A novel persistent tetrodotoxin-resistant sodium current in SNS-null and wild-type small primary sensory neurons.

T. R. Cummins, S. D. Dib-Hajj, J. A. Black, A. N. Akopian, J. N. Wood, S. G. Waxman

Research output: Contribution to journalArticle

321 Scopus citations


TTX-resistant (TTX-R) sodium currents are preferentially expressed in small C-type dorsal root ganglion (DRG) neurons, which include nociceptive neurons. Two mRNAs that are predicted to encode TTX-R sodium channels, SNS and NaN, are preferentially expressed in C-type DRG cells. To determine whether there are multiple TTX-R currents in these cells, we used patch-clamp recordings to study sodium currents in SNS-null mice and found a novel persistent voltage-dependent sodium current in small DRG neurons of both SNS-null and wild-type mice. Like SNS currents, this current is highly resistant to TTX (Ki = 39+/-9 microM). In contrast to SNS currents, the threshold for activation of this current is near 70 mV, the midpoint of steady-state inactivation is -44 +/- 1 mV, and the time constant for inactivation is 43+/-4 msec at 20 mV. The presence of this current in SNS-null and wild-type mice demonstrates that a distinct sodium channel isoform, which we suggest to be NaN, underlies this persistent TTX-R current. Importantly, the hyperpolarized voltage-dependence of this current, the substantial overlap of its activation and steady-state inactivation curves and its persistent nature suggest that this current is active near resting potential, where it may play an important role in regulating excitability of primary sensory neurons.

Original languageEnglish (US)
Pages (from-to)RC43
JournalThe Journal of neuroscience : the official journal of the Society for Neuroscience
Issue number24
StatePublished - Dec 15 1999


ASJC Scopus subject areas

  • Neuroscience(all)

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