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J Membr Biol. 1995 Jul;146(2):201-9.

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.

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Institut de Biologie Mol├ęculaire des Plantes-CNRS UPR406, Strasbourg, France.


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 rundown 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 rundown 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+.

[Indexed for MEDLINE]

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