Abstract
Electrophysiological states of the marine diatom Coscinodiscus wailesii are known to change spontaneously in the temporal range of seconds. In order to assess the genuine current-voltage-time relationships of individual states in less than a second, voltage-clamp experiments have been carried out using single sweeps of saw-tooth shaped command voltages. This method is introduced with model calculations. Plotting the results in current-voltage coordinates provides convenient access to several electrophysiological entities, such as absence of drift (smoothly closed IV loops), membrane capacitance (by I jump at sign reversal of dV/dt), and ohmic conductances (in linear regions of the current-voltage relationship), as well as equilibrium voltage (internal intersection of capacitance-corrected, 8-shaped tracings) and coarse gating kinetics (rise or fall of capacitance-corrected I at sign reversal of dV/dt) of a voltage-sensitive ion conductance. From electrophysiological measurements with double-barreled glass-microelectrodes on C. wailesii, several distinct types of current-voltage loops are presented. Most of the data, including recordings from electrical excitation, can be interpreted as temporal relaxations of voltage-sensitive conductances for K+ and Cl−. A more detailed analysis of the effect of tetraethylammonium (TEA+) shows that 10 and 20 mM TEA+ inhibit the K+ conductance in C. wailesii only by up to about 20% but predominantly via a K+ outward rectifier.
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Received: 23 December 1998 / Revised version: 1 June 1999 / Accepted: 1 June 1999
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Gradmann, D., Boyd, C. Electrophysiology of the marine diatom Coscinodiscus wailesii IV: types of non-linear current-voltage-time relationships recorded with single saw-tooth voltage-clamp experiments. Eur Biophys J 28, 591–599 (1999). https://doi.org/10.1007/s002490050241
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DOI: https://doi.org/10.1007/s002490050241