Abstract
Isolated protoplasts from pulvinar motor cells of Mimosa pudica were studied using conventional whole-cell patch clamp techniques. With internal solutions weakly buffered for Ca2+ (0.2 mm EGTA), a run-down of the outward delayed rectifier K+ current was induced by hyperpolarizing the holding potential, and this effect was strongly promoted by high external Ca2+ concentrations. This rundown could be reversed by coming back to less hyperpolarized holding potentials or by lowering the external [Ca2+]. Such rundown was absent when pipette internal solutions strongly buffered (10 mm EGTA) for Ca2+ were used. Ionomycin induced run-down of the K+ current with internal solutions containing 0.2 mm but not 10 mm EGTA. The hyperpolarization-associated rundown was reversibly blocked by Gd3+ and La3+.
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We thank Christophe Untereiner and Denis Wagner for expert technical assistance in facilitating the experiments and data acquisition and analysis.
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Stoeckel, H., Takeda, K. Calcium-sensitivity of the plasmalemmal delayed rectifier potassium current suggests that calcium influx in pulvinar protoplasts from Mimosa pudica L. can be revealed by hyperpolarization. J. Membarin Biol. 146, 201–209 (1995). https://doi.org/10.1007/BF00238009
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DOI: https://doi.org/10.1007/BF00238009