Tests of whole-cell inactivating BK current in mouse CCs. (A) The indicated voltage protocol was used to elicit current during perforated patch recordings. As the duration of a loading step to 10 mV is increased, peak outward current during the step to 80 mV is progressively reduced and current decays almost completely to a level identical to that evoked by voltage alone. This defines a cell with largely inactivating BK current. (B) In another dissociated mouse CC, increases in the loading step duration result in increasingly diminished current decay during the step to 80 mV. This reflects largely noninactivating BK current (right). The red traces highlight the direct step to 80 mV from −120 mV, reflecting primarily Kv current. (C) Traces show currents from a mouse CC from adrenal medullary slices with inactivating BK current. For cells in slices, the positive test step was to 110 mV. (D) Traces show a mouse CC in a slice with largely noninactivating BK current. (E) Traces show a rat CC in a slice with largely inactivating BK current. (F) Traces highlight a mostly noninactivating BK current in a rat CC from a slice. (G) Traces from a slo1 KO CC illustrate the absence of a current dependent on a Ca²⁺ loading step.