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(NAS Colloquium) The Neurobiology of Pain (1999) / Chapter Skim
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Sodium Channels and Pain
Pages 7635-7639

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From page 7635...
... Early studies demonstrated that, after injury to their axons, neurons can display changes in excitability, suggesting increased sodium channel expression, and, in fact, abnormal sodium channel accumulation has been observed at the tips of injured axons. We have used an ensemble of molecular, electrophysiological, and pharmacological techniques to ask: what types of sodium channels underlie hyperexcitability of primary sensory neurons after injury?
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From page 7636...
... PNl and NaG also may represent useful molecular targets for the pharmacologic manipulation of DRG neurons because of their preferential expression in these cells. Sodium Channel Gene Expression Is Altered After Injury to DRG Neurons The first observations indicating that, in addition to production of excess channels, there is a switch in the type of channels produced after axonal injury were provided by Waxman et al.
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From page 7637...
... , loss of TTX-resistant currents in DRG neurons after axotomy could produce a hyperpolarizing shift in resting potential, which, by relieving resting inactivation, might increase the amount of TTX-sensitive sodium current available for electrogenesis. Neurotrophins Modulate Sodium Channel Expression in DRG Neurons A number of studies have suggested that, in response to nerve or tissue injury, there are changes in synthesis or delivery of various neurotrophins to neurons.
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From page 7638...
... Interestingly, NGF normally is produced in peripheral target tissues by supporting cells that include fibroblasts, Schwann cells, and keratinocytes; NGF production is stimulated in immune cells, and increased NGF levels have been observed in the local area after treatment with inflammatory agents such as carageenan and Freund's adjuvant (51, 52) , raising the possibility that inflammation may indirectly trigger changes in sodium channel gene expression via changes in neurotrophin levels.
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From page 7639...
... This observation may present a therapeutic opportunity for the selective manipulation of primary sensory neurons in general, or nociceptive neurons in particular. Fourth, sodium channel expression in DRG neurons is highly dynamic, with multiple sodium channel genes (including or-III, SNS/PN3, and NaN)
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Key Terms

  • sodium channel
  • sodium channels
  • channel expression
  • sodium currents
  • sodium current

  • channel gene
  • sensory neurons
  • primary sensory
  • channel genes
  • preferential expression

  • growth factor
  • multiple sodium
  • sensory neuron
  • axotomized drg
  • axonal transection

  • expressed preferentially
  • action potential
  • mrna levels
  • mrna expression
  • previously silent

  • nociceptive cells
  • increased sodium
  • channel accumulation
  • highly dynamic
  • significantly increased

  • partial rescue
  • neurons express
  • nerve stump
  • neurons projecting
  • root ganglion


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