Sodium current kinetics in cat atrial myocytes.
1. Na+ current kinetics were studied in isolated atrial myocytes from the adult cat using the single suction-pipette voltage-clamp technique. 2. Current-voltage and conductance-voltage relationships were similar to those described in other cardiac myocyte preparations. 3. Analysis of Na+ current decay using single-pulse, double-pulse and tail current measurements were in agreement and demonstrate a second-order process of current decay. 4. Voltage dependence of steady-state inactivation curves was not symmetrical, having an inflexion at about -90 mV. These results suggest more than a single inactivation process for Na+ channel in the negative potential region. 5. Recovery of Na+ current from inactivation had a sigmoid time course: an initial slow component (delay) followed by a fast and then a second slow component. Increasing the pre-pulse duration slowed the time course of recovery. 6. Taken together, the results were consistent with the presence of multiple inactivated states for the atrial myocyte Na+ channel.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D002478:Cells, Cultured; D006321:Heart / Q000502:physiology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D007473:Ion Channels; D013779:Tetrodotoxin; D012964:Sodium