Calcium currents recorded from a neuronal α1C L‐type calcium channel in Xenopus oocytes

Abstract

Xenopus oocytes expressing neuronal α_1C, α₂ and β_1b calcium channel subunit cDNAs were used in this study. During two-electric voltage clamp recording the oocyte was injected with 10–20 nl of a 100 mM BAPTA solution. Under these conditions, the endogenous Ca-activated Cl current was completely suppressed resulting in an α_1C Ba current free from Cl current contamination. BAPTA injection also allowed α_1C currents with different permeating ions, including Ca, to be examined. Compared to Ba and Sr, α_1C whole cell Ca currents were smaller in magnitude and showed kinetic and voltage-dependent properties more similar to those for L-type Ca currents recorded in native cells. That Ca-dependent inactivation occurs in BAPTA-buffered cells suggests that the Ca-binding site involved in this type of inactivation is very close to the pore of the channel.