Voltage-gated Na+ channels (Nav) are essential for the generation of action potentials and for cell excitability1. Nav channels are activated in response to depolarization and selectively allow flow of Na+ ions. To date, nine Nav α subunits have been cloned and named Nav1.1-1.9. The Nav channels are classified into two groups according to their sensitivity to tetrodotoxin (TTX): TTX-sensitive and TTX-resistant channels4,5. The expression of the α subunit isoform is developmentally regulated and tissue specific.nTwo TTX-resistant Nav channels are expressed in dorsal root ganglion (DRG) neurons, Nav1.8 and Nav1.9. The Nav1.8 channel (also called SNS, SCN10A and PN3) is mainly expressed in small-diameter DRG neurons. TTX-resistant channels have been suggested to play an important role in nociceptive transmission. Recently, involvement of Nav1.8 in multiple sclerosis (MS) was suggested due to up-regulation of both, mRNA and protein, in Purkinje cells of MS patients and also in animal models.
