Ca super(2+)-dependent kinetics of hair cell Ca super(2+) currents resolved with the use of cesium BAPTA

Hair cells in the frog semicircular canal, studied by the wholecell patch-clamp technique, display three distinct Ca super(2+) 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 Ca super(2+)-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 [Ca super(2+)] sub(i) more efficiently and investigate whether modifications in [Ca super(2+)] sub(i) at the cytoplasmic side of the channel affect the inactivation of the R1 component and in general the gating of all channel types. The results here reported show that (1) K super(+) currents heavily contaminate recordings obtained using high concentrations of BAPTA in its commercially available K super(+) salt form; (2) BAPTA Cs super(+) 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 [Ca super(2+)] sub(i).