Electrical tuning and transduction in short hair cells of the chicken auditory papilla

Xiaodong Tan, Maryline Beurg, Carole Hackney, Shanthini Mahendrasingam, Robert Fettiplace*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The avian auditory papilla contains two classes of sensory receptor, tall hair cells (THCs) and short hair cells (SHCs), the latter analogous to mammalian outer hair cells with large efferent but sparse afferent innervation. Little is known about the tuning, transduction, or electrical properties of SHCs. To address this problem, we made patch-clamp recordings from hair cells in an isolated chicken basilar papilla preparation at 33°C. We found that SHCs are electrically tuned by a Ca2 -activated K current, their resonant frequency varying along the papilla in tandem with that of the THCs, which also exhibit electrical tuning. The tonotopic map for THCs was similar to maps previously described from auditory nerve fiber measurements. SHCs also possess an A-type K current, but electrical tuning was observed only at resting potentials positive to - 45 mV, where the A current is inactivated. We predict that the resting potential in vivo is approximately 40 mV, depolarized by a standing inward current through mechanotransducer (MT) channels having a resting open probability of 0.26. The resting open probability stems from a low endolymphatic Ca2 concentration (0.24 mM) and a high intracellular mobile Ca2 buffer concentration, estimated from perforated-patch recordings as equivalent to 0.5 mM BAPTA. The high buffer concentration was confirmed by quantifying parvalbumin-3 and calbindin D-28K with calibrated postembedding immunogold labeling, demonstrating 1 mM calcium-binding sites. Both proteins displayed an apex-to-base gradient matching that in the MT current amplitude, which increased exponentially along the papilla. Stereociliary bundles also labeled heavily with antibodies against the Ca2 pump isoform PMCA2a.

Original languageEnglish (US)
Pages (from-to)2007-2020
Number of pages14
JournalJournal of neurophysiology
Volume109
Issue number8
DOIs
StatePublished - 2013

Keywords

  • Calcium buffers
  • Chicken
  • Electrical tuning
  • Hair cells
  • Mechanotransduction

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

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