Ca2+-dependent kinetics of hair cell Ca2+ currents resolved with the use of cesium BAPTA

Neuroreport. 2000 Aug 21;11(12):2769-74. doi: 10.1097/00001756-200008210-00032.

Abstract

Hair cells in the frog semicircular canal, studied by the whole-cell patch-clamp technique, display three distinct Ca2+ currents: two non-inactivating components (L type and R type, the latter termed R2 in the following) and a second R type current (termed R1), which runs down first and inactivates in a Ca2+-dependent fashion. Since intracellular EGTA, up to 5 mM, did not display major effects on such inactivation, we used increasing amounts of BAPTA in the patch pipette, to control [Ca2+]i more efficiently and investigate whether modifications in [Ca2+]i at the cytoplasmic side of the channel affect the inactivation of the RI component and in general the gating of all channel types. The results here reported show that (1) K+ currents heavily contaminate recordings obtained using high concentrations of BAPTA in its commercially available K+ salt form; (2) BAPTA Cs+ salt can be satisfactorily employed to obtain reliable recordings; (3) the kinetics of channel gating and R1-channel inactivation are indeed markedly affected by effectively buffering [Ca2+]i.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / physiology*
  • Calcium Channels / drug effects
  • Calcium Channels / physiology*
  • Cesium / pharmacology
  • Chelating Agents / pharmacology*
  • Cytoplasm / metabolism
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology*
  • Electric Conductivity
  • Hair Cells, Auditory / physiology*
  • Ion Channel Gating / drug effects
  • Kinetics
  • Models, Biological
  • Potassium / pharmacology
  • Rana esculenta

Substances

  • Calcium Channels
  • Chelating Agents
  • Cesium
  • Egtazic Acid
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Potassium
  • Calcium