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Publication Detail
FM1-43 dye behaves as a permeant blocker of the hair-cell mechanotransducer channel
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Journal Article
  • Authors:
    Gale JE, Marcotti W, Kennedy HJ, Kros CJ, Richardson GP
  • Publication date:
    15/09/2001
  • Pagination:
    7013, 7025
  • Journal:
    Journal of Neuroscience
  • Volume:
    21
  • Issue:
    18
  • Status:
    Published
  • Print ISSN:
    0270-6474
Abstract
Hair cells in mouse cochlear cultures are selectively labeled by brief exposure to FM1-43, a styryl dye used to study endocytosis and exocytosis. Real-time confocal microscopy indicates that dye entry is rapid and via the apical surface. Cooling to 4°C and high extracellular calcium both reduce dye loading. Pre-treatment with EGTA, a condition that breaks tip links and prevents mechanotransducer channel gating, abolishes subsequent dye loading in the presence of calcium. Dye loading recovers after calcium chelation with a time course similar to that described for tip-link regeneration. Myo7a mutant hair cells, which can transduce but have all mechanotransducer channels normally closed at rest, do not label with FM1-43 unless the bundles are stimulated by large excitatory stimuli. Extracellular perfusion of FM1-43 reversibly blocks mechanotransduction with half-blocking concentrations in the low micromolar range. The block is reduced by high extracellular calcium and is voltage dependent, decreasing at extreme positive and negative potentials, indicating that FM1-43 behaves as a permeant blocker of the mechanotransducer channel. The time course for the relief of block after voltage steps to extreme potentials further suggests that FM1-43 competes with other cations for binding sites within the pore of the channel. FM1-43 does not block the transducer channel from the intracellular side at concentrations that would cause complete block when applied extracellularly. Calcium chelation and FM1-43 both reduce the ototoxic effects of the aminoglycoside antibiotic neomycin sulfate, suggesting that FM1-43 and aminoglycosides enter hair cells via the same pathway.
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