Pharmacological evidence for two types of Ca2+-dependent K+-conductance in bullfrog sympathetic ganglion cells

The effect of apamin, a bee venom toxin, on the action potential and the spike after hyperpolarization was studied in bullfrog sympathetic ganglion cells. Apamin reduced the duration of the afterhyperpolarization but did not affect the maximum rates of rise and fall of Na+- and Ca2+-dependent action potentials. In the presence of apamin and Co2+, the maximum rate of fall of the action potential was decreased, and the spike duration was prolonged. These results suggest that at least two types of Ca2+-dependent K+-conductance co-exist in bullfrog sympathetic ganglion cells.