Slow inactivation of sodium current and voltage-dependent block by tetrodotoxin in rabbit cardiac Purkinje fibers.
The two-microelectrode voltage clamp technique was applied to rabbit cardiac Purkinje fibers in order to study slow inactivation and voltage-dependent block by tetrodotoxin (TTX) of the Na current. The results demonstrate the existence of a slowly inactivating Na current and describe its kinetics and voltage dependence. TTX blocks the slow current in a voltage dependent way: activated and inactivated channels are more sensitive to the toxin. The time course of block of activated channels is dependent on TTX concentration, but in general rather slow. These characteristics illustrate the difference between Na channels in heart and other excitable tissues.
Carmeliet
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D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D004553:Electric Conductivity; D006321:Heart / Q000502:physiology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D012964:Sodium / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology*
D007473:Ion Channels; D013779:Tetrodotoxin; D012964:Sodium