A major role for calcium-dependent potassium current in action potential repolarization in adrenal chromaffin cells

Abstract

To determine the extent which Ca dependent K current (I KCa) contributes during an action potential (AP), bovine chromaffin cells were voltage-clamped using a pre-recorded AP as the command voltage waveform. Based on (1) differential sensitivity of I KCa and Ca-independent K current ( I K ) to tetraethylammonium; (2) measurements of AP currents under conditions where Ca activation of I KCa had been abolished; and (3) blockade by charybdotoxin, I KCa comprised 70–90% of the outward K current during AP repolarization. In addition, observations are made concerning the form of AP-evoked Ca current.