Ca2+-dependent kinetics of hair cell Ca2+ currents resolved with the use of cesium BAPTA.
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.
Rispoli
G
G
INFM, Dipartimento di Biologia, Università di Ferrara, Italy.
Martini
M
M
Rossi
M L
ML
Rubbini
G
G
Fesce
R
R
D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002586:Cesium / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology*; D003593:Cytoplasm / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*; D004553:Electric Conductivity; D006198:Hair Cells, Auditory / Q000502:physiology*; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D008954:Models, Biological; D011188:Potassium / Q000494:pharmacology; D011893:Rana esculenta
D015220:Calcium Channels; D002614:Chelating Agents; D002586:Cesium; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D011188:Potassium; D002118:Calcium