Résumé
We previously reported that the opening of the L-type Ca
2+ channel was only partly involved in the K
+-evoked Ca
2+-dependent γ-aminobutyric acid (GABA) release from striatal neurons, suggesting that probably different types of voltage-sensitive Ca
2+ channels were implicated in this physiological process. Here we demonstrate that ω-contoxin GVIA, which has been reported to block L- and N-type neuronal Ca
2+ channels, also partly inhibits the Ca
2+-dependent GABA release. The maximal effects of ω-conotoxin GVIA and nifedipine, a highly specific antagonist of the L-type channels, were additive, a total inhibition of the Ca
2+-dependent GABA release being obtained in the presence of both drugs. We therefore propose that ω-conotoxin GVIA and nifedipine block two different types of Ca
2+ channels, both involved in the GABA release process.