Mediates the voltage-dependent sodium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a sodium-selective channel through which Na(+) ions may pass in accordance with their electrochemical gradient (    ). It is a tetrodotoxin-sensitive Na(+) channel isoform . Plays a role in pain mechanisms, especially in the development of inflammatory pain ( , ).
Subcellular locations: Cell membrane, Cell projection, Neuron projection
In neurite terminals.
Expressed strongly in dorsal root ganglion, with only minor levels elsewhere in the body, smooth muscle cells, MTC cell line and C-cell carcinoma. Also expressed in vagus nerves within the head and neck region . Isoform 1 is expressed preferentially in the central and peripheral nervous system. Isoform 2 is expressed preferentially in the dorsal root ganglion.