Neuronal Currents (s) having The role of large-conductance Ca2+-dependent K+ channels (BK) in spike broadening during repetitive firing was studied using sharp electrode and computer modelling. The amplitude of the fast after-hyperpolarization (fAHP) rapidly declined during each train. Suppression of BK-channel activity with the selective BK-channel blocker iberiotoxin, the non-peptidergic BK-channel blocker paxilline, or calcium-free medium, broadened the 1st spike to a similar degree ( approximately 60 %) as Publication facts