Evidence for two K+ currents activated upon hyperpolarization of Paramecium tetraurelia

The Journal of Membrane Biology
R R PrestonC Kung

Abstract

Hyperpolarization of voltage-clamped Paramecium tetraurelia in K+ solutions elicits a complex of Ca2+ and K+ currents. The tail current that accompanies a return to holding potential (-40 mV) contains two K+ components. The tail current elicited by a step to -110 mV of greater than or equal to 50-msec duration contains fast-decaying (tau approximately 3.5 msec) and slow-decaying (tau approximately 20 msec) components. The reversal potential of both components shifts by 55-57 mV/10-fold change in external [K+], suggesting that they represent pure K+ currents. The dependence of the relative amplitudes of the two tail currents on duration of hyperpolarization suggests that the slow K+ current activates slowly and is sustained, whereas the fast current activates rapidly during hyperpolarization and then rapidly inactivates. Iontophoretic injection of a Ca2+ chelator, EGTA, specifically reduces slow tail-current amplitude without affecting the fast tail component. Both K+ currents are inhibited by extracellular TEA+ in a concentration-dependent, noncooperative manner, whereas the fast K+ current alone is inhibited by 0.7 mM quinidine.

References

Jan 1, 1979·Annual Review of Biophysics and Bioengineering·R Eckert, P Brehm
Oct 19, 1978·The Journal of Membrane Biology·D OertelC Kung
Jan 1, 1987·Annual Review of Genetics·Y Saimi, C Kung
Jun 1, 1988·Neuroscience·B Rudy
Jun 1, 1984·The Journal of Physiology·R D Hinrichsen, Y Saimi
Jan 1, 1984·Annual Review of Physiology·B Sakmann, E Neher
Jan 1, 1982·Annual Review of Physiology·C Kung, Y Saimi
Aug 1, 1983·Proceedings of the National Academy of Sciences of the United States of America·Y SaimiC Kung

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Citations

Jun 1, 1990·BioEssays : News and Reviews in Molecular, Cellular and Developmental Biology·R R Preston
Sep 1, 1996·Pflügers Archiv : European journal of physiology·C K BauerJ R Schwarz
Dec 23, 1993·Biochimica Et Biophysica Acta·R D Hinrichsen
Dec 1, 1991·Proceedings of the National Academy of Sciences of the United States of America·J A KanabrockiC Kung
May 1, 1997·Photochemistry and Photobiology·F Saitow, Y Nakaoka
Aug 13, 2003·Eukaryotic Cell·W John HaynesChing Kung
Nov 30, 2012·The Journal of Eukaryotic Microbiology·Heidi K GrønlienOlav Sand
Jan 11, 2007·The Journal of Experimental Biology·Wade E BellJudith L Van Houten
Oct 12, 1990·Science·R R Preston

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