Abstract
The whole-cell patch-clamp technique was applied to rat choroid plexus epithelial cells. The resting membrane potential was −53 mV. The whole-cell conductance was mainly K+ selective, and the K+ current observed appeared to contain two distinct components. Depolarizing voltage pulses (more positive than 0 mV) evoked time-dependent outward currents which resembled delayed-rectifying K+ currents in other tissues. The current exhibited time-dependent activation and, at potentials more positive than 40 mV, slower time-dependent inactivation. The reversal potential measured by tail current analysis showed a shift of 43 mV for a tenfold increase in extracellular K+ concentration ([K+]0). The current was reduced by extracellular 5 mM Ba2+, 5 mM tetraethylammonium (TEA+), 5 mM Cs+ and 1 mM 4-aminopyridine (4-AP). In contrast, hyperpolarizing voltage pulses evoked time-independent, inward-rectifying currents. The reversal potential measured by voltageramp commands showed a shift of 42 mV for a tenfold increase in [K+]0. The chord conductance did not appear to increase with increasing [K+]0. The current was reduced by extracellular 5 mM Ba2+ and 0.5 mM Cs+, but not by 5 mM TEA+ or 1 mM 4-AP. These data suggest that two populations of K+ channel contribute to the conductance of choroid plexus epithelial cells.
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Kotera, T., Brown, P.D. Evidence for two types of potassium current in rat choroid plexus epithelial cells. Pflügers Arch 427, 317–324 (1994). https://doi.org/10.1007/BF00374540
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DOI: https://doi.org/10.1007/BF00374540