Paradox response of frog muscle membrane to changes in external potassium

P. P. Nánási, M. Dankó

Research output: Contribution to journalArticle

5 Citations (Scopus)


Applying conventional microelectrode technique the anomalous behaviour of membrane potential in response to changes in [K+]o was demonstrated in normal and cevadine-treated muscles bathed in Cl--free medium. Partial repolarization of the cevadine-depolarized membrane and reappearance of the slow membrane potential oscillation (SMPO) were induced by elevating [K+]o from 2.5 mM to 10-20 mM. Both effects were reversed by return to 2.5 mM [K+]o. The K-induced repolarization was markedly reduced by 20 mM Cs+, but not by 0.1 mM ouabain, 1 mM 4-aminopyridine, or 1 mM diethyl-pyrocarbonate. The elevation of [K+]o failed to repolarize muscle fibers that had been depolarized only to a small extent. No K-induced repolarization has been observed in Cl--containing fluid. In cevadine-free experiments the omission of potassium from the extracellular space in Cl--free solution hyperpolarized some of the fibers, while depolarized others. Strong electrical stimuli applied in zero K-zero Cl solution turned all the fibers into depolarized state; on returning to 2.5 mM [K+]o complete repolarization was achieved in most of the fibers. It has been concluded that the paradox response of the muscle membrane to changes in [K+]o can be attributed to the K-dependent conductance changes of the inward rectifier K channel providing an explanation for the plateau-formation of SMPO and for the existence of two stable levels of membrane potential of the skeletal muscle bathed in Cl--free medium.

Original languageEnglish
Pages (from-to)157-161
Number of pages5
JournalPflügers Archiv European Journal of Physiology
Issue number2
Publication statusPublished - Jun 1 1989


  • Cevadine
  • Inward rectifier K channel
  • Skeletal muscle
  • Slow membrane potential oscillation
  • Two stable potential levels

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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