Properties of the current if in the sino-atrial node of the rabbit compared with those of the current iK, in Purkinje fibres

J Physiol. 1980 Nov:308:353-67. doi: 10.1113/jphysiol.1980.sp013475.


1. Properties of the 'pace-maker' current if in rabbit sino-atrial node have been investigated by voltage clamp of small preparations and compared with those of the iK2 current in the Purkinje fibre. Besides having a similar voltage range of activation and responding in a similar way to adrenaline, if resembles iK2 in other respects. 2. When external Na is reduced, if decreases proportionally. In 25% Na the time-dependent current change due to if disappears. 3. 20 mM-Cs completely abolishes it. 4. The time constant of if during a hyperpolarizing voltage-clamp pulse displays a relatively high temperature dependence. 5. In spite of the similarities between the two current systems, experiments in high K solutions (48 mM) rule out the possibility that the current change seen on a hyperpolarization reflects the decay of a pure K current. 6. From conductance measurements during onset of if it is deduced that if behaves as an inward current activated by hyperpolarizations.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cesium / pharmacology
  • Electric Conductivity
  • Heart Conduction System / physiology*
  • In Vitro Techniques
  • Ion Channels / drug effects
  • Kinetics
  • Membrane Potentials
  • Potassium / pharmacology
  • Purkinje Fibers / physiology*
  • Rabbits
  • Sinoatrial Node / physiology*
  • Sodium / pharmacology
  • Temperature


  • Ion Channels
  • Cesium
  • Sodium
  • Potassium