Table 1.

Implication of TTX-sensitive voltage-gated sodium channels in neuropathic pain.

Channel	Normal Localization [16]	Changes of Expression in Pain States
NaV1.1	-CNS, PNS-Microglia	-Unclear after PNI in NP [16]
NaV1.2	-CNS, very low expression in PNS-SC in lamina I/II	-Unclear after PNI in NP [16]
NaV1.3	-Negligible in DRG (embryonic isoform)-SC in lamina I/II	Upregulated in DRG: CCI [21], PDN [22,23], SNI [24,25], SNL [26,27], traumatic nerve injury (human) [28] Upregulate in painful neuromas (human): [29] Trigeminal ganglion: trigeminal neuropathic pain [30,31,32] Upregulated in sciatic nerve: PDN [33] Upregulated in spinal cord: SCI [34]
NaV1.4	-Skeletal muscle
NaV1.6	-Nodes of Ranvier-SC-PNS-Epidermal free nerve terminals-keratinocytes-Microglia	Upregulated in DRG: PDN [35], lumbar 5 ventral root transection [36], CINP (oxaliplatin) [37] Upregulated in sciatic nerve: CCI [38] Upregulated trigeminal ganglion: trigeminal neuropathic pain [30]
NaV1.7	-PNS in all types of DRG neurons-SC-Epidermal free nerve terminals	Downregulated in DRG: SNL [39], SNI [24,25], traumatic nerve injury (human) [28] Upregulated in DRG: CCI [40], SNI [41], SNL [27], CINP (paclitaxel) [42], cancer-related pain (humans) [42], Herpesvirus quiescent infection [43], painful neuromas (human) [34] Upregulated in spinal cord: CINP (paclitaxel) [42] Upregulated trigeminal ganglion: trigeminal neuropathic pain [44] Upregulated in sciatic nerve: CCI [45]

CINP: chemotherapy-induced neuropathic pain; CNS: central nervous system; DRG: dorsal root ganglia; PNI: peripheral nerve injury; PDN: painful diabetic neuropathy; SCI: Spinal cord injury; SNL: spinal nerve ligation; PNS: peripheral nervous system; SC: spinal cord; CCI: Chronic constriction injury; SNI: spared nerve injury.