Resurgent-like currents in mouse vas deferens myocytes are mediated by NaV1.6 voltage-gated sodium channels

• Published in: Pflügers Archiv 2012-11, Vol.464 (5), p.493-502
• Main Authors: Teramoto, Noriyoshi, Zhu, Hai-Lei, Yotsu-Yamashita, Mari, Inai, Tetsuichiro, Cunnane, Thomas C.
• Format: Article
• Language: English
• Subjects: Action Potentials - genetics; Animals; Biomedical and Life Sciences; Biomedicine; Cell Biology; Human Physiology; Insect Proteins - pharmacology; Male; Mice; Mice, Mutant Strains; Molecular Medicine; Muscle Physiology; Myocytes, Smooth Muscle - physiology; NAV1.6 Voltage-Gated Sodium Channel - drug effects; NAV1.6 Voltage-Gated Sodium Channel - genetics; NAV1.6 Voltage-Gated Sodium Channel - physiology; Neurosciences; Receptors; Tetrodotoxin - pharmacology; Vas Deferens - cytology; Voltage-Gated Sodium Channel Agonists - pharmacology; Voltage-Gated Sodium Channel Blockers - pharmacology; Wasp Venoms - pharmacology
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s00424-012-1153-4

Patch-clamp experiments were performed to investigate the molecular properties of resurgent-like currents in single smooth muscle cells dispersed from mouse vas deferens, utilizing both Na V 1.6-null mice (Na V 1.6 −/− ), lacking the expression of the Scn8a Na + channel gene, and their wild-type littermates (Na V 1.6 +/+ ). Na V 1.6 immunoreactivity was clearly visible in dispersed smooth muscle cells obtained from Na V 1.6 +/+ , but not Na V 1.6 −/− , vas deferens. Following a depolarization to +30 mV from a holding potential of −70 mV (to produce maximal inactivation of the Na + current), repolarization to voltages between −60 and +20 mV elicited a tetrodotoxin (TTX)-sensitive inward current in Na V 1.6 +/+ , but not Na V 1.6 −/− , vas deferens myocytes. The resurgent-like current in Na V 1.6 +/+ vas deferens myocytes peaked at approximately −20 mV in the current–voltage relationship. The peak amplitude of the resurgent-like current remained at a constant level when the membrane potential was repolarized to −20 mV following the application of depolarizing rectangular pulses to more positive potentials than +20 mV. 4,9-Anhydrotetrodotoxin (4,9-anhydroTTX), a selective Na V 1.6 blocking toxin, purified from a crude mixture of TTX analogues by LC-FLD techniques, reversibly suppressed the resurgent-like currents. β-Pompilidotoxin, a voltage-gated Na + channel activator, evoked sustained resurgent-like currents in Na V 1.6 +/+ but not Na V 1.6 −/− murine vas deferens myocytes. These results strongly indicate that, primarily, resurgent-like currents are generated as a result of Na V 1.6 channel activity.