The steady state TTX-sensitive ("window") sodium current in cardiac Purkinje fibres

David Attwell, Ira Cohen, David Eisner, Mitsuyoshi Ohba, Carlos Ojeda

    Research output: Contribution to journalArticlepeer-review


    Voltage clamp experiments on isolated sheep Purkinje fibres showed an increase of the steady state outward membrane current, over the potential range -65 mV to -15 mV, in the presence of tetrodotoxin (TTX, 3 · 10-5 M). This "window" current is considered to be the steady state component of the fast sodium current (INa), resulting from the crossover of the activation and inactivation curves which govern the opening of the sodium channel. TTX had no significant effect on the reversal potential, activation curve, kinetics or instantaneous I-V relationship of the pacemaker current IK2. The window found in these experiments extends to potentials well into the range of the action potential plateau. Consequently small changes of the steady state INa might have large effects on the action potential duration. The effects of TTX and local anaesthetics are discussed in this context. © 1979 Springer-Verlag.
    Original languageEnglish
    Pages (from-to)137-142
    Number of pages5
    JournalPflügers Archiv European Journal of Physiology
    Issue number2
    Publication statusPublished - Mar 1979


    • Action potential duration
    • Purkinje fibre
    • Sodium current
    • Tetrodotoxin
    • Voltage clamp


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