(+)-Tubocurarine blocks the Ca2+-dependent K+-channel of the bullfrog sympathetic ganglion cell.

(+)-Tubocurarine [+)-Tc: 10-100 microM) reduced the duration of the afterhyperpolarization, which was induced by the activation of Ca2+-dependent K+-conductance (GK,Ca) following an action potential in the bullfrog sympathetic ganglion cell, but did not affect the maximum rates of rise and fall of Na+- and Ca2+-dependent action potentials. The amplitudes of slow rhythmic membrane hyperpolarizations produced by rhythmic rises in the GK,Ca were also decreased by (+)-Tc without a change in their intervals. Thus, (+)-Tc appears to block the Ca2+-dependent K+-channel of the bullfrog sympathetic ganglion cell.