Abstract.
The resting potassium current (I KI ) in gerbil dissociated type I vestibular hair cells has been characterized under various ionic conditions in whole cell voltage-clamp. When all K+ in the patch electrode solution was replaced with Na+, (Na+) in or Cs+, (Cs+) in , large inward currents were evoked in response to voltage steps between −90 and −50 mV. Activation of these currents could be described by a Hodgkin-Huxley-type kinetic scheme, the order of best fit increasing with depolarization. Above ∼−40 mV currents became outward and inactivated with a monoexponential time course. Membrane resistance was inversely correlated with external K+ concentration. With (Na+) in , currents were eliminated when K+ was removed from the external solution or following extracellular perfusion of 4-aminopyridine, indicating that currents flowed through I KI channels. Also, reduction of K+ entry through manipulation of membrane potential reduced the magnitude of the outward current. Under symmetrical Cs+, 0 K+ conditions I KI is highly permeable to Cs+. However, inward currents were reduced when small amounts of external K+ were added. Higher concentrations of K+ resulted in larger currents indicating an anomalous mole fraction effect in mixtures of external Cs+ and K+.
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Received: 23 June 1999/Revised: 27 September 1999
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Rennie, K., Correia, M. Effects of Cationic Substitutions on Delayed Rectifier Current in Type I Vestibular Hair Cells. J. Membrane Biol. 173, 139–148 (2000). https://doi.org/10.1007/s002320001015
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DOI: https://doi.org/10.1007/s002320001015