Absence of β2 subunits reduces frequency of APs evoked by constant current injection and predisposes to burst firing. (A) AP firing was elicited by either a 5 (left)- or 20-pA (middle) constant current pulse in a CC with BK_i current (confirmed with the protocol and traces on right). (B) AP firing was elicited in a BK_s cell (sample traces on right) with either 5- or 20-pA current pulses. (C) Two examples of CCs in adrenal slices from β2 KO mice are shown both with 5 (left)- and 20-pA (right) current injection. Note the slow-wave activity with bursts of spikes at 5 pA. (D) A slo1 KO CC is displayed for 5- and 20-pA current injections. (E) The mean (±SD) number of evoked APs (excursions above 0 mV) is plotted as a function of injected current amplitude for the four cell types.