Ca(2+) currents and voltage responses in Type I and Type II hair cells of the chick embryo semicircular canal

Pflugers Arch. 2005 Nov;451(2):395-408. doi: 10.1007/s00424-005-1466-7. Epub 2005 Aug 16.

Abstract

Type I and Type II hair cells, and Type II hair cells located in different zones of the semicircular canal crista, express different patterns of voltage-dependent K channels, each one specifically shaping the hair cell receptor potential. We report here that, close to hatching, chicken embryo semicircular canal Type I and Type II hair cells express a similar voltage-dependent L-type calcium current (I(Ca)), whose main features are: activation above -60 mV, fast activation kinetics, and scarce inactivation. I(Ca) should be already active at rest in Zone 1 Type II hair cells, whose resting membrane potential was on average slightly less negative than -60 mV. Conversely, I(Ca) would not be active at rest in Type II hair cells from Zone 2 and 3, nor in Type I hair cells, since their resting membrane potential was significantly more negative than -60 mV. However, even small depolarising currents would activate I(Ca) steadily in Zone 2 and 3 Type II hair cells, but not in Type I hair cells because of the robust repolarising action of their specific array of K(+) currents. The implications of the present findings in the afferent discharge are discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Barium / metabolism
  • Barium / pharmacology
  • Cadmium / pharmacology
  • Calcium / metabolism
  • Calcium / pharmacology
  • Calcium Channels, L-Type / physiology*
  • Cesium / pharmacology
  • Chick Embryo
  • Hair Cells, Vestibular / drug effects
  • Hair Cells, Vestibular / physiology*
  • Meglumine / pharmacology
  • Membrane Potentials / drug effects
  • Nickel / pharmacology
  • Semicircular Canals / cytology
  • Semicircular Canals / drug effects
  • Semicircular Canals / physiology*

Substances

  • Calcium Channels, L-Type
  • Cadmium
  • Cesium
  • Barium
  • Meglumine
  • Nickel
  • Calcium