Background：

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. Plays a key role in brain， probably by regulating the moment when neurotransmitters are released in neurons. Involved in sensory perception of mechanical pain: activation in somatosensory neurons induces pain without neurogenic inflammation and produces hypersensitivity to mechanical， but not thermal stimuli.