Plasticity of sodium channel expression in DRG neurons in the chronic constriction injury model of neuropathic pain

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Abstract
Rrents that are resistant to tetrodotoxin (TTX-R) and the transcripts of two TTX-R sodium channels are significantly attenuated, while a rapidly repriming tetrodotoxin-sensitive (TTX-S) current emerges and the transcripts of α-III sodium channel, which produce a TTX-S current when expressed in oocytes, are up-regulated. We report here on changes in sodium currents and sodium channel transcripts in DRG neurons in the chronic constriction injury (CCI) model of neuropathic pain. CCI-induced changes in DRG neurons, 14 days post-surgery, mirror those of axotomy. Transcripts of NaN and SNS, two sensory neuron-specific TTX-R sodium channels, are significantly down-regulated as is the TTX-R sodium current, while transcripts of the TTX-S α-III sodium channel and a rapidly repriming TTX-S Na current are up-regulated in small diameter DRG neurons. These changes may provide at least a partial basis for the hyperexcitablity of DRG neurons that contributes to hyperalgesia in this model....