title: Adaptation of mammalian auditory hair cell mechanotransduction is independent of calcium entry.
abstract: Adaptation is a hallmark of hair cell mechanotransduction, extending the sensory hair bundle dynamic range while providing mechanical filtering of incoming sound. In hair cells responsive to low frequencies, two distinct adaptation mechanisms exist, a fast component of debatable origin and a slow myosin-based component. It is generally believed that Ca(2+) entry through mechano-electric transducer channels is required for both forms of adaptation. This study investigates the calcium dependence of adaptation in the mammalian auditory system. Recordings from rat cochlear hair cells demonstrate that altering Ca(2+) entry or internal Ca(2+) buffering has little effect on either adaptation kinetics or steady-state adaptation responses. Two additional findings include a voltage-dependent process and an extracellular Ca(2+) binding site, both modulating the resting open probability independent of adaptation. These data suggest that slow motor adaptation is negligible in mammalian auditory cells and that the remaining adaptation process is independent of calcium entry.
authors.affiliation: Department of Otolaryngology, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Peng
authors.forename: Thomas
authors.initials: T
authors.lastname: Effertz
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Ricci
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000465:Algorithms; D000818:Animals; D016477:Artifacts; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D055724:Electrophysiological Phenomena; D006199:Hair Cells, Auditory, Inner / Q000378:metabolism / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008810:Mice, Inbred C57BL; D009925:Organ of Corti / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002118:Calcium