Effects of Cationic Substitutions on Delayed Rectifier Current in Type I Vestibular Hair Cells |
| |
Authors: | KJ Rennie MJ Correia |
| |
Institution: | (1) Department of Otolaryngology, The University of Texas Medical Branch, Galveston, Texas 77555, USA, US;(2) Department of Physiology and Biophysics, The University of Texas Medical Branch, Galveston, Texas 77555, USA, US |
| |
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+.
Received: 23 June 1999/Revised: 27 September 1999 |
| |
Keywords: | : Semicircular canal — Utricle — Gerbil — Potassium channel — Anomalous mole fraction |
本文献已被 PubMed SpringerLink 等数据库收录! |
|