Localization of inner hair cell mechanotransducer channels using high-speed calcium imaging

Nat Neurosci. 2009 May;12(5):553-8. doi: 10.1038/nn.2295. Epub 2009 Mar 29.


Hair cells detect vibrations of their stereociliary bundle by activation of mechanically sensitive transducer channels. Although evidence suggests the transducer channels are near the stereociliary tops and are opened by force imparted by tip links connecting contiguous stereocilia, the exact channel site remains controversial. We used fast confocal imaging of fluorescence changes reflecting calcium entry during bundle stimulation to localize the channels. Calcium signals were visible in single stereocilia of rat cochlear inner hair cells and were up to tenfold larger and faster in the second and third stereociliary rows than in the tallest first row. The number of functional stereocilia was proportional to transducer current amplitude, indicating that there were about two channels per stereocilium. Comparable results were obtained in outer hair cells. The observations, supported by theoretical simulations, suggest there are no functional mechanically sensitive transducer channels in first row stereocilia and imply the channels are present only at the bottom of the tip links.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Calcium Channels / physiology*
  • Calcium Channels / ultrastructure
  • Calcium Signaling / physiology
  • Cell Size
  • Cilia / physiology*
  • Cilia / ultrastructure
  • Fluorescent Dyes
  • Hair Cells, Auditory, Inner / physiology*
  • Hair Cells, Auditory, Inner / ultrastructure
  • Hearing / physiology
  • Mechanotransduction, Cellular / physiology*
  • Microscopy, Confocal / methods
  • Neurophysiology / methods
  • Organ of Corti / physiology*
  • Organ of Corti / ultrastructure
  • Rats
  • Rats, Sprague-Dawley
  • Staining and Labeling / methods
  • Time Factors


  • Calcium Channels
  • Fluorescent Dyes