Evidence for two types of potassium current in rat choroid plexus epithelial cells.
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+]o). 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 voltage-ramp commands showed a shift of 42 mV for a tenfold increase in [K+]o. The chord conductance did not appear to increase with increasing [K+]o. 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.
Kotera
T
T
Department of Physiological Sciences, University of Manchester, UK.
Brown
P D
PD
D000818:Animals; D002831:Choroid Plexus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D016623:Ion Pumps / Q000502:physiology; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D016623:Ion Pumps; D015221:Potassium Channels; D011188:Potassium