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Pflügers Archiv

, Volume 407, Issue 2, pp 199–203 | Cite as

The apamin-sensitive potassium current in frog skeletal muscle: its dependence on the extracellular calcium and sensitivity to calcium channel blockers

  • Flavien Traoré
  • Christian Cognard
  • Daniel Potreau
  • Guy Raymond
Excitable Tissues and Central Nervous Physiology

Abstract

Slow outward potassium currents were recorded in isolated frog skeletal muscle fibres using the double mannitol-gap voltage-clamp technique.

Detubulated fibres failed to generate a slow outward current, and apamin had no effect on the remaining current.

The maximum blocking effect of organic and inorganic Ca2+-channel blockers on the slow outward channels of intact fibres was larger than that of apamin. Apamin failed to induce an additional block when applied after Ca2+-channel blockers.

In a low-Ca2+ solution (OCa, EGTA 1 mM) the slow outward current was slightly increased and the blocking effect of apamin was enhanced. A Ca2+-rich solution (Ca2+×10) increased the slow outward current and the blocking effect of apamin was drastically reduced.

It is concluded that the apamin-sensitive current which is a component of the slow outward K+ current is located in the tubular membrane. Its activation seems barely dependent on the Ca2+ influx via the slow inward Ca2+ current. Apamin-receptor binding appears to be dependent on the extracellular Ca2+ concentration. Blockade of slow outward current by Ca2+-channel blockers is likely to be the result of a direct action on the slow K+ permeability rather than a consequence of Ca2+ channel inhibition.

Key words

Ca2+-dependent K+ permeability Ca2+-channel blockers Apamin Voltage-clamp Skeletal muscle 

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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • Flavien Traoré
    • 1
  • Christian Cognard
    • 1
  • Daniel Potreau
    • 1
  • Guy Raymond
    • 1
  1. 1.Laboratory of General Physiology, U.A. C.N.R.S. no. 290, Faculty of SciencesUniversity of PoitiersPoitiers CedexFrance

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