Nitric oxide blocks fast, slow, and persistent Na+ channels in C-type DRG neurons by S-nitrosylation.
C-type dorsal root ganglion (DRG) neurons express three types of Na+ currents: fast TTX-sensitive, slow TTX-resistant, and persistent TTX-resistant Na+ currents. The nitric oxide (NO) donors papa-NONOate and S-nitroso-N-acetyl-DL-penicillamine inhibit all three types of Na+ currents. The NO scavenger hemoglobin abolished the effects of papa-NONOate on Na+ currents, indicating that NO or NO-related species inhibit these Na+ currents. NO donor inhibition of all three types of Na+ currents was reversed by washout. Incubation of neurons with 8-bromo cGMP, a membrane-permeable analogue of cGMP, and cG-PKI, an inhibitor of cGMP-dependent protein kinase, had no effect on papa-NONOate-mediated Na+ current block, demonstrating that Na+ current inhibition is independent of cGMP. Alkylation of free thiols with N-ethylmaleimide prevented the actions of papa-NONOate, suggesting that NO, or a related reactive nitrogen species, modifies sulfhydryl groups on Na+ channels or a closely associated protein. Papa-NONOate-mediated block of Na+ currents is not due to a hyperpolarizing shift in steady state voltage-dependent inactivation. The absence of NO-mediated enhancement of slow inactivation in fast and slow Na+ channels indicates that NO does not inhibit fast and slow Na+ channels by facilitating the transition to a slow inactivated state. These results demonstrate that inhibition of Na+ currents is not due to the modulation of fast and slow sodium channel inactivation. Taken together, these results show that NO or NO-related products modify the sulfhydryl groups on Na+ channels and inhibit Na+ currents by blocking the channel conductance.
Renganathan
M
M
Department of Neurology and Paralyzed Veterans Association/Eastern Paralyzed Veterans Association Neuroscience Research Center, Yale Medical School, 333 Cedar Street, New Haven, CT 06510, USA.
Cummins
T R
TR
Waxman
Stephen G
SG
D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D004594:Electrophysiology; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D006454:Hemoglobins / Q000494:pharmacology; D006834:Hydrazines / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009412:Nerve Fibers / Q000378:metabolism*; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009584:Nitrogen / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D000779:Anesthetics, Local; D006454:Hemoglobins; D006834:Hydrazines; D020030:Nitric Oxide Donors; C112653:PAPA NONOate; D015222:Sodium Channels; D009569:Nitric Oxide; D013779:Tetrodotoxin; D013455:Sulfur; D012964:Sodium; D009584:Nitrogen