Tetrodotoxin-resistant sodium channels Nav1.8/SNS and Nav1.9/NaN in afferent neurons innervating urinary bladder in control and spinal cord injured rats

Joel A. Black, Theodore R. Cummins, Naoki Yoshimura, William C. De Groat, Stephen G. Waxman

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43 Scopus citations


Tetrodotoxin-resistant (TTX-R) sodium channels Nav1.8/SNS and Nav1.9/NaN are preferentially expressed in small diameter dorsal root ganglia (DRG) neurons. The urinary bladder is innervated by small afferent neurons from L6/S1 DRG, of which ∼75% exhibit high-threshold action potentials that are mediated by TTX-R sodium channels. Following transection of the spinal cord at T8, the bladder becomes areflexic and then gradually hyper-reflexic, and there is an attenuation of the TTX-R sodium currents in bladder afferent neurons. In the present study, we demonstrate that Nav1.8 is expressed in both bladder and non-bladder afferent neurons, while Nav1.9 is expressed in non-bladder afferent neurons but is rarely observed in bladder afferent neurons. In spinal cord transected rats 28-32 days following transection, there is a decreased expression of Nav1.8 sodium channels in bladder afferents, but no change in the expression of Nav1.8 in non-bladder afferent neurons. Both bladder and non-bladder afferent neurons exhibit limited increases in Nav1.9 expression following spinal cord transection. These results demonstrate that the expression of TTX-R channels in bladder afferent neurons changes after spinal cord transection, and these changes may contribute to the increased excitability of these neurons following spinal cord injury.

Original languageEnglish (US)
Pages (from-to)132-138
Number of pages7
JournalBrain research
Issue number1-2
StatePublished - Feb 14 2003



  • Bladder
  • Dorsal root ganglia
  • Sodium channel
  • Spinal cord
  • Spinal cord injury

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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