title: Mechanically and ATP-induced currents of mouse outer hair cells are independent and differentially blocked by d-tubocurarine.
abstract: Mechano-electrical transducer channels (MET) and ATP-gated ion channels (P2X receptors) of hair cells have several properties in common: they share the same location at the apex of the cell, both channels are non-selective for cations and blocked by aminoglycosides and pyrazinecarboxamides (amiloride-related compounds). In this study, we test the relationship and possible identity of these two channel types. Using whole-cell patch-clamp recordings of outer hair cells (OHCs) of the cultured neonatal mouse cochlea and a fluid jet to stimulate their hair bundles mechanically, we show that d-tubocurarine, a blocker of P2X2 receptors, blocks MET channels with a half-blocking concentration of 2.3 microM. In contrast, the KD for the P2X2 receptors was 90 microM and 84 microM measured in hair cells and Xenopus oocytes, respectively. When hair bundles of OHCs were simultaneously stimulated with saturating mechanical stimuli and superfused by 100-300 microM ATP, transducer currents and ATP-activated currents were elicited simultaneously. Their amplitudes were additive, however. We conclude that MET- and ATP-activated currents are mediated by two distinct channel populations in hair cells.
authors.affiliation: Department of Physiology, University of Tübingen, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Glowatzki
authors.forename: J P
authors.initials: JP
authors.lastname: Ruppersberg
authors.forename: H P
authors.initials: HP
authors.lastname: Zenner
authors.forename: A
authors.initials: A
authors.lastname: Rüsch
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D005260:Female; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D051379:Mice; D008813:Mice, Inbred ICR; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D018048:Receptors, Purinergic P2 / Q000502:physiology; D058476:Receptors, Purinergic P2X2; D014159:Transducers; D014403:Tubocurarine / Q000494:pharmacology*; D014981:Xenopus
chemical_list: D007473:Ion Channels; C546402:P2rx2 protein, mouse; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D000255:Adenosine Triphosphate; D014403:Tubocurarine