Molecular identities of two tetrodotoxin-resistant sodium channels in corneal axons.
Previous electrophysiological studies have demonstrated that tetrodotoxin-resistant (TTX-R) sodium channels contribute to action potential electrogenesis and conduction along non-myelinated PNS axons. Moreover, recent work has established that TTX-R sodium channels play a major role in the generation of action potentials in the terminals of non-myelinated nociceptive axons innervating the cornea. We have utilized subtype-specific antibodies to sodium channels Na(v)1.8 and Na(v)1.9 to examine the molecular identity of the TTX-R sodium channels that are present in these axons. Both Na(v)1.8 and Na(v)1.9 sodium channels are expressed diffusely along the entire lengths of non-myelinated corneal axons, from the nerve plexus at the corneoscleral limbus to the distal corneal leash fibers. Moreover, both Na(v)1.8 and Na(v)1.9 are localized at the bulb-like nerve terminals of the leash fibers within the superficial epithelial layers of the cornea. These observations suggest that both TTX-R sodium channels Na(v)1.8 and Na(v)1.9 contribute to the electrogenesis of non-myelinated axons of the cornea.
Black
Joel A
JA
Department of Neurology and Paralyzed Veterans of America/Eastern Paralyzed Veterans Association Neuroscience Research Center, Yale University School of Medicine, New Haven, CT 06510, USA. joel.black@yale.edu
Waxman
Stephen G
SG
D000200:Action Potentials; D000818:Animals; D000906:Antibodies; D001369:Axons / Q000276:immunology / Q000378:metabolism*; D003315:Cornea / Q000276:immunology / Q000294:innervation* / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008297:Male; D018613:Microscopy, Confocal; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000276:immunology / Q000378:metabolism*; D013779:Tetrodotoxin / Q000378:metabolism*
D000906:Antibodies; D015222:Sodium Channels; D013779:Tetrodotoxin