β2 KO CCs are more likely to exhibit burst firing. (A) Frequency distribution among three firing behaviors are plotted for BK_i (n = 12 cells, left), BK_s (n = 19 cells, middle-left), β2 KO (n = 23 cells, middle-right), and slo1 KO (n = 15 cells, right). Spontaneous activity was typically evaluated for a period of 150 s. Firing categories were as follows: 1, APs at a total frequency of <0.2 Hz (this includes quiescent cells in which APs could be evoked by depolarization); 2, repetitively firing APs at a frequency of >0.2 Hz; and 3, repetitive firing in which full-size APs precipitated burst firing. (B) AP firing frequency for BK_i, BK_s, β2 KO, and slo1 KO cells. Cells firing at <0.2 Hz were not included. For β2 KO cells, each burst was considered as a single event. Error bars indicate SEM.