Apamin-sensitive, small-conductance, calcium-activated potassium channels mediate cholinergic inhibition of chick auditory hair cells

W. A. Yuhas, Paul Albert Fuchs

Research output: Contribution to journalArticle


Acetylcholine released from efferent neurons in the cochlea causes inhibition of mechanosensory hair cells due to the activation of calcium-dependent potassium channels. Hair cells are known to have large-conductance, 'BK'-type potassium channels associated with the afferent synapse, but these channels have different properties than those activated by acetylcholine. Whole-cell (tight-seal) and cell-attached patch-clamp recordings were made from short (outer) hair cells isolated from the chicken basilar papilla (cochlea equivalent). The peptides apamin and charybdotoxin were used to distinguish the calcium-activated potassium channels involved in the acetylcholine response from the BK-type channels associated with the afferent synapse. Differential toxin blockade of these potassium currents provides definitive evidence that ACh activates apamin-sensitive, 'SK'-type potassium channels, but does not activate carybdotoxin-sensitive BK channels. This conclusion is supported by tentative identification of small-conductance, calcium-sensitive but voltage-insensitive potassium channels in cell-attached patches. The distinction between these channel types is important for understanding the segregation of opposing afferent and efferent synaptic activity in the hair cell, both of which depend on calcium influx. These different calcium-activated potassium channels serve as sensitive indicators for functionally significant calcium influx in the hair cell.

Original languageEnglish (US)
Pages (from-to)455-462
Number of pages8
JournalJournal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology
Issue number5
Publication statusPublished - Nov 1999



  • Apamin
  • BK
  • Charybdotoxin
  • Cochlea
  • SK

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Physiology
  • Physiology (medical)
  • Behavioral Neuroscience
  • Neuroscience(all)

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