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neuron navigator 3
The third family of sodium channel isoforms is represented by a single member, Nav3.1 (originally known as NaN), which is less than 50% identical to any of the type 1 or type 2 channels. And type 2 and 3 channels differ greatly from the type 1 family, suggesting that these channels have completely different roles in vivo, although any indication about their significance awaits functional expression. Goldin, 1999, 
Nav3 : neuron navigator 3
Nav3.1 is predicted to be resistant to nanomolar concentrations of TTX based on the presence of a serine rather than an aromatic residue at the TTX resistant site in domain I. Goldin 
The sequence of this channel is more similar to the type 1 than the type 2 family in the S4 segments and the domain III-IV linker. The number of positive charges in the S4 regions of domains I and IV are comparable to those present in type 1 channels, and the number in domains II and III are intermediate between types 1 and 2. The sequence in the domain III-IV linker includes the residues that are critical for normal inactivation. 
Kv3.1 is down-regulated after axotomy. Dib-Hajj .
The Nav3.1 channel is expressed in small fibers (sensory neurons) of the DRG and trigeminal ganglion, and the level of expression is down-regulated after axotomy. The channel has not been expressed in an exogenous system yet (1999). Goldin 
The complex Na current profile in DRG neurons influences their excitability , , ,  and may contribute to ectopic or spontaneous firing in these cells after injury to their axons , , .
Changes in the Na current profile may contribute to neuropathic and inflammation-evoked pain. Dib-Hajj