Olivocochlear suppression of outer hair cells in vivo: evidence for combined action of BK and SK2 channels throughout the cochlea

J Neurophysiol. 2013 Mar;109(6):1525-34. doi: 10.1152/jn.00924.2012. Epub 2013 Jan 2.


Cholinergic inhibition of cochlear hair cells via olivocochlear (OC)-efferent feedback is mediated by Ca(2+) entry through α9-/α10-nicotinic receptors, but the nature of the K(+) channels activated by this Ca(2+) entry has been debated (Yoshida N, Hequembourg SJ, Atencio CA, Rosowski JJ, Liberman MC. J Neurophysiol 85: 84-88, 2001). A recent in vitro study (Wersinger E, McLean WJ, Fuchs PA, Pyott SJ. PLoS One 5: e13836, 2010) suggests that small-conductance (SK2) channels mediate cholinergic effects in the apical turn, whereas large-conductance (BK) channels mediate basal turn effects. Here, we measure, as a function of cochlear frequency, the magnitude of BK and SK2 expression in outer hair cells and the strength of in vivo OC suppression in BK(+/+) mice vs. BK(-/-) lacking the obligatory α-subunit (Meredith AL, Thorneloe KS, Werner ME, Nelson MT, Aldrich RW. J Biol Chem 279: 36746-36752, 2004). Except at the extreme apical tip, we see immunostaining for both BK and SK2 in BK(+/+). Correspondingly, at all testable frequencies (8-45 kHz), we see evidence for both SK2 and BK contributions to OC effects evoked by electrically stimulating the OC bundle: OC-mediated suppression was reduced, but not eliminated, at all frequencies in the BK(-/-) ears. The suppression remaining in BK nulls was blocked by strychnine, suggesting involvement of α9-/α10-cholinergic receptors, coupled to activation of the remaining SK2 channels.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Auditory Pathways / drug effects
  • Auditory Pathways / metabolism*
  • Auditory Pathways / physiology
  • Cochlea / cytology
  • Cochlea / physiology
  • Hair Cells, Auditory, Outer / metabolism
  • Hair Cells, Auditory, Outer / physiology*
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / genetics
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / metabolism*
  • Mice
  • Mice, Mutant Strains
  • Small-Conductance Calcium-Activated Potassium Channels / genetics
  • Small-Conductance Calcium-Activated Potassium Channels / metabolism*
  • Strychnine / pharmacology


  • Kcnn2 protein, mouse
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
  • Small-Conductance Calcium-Activated Potassium Channels
  • Strychnine