title: Differences between the negatively activating potassium conductances of Mammalian cochlear and vestibular hair cells.
abstract: Cochlear and type I vestibular hair cells of mammals express negatively activating potassium (K(+)) conductances, called g(K,n) and g(K,L) respectively, which are important in setting the hair cells' resting potentials and input conductances. It has been suggested that the channels underlying both conductances include KCNQ4 subunits from the KCNQ family of K(+) channels. In whole-cell recordings from rat hair cells, we found substantial differences between g(K,n) and g(K,L) in voltage dependence, kinetics, ionic permeability, and stability during whole-cell recording. Relative to g(K,L), g(K,n) had a significantly broader and more negative voltage range of activation and activated with less delay and faster principal time constants over the negative part of the activation range. Deactivation of g(K,n) had an unusual sigmoidal time course, while g(K,L) deactivated with a double-exponential decay. g(K,L), but not g(K,n), had appreciable permeability to Cs(+). Unlike g(K,L), g(K,n)'s properties did not change ("wash out") during the replacement of cytoplasmic solution with pipette solution during ruptured-patch recordings. These differences in the functional expression of g(K,n) and g(K,L) channels suggest that there are substantial differences in their molecular structure as well.
authors.affiliation: The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
authors.forename: Weng Hoe
authors.initials: WH
authors.lastname: Wong
authors.forename: Karen M
authors.initials: KM
authors.lastname: Hurley
authors.forename: Ruth Anne
authors.initials: RA
authors.lastname: Eatock
mesh_terms: D000818:Animals; D002586:Cesium / Q000493:pharmacokinetics; D003051:Cochlea / Q000166:cytology / Q000502:physiology; D006199:Hair Cells, Auditory, Inner / Q000502:physiology*; D018069:Hair Cells, Vestibular / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology; D007700:Kinetics; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D051381:Rats; D014722:Vestibule, Labyrinth / Q000166:cytology / Q000502:physiology
chemical_list: D015221:Potassium Channels; D002586:Cesium; D011188:Potassium