Cs(+) causes a voltage-dependent block of inward K currents in resting skeletal muscle fibres

Nature. 1977 May 12;267(5607):169-70. doi: 10.1038/267169a0.


When frog skeletal muscle fibres are bathed in solutions containing Cs(+) and K(+) in the ratio 1:4,000, a reduction is observed in the size of inward K currents through the resting membrane. This effect is enhanced by an increase in either hyperpolarisation or external Cs(+) concentration. It can be predicted from these findings that regenerative changes in membrane potential should be obtainable in fibres, in the presence of Cs(+), that are hyperpolarised by means of a current electrode. Such responses are described in the last part of this report. In squid axon and frog node, internal Cs(+) produces a voltage-dependent block of the delayed, outward K currents, though the ratio of Cs(+) to K(+) required for this effect is far greater than that used in the experiments reported here. A closer parallel can be drawn between our findings and those recently reported on the inward K currents in the starfish egg cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cesium / metabolism
  • Cesium / pharmacology*
  • Electric Conductivity
  • In Vitro Techniques
  • Ion Channel Gating / drug effects*
  • Kinetics
  • Membrane Potentials / drug effects*
  • Muscle Fibers, Skeletal / drug effects*
  • Muscle Fibers, Skeletal / metabolism
  • Muscle, Skeletal / drug effects*
  • Muscle, Skeletal / metabolism
  • Potassium / metabolism*
  • Potassium / pharmacology
  • Rana temporaria


  • Cesium
  • cesium sulfate
  • Potassium