title: Potassium currents in vestibular type II hair cells activated by hydrostatic pressure.
abstract: An elevated hydrostatic pressure in the endolymphatic space of the inner ear is discussed as pathophysiological factor in hydrops-related diseases of the inner ear. An increase in pressure by fractions of 1 cm H(2)O is sufficient to induce vertigo-like symptoms in animal models. To establish a link between hydrostatic pressure and the function of vestibular hair cells, we studied potassium currents in isolated vestibular type II hair cells from guinea-pig utricles when the hydrostatic pressure was increased by raising the height of the bath from 0.2-0.5, 0.7 or 1.0 cm. Elevated pressure enhanced K(+) currents significantly; a rise in pressure from 0.2-0.5 cm H(2)O increased the total K(+) current at +40 mV by 22+/-14% (+/-S.D.). The pressure-sensitive current I(K,p) was non-inactivating during depolarizing pulses. It was maintained when the pressure was kept elevated for several minutes and receded promptly after return to a pressure of 0.2 cm H(2)O. Voltage-gated Ca(2+) currents, in contrast, were not altered by hydrostatic pressure. A pharmacological characterization of I(K,p) revealed that tetraetylammonium (100 mM) abolished all outward currents including I(K,p). I(K,p) was partly and reversibly inhibited by 4-aminopyridine. Dihydrostreptomycin, a blocker of the transduction channel, left I(K,p) unaffected. Charybdotoxin (100 nM), a blocker of Ca(2+)-dependent K(+) channels, completely yet reversibly abolished I(K,p). We conclude that small elevations in hydrostatic pressure evoke a charybdotoxin-sensitive, probably Ca(2+)-dependent K(+) current in vestibular hair cells. This is likely to alter their frequency response and may be a relevant mechanism how hydrostatic pressure disturbs transduction.
authors.affiliation: Institute of Physiology, University Hospital RWTH, Aachen, Germany. pduewel@ukaachen.de
authors.forename: P
authors.initials: P
authors.lastname: Düwel
authors.forename: E
authors.initials: E
authors.lastname: Jüngling
authors.forename: M
authors.initials: M
authors.lastname: Westhofen
authors.forename: A
authors.initials: A
authors.lastname: Lückhoff
mesh_terms: D000818:Animals; D006168:Guinea Pigs; D018069:Hair Cells, Vestibular / Q000378:metabolism*; D006874:Hydrostatic Pressure / Q000009:adverse effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D015221:Potassium Channels / Q000378:metabolism*
chemical_list: D015221:Potassium Channels