatePublished - 2000
Externally publishedYes

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Tetrodotoxin
Spinal Ganglia
Sensory Receptor Cells
Sodium
Neurons
Skin
Afferent Neurons
Sodium Channels
Gene Knockout Techniques
Knockout Mice

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

Cite this

α-SNS Produces the Slow TTX-Resistant Sodium Current in Large Cutaneous Afferent DRG Neurons. / Renganathan, M.; Cummins, Theodore; Hormuzdiar, W. N.; Waxman, S. G.

In: Journal of Neurophysiology, Vol. 84, No. 2, 2000, p. 710-718.

Research output: Contribution to journalArticle

Renganathan, M. ; Cummins, Theodore ; Hormuzdiar, W. N. ; Waxman, S. G. / α-SNS Produces the Slow TTX-Resistant Sodium Current in Large Cutaneous Afferent DRG Neurons. In: Journal of Neurophysiology. 2000 ; Vol. 84, No. 2. pp. 710-718.
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