Electrophysiological characterization of a TTX-sensitive sodium current in native Xenopus oocytes.
We have studied a fast inward current expressed in oocytes from one Xenopus laevis. This current was characterized as a sodium current. It was activated by depolarizations to -50 mV or higher, peaked within 3-5 ms, and then decayed following a mono-exponential timecourse. When clamped at different holding potentials, the current displayed voltage-dependent inactivation with a V0.5 of -51 mV. The channel responsible for this Na+ entry was blocked by tetrodotoxin with a K0.5 of 8 nM, and was resistant to block by lidocaine at concentrations up to 100 microM. The pharmacological similarities between neuronal and oocyte sodium channels suggest that the two channels share a conserved structure.
CRBM, CNRS (UPR9008)-INSERM (U249), Montpellier, France.
E
E
Bourinet
J
J
Nargeot
P
P
Charnet
D000818:Animals; D004594:Electrophysiology / Q000379:methods; D005260:Female; D007700:Kinetics; D008012:Lidocaine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology*; D013997:Time Factors; D014982:Xenopus laevis
D015222:Sodium Channels; D013779:Tetrodotoxin; D008012:Lidocaine; D012964:Sodium