Abstract
Vestibular type II hair cells respond to increases in the hydrostatic pressure with pressure-dependent K+ currents. We examined whether such currents may modulate transmitter release (assessed as membrane capacitance increments) by altering membrane potentials and voltage-gated Ca2+ currents. Capacitance increments were dependent on voltage-gated Ca2+ influx. Stimulating currents (0.7 nA) in current clamp induced depolarisations that were more negative by 8.7 ± 2.1 mV when the bath height was elevated from 0.2 to 0.5 cm. In voltage clamp, protocols were used that simulated the time course of the membrane potential in current clamp at either low (control) or high hydrostatic pressure (high bath). The low bath protocol induced significantly larger Ca2+ currents and increases in capacitance than the high bath protocol. We conclude that pressure-dependent K+ currents may alter the voltage response of vestibular hair cells to an extent critical for Ca2+ currents and transmitter release. This mechanism may contribute to vestibular dysfunction in Meniere’s disease.
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Acknowledgements
The study was supported by a grant of Hennig Pharmazeuticals, Flörsheim am Main, Germany, to T.D. and a START grant by the Medical Faculty Aachen to T.H.
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Duong Dinh and Haasler contributed equally to this work.
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Supplementary Fig. 1
K+ currents in a vestibular type II hair cell induced by hydrostatic pressure. K+ outward currents were elicited by a depolarising pulse to 0 mV for 20 ms. The height of the bath was 0.5 cm during trace 1, then lowered to 0.2 cm for trace 2 and put back to 0.5 cm for trace 3 (GIF 24.0 kb)
Supplementary Fig. 2
Ca2+ currents (measured with 20 mM Ba2+ as charge carrier) during low and high hydrostatic pressure. The upper panel shows two superposed current traces during depolarisations tow −10 mV. The lower panel shows current values at various command voltages (GIF 28.8 kb)
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Duong Dinh, T.A., Haasler, T., Homann, G. et al. Potassium currents induced by hydrostatic pressure modulate membrane potential and transmitter release in vestibular type II hair cells. Pflugers Arch - Eur J Physiol 458, 379–387 (2009). https://doi.org/10.1007/s00424-008-0622-2
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DOI: https://doi.org/10.1007/s00424-008-0622-2