Current Oscillations Under Voltage-Clamp Conditions: An Interplay of Series Resistance and Negative Slope Conductance

Current Oscillations Under Voltage-Clamp Conditions: An Interplay of Series Resistance and... Using the patch-clamp technique, we observed profound oscillations of the whole-vacuole outward current across the tonoplast of Mesembryanthemum crystallinum L. (common ice plant). These current oscillations showed a clear voltage dependence and appeared at membrane potentials more positive than 90–100 mV. This paper describes the oscillations in terms of two separate mechanisms. First, the Mesembryanthemum vacuolar membrane shows a negative slope conductance at membrane potentials more positive than 100–120 mV. The fact that the oscillations and the negative slope conductance show a similar threshold potential suggests that (part of) the same mechanism is involved in both phenomena. The second mechanism involved is the voltage drop across the series resistance. As a result, the potential actually experienced by the vacuolar membrane deviates from the command potential defined by the patch-clamp amplifier. This deviation depends in an Ohmic manner on the current magnitude. We suggest that the interplay of the negative slope conductance and the voltage drop across the series resistance can cause a positive feedback which is responsible for the current oscillations. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Current Oscillations Under Voltage-Clamp Conditions: An Interplay of Series Resistance and Negative Slope Conductance

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2000 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002320001004
Publisher site
See Article on Publisher Site

Abstract

Using the patch-clamp technique, we observed profound oscillations of the whole-vacuole outward current across the tonoplast of Mesembryanthemum crystallinum L. (common ice plant). These current oscillations showed a clear voltage dependence and appeared at membrane potentials more positive than 90–100 mV. This paper describes the oscillations in terms of two separate mechanisms. First, the Mesembryanthemum vacuolar membrane shows a negative slope conductance at membrane potentials more positive than 100–120 mV. The fact that the oscillations and the negative slope conductance show a similar threshold potential suggests that (part of) the same mechanism is involved in both phenomena. The second mechanism involved is the voltage drop across the series resistance. As a result, the potential actually experienced by the vacuolar membrane deviates from the command potential defined by the patch-clamp amplifier. This deviation depends in an Ohmic manner on the current magnitude. We suggest that the interplay of the negative slope conductance and the voltage drop across the series resistance can cause a positive feedback which is responsible for the current oscillations.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 1, 2000

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