(+)-Tubocurarine is a potent inhibitor of cation channels in the vacuolar membrane of Chenopodium rubrum L.

The effect of the acetylcholine antagonist and channel blocker (+)-tubocurarine on the calcium-dependent slow vacuolar (SV) cation channels in the tonoplast of suspension-cultured cells of Chenopodium rubrum L. was examined using the patch-clamp technique. In whole-vacuolar recordings the drug strongly suppressed the potassium conductance (EC50: 6 microM) and altered the kinetics of channel inactivation. In excised membrane patches (+)-tubocurarine evokes channel-'flickering' without affecting the single-channel conductance (approx. 80 pS).