Journal
ANNALS OF NEUROLOGY
Volume 65, Issue 6, Pages 733-741Publisher
WILEY-BLACKWELL
DOI: 10.1002/ana.21678
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Funding
- Medical Research Service and Rehabilitation Research Service
- Department of Veterans Affairs
- National Multiple Sclerosis Society [RG-1912]
- Erythromelalgia Association
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Objective: Human and animal Studies have shown that Na(v)1.7 sodium channels, which are preferentially expressed within nociceptors and sympathetic neurons, play a major role in inflammatory and neuropathic pain. Inherited erythromelalgia (IEM) has been linked to gain-of-function Mutations of Na(v)1.7. We now report a novel Mutation (V400M) in a three-generation Canadian family in which pain is relieved by carbamazepine (CBZ). Methods: We extracted genomic DNA from blood samples of eight members of the family, and the sequence of SCN9A coding exons was compared with the reference Na(v)1.7 complementary DNA. Wild-type Na(v)1.7 and V400M cell lines were then analyzed using whole-cell patch-clamp recording for changes in activation, deactivation, steady-state inactivation, and ramp currents. Results: Whole-cell patch-clamp Studies of V400M demonstrate changes in activation, deactivation, steady-stare inactivation, and ramp Currents chat can produce dorsal root ganglia neuron hyperexcitability that underlies pain in these patients. We show that CBZ, at concentrations in the human therapeutic range, normalizes the voltage dependence of activation and inactivation of this inherited erythromelalgia mutation in Na(v)1.7 but does not affect these parameters in wild-type Na(v)1.7. Interpretation: Our results demonstrate a normalizing effect of CBZ on mutant Na(v)1.7 channels in this kindred with CBZ-responsive inherited erythromelalgia. The selective effect of CBZ on the Mutant Na(v)1.7 channel appears to explain the ameliorative response to treatment in this kindred. Our results Suggest that functional expression and pharmacological Studies may provide mechanistic insights into hereditary painful disorders.
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