Adrenaline-induced K+ efflux results in sodium pump stimulation in a sympathetic ganglion

The potassium-activated hyperpolarization (KH) was used as an index of electrogenic Na+ pumping in bullfrog sympathetic ganglia. This response was evoked by storing ganglia in K-free Ringer's solution and briefly introducing normal Ringer's solution containing 2 mM K+ at regular intervals. The apparent EC50 for K+ was 2.21 mM (range 0.88-3.54 mM, for n = 5) and at least 10 mM K+ was required to produce a maximal KH response. Adrenaline, which produces membrane hyperpolarization by increasing K+ conductance (gK), increased the amplitude of KH responses. When the K+ efflux accompanying the adrenaline-induced hyperpolarization (AdH) was blocked with 2 mM Ba2+, the KH was no longer potentiated. It is suggested that the K+ moving out of the cells during the AdH accumulates extracellularly and stimulates the Na+ pump.