Inward current of the rabbit sinoatrial node cell.
Inward currents of the rabbit sinoatrial node cell were examined in voltage-clamp experiments using the two-microelectrode technique. A fast and slow inward current could be separated from each other. The slow inward current was blocked by Mn and D 600, but it was insensitive to TTX. On the contrary, the fast inward current was blocked by TTX, but not by Mn and D 600. Both the fast and slow inward currents disappeared on Na removal. The fast inward current system was fully inactivated by holding the membrane potential positive to -40 to -50 mV, while the slow inward current system was recorded with the holding potential up to -20 mV. The voltage dependence of the inactivation of the 2 inward current systems and their dependence on [Na]0 suggests that the rising phase of the spontaneous action potential in the S-A node cell is produced mainly by Na current through the slow inward current system.
D000818:Animals; D004594:Electrophysiology; D005711:Gallopamil / Q000494:pharmacology; D066298:In Vitro Techniques; D008345:Manganese / Q000494:pharmacology; D008564:Membrane Potentials; D011817:Rabbits; D012849:Sinoatrial Node / Q000502:physiology*; D012964:Sodium / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
D005711:Gallopamil; D008345:Manganese; D013779:Tetrodotoxin; D012964:Sodium