LAUSR

Small-conductance Ca2+-activated K+ (SK) and large conductance, voltage- and Ca2+-activated K+ (BK) channels are Ca2+-activated K+ channels that control action potential firing diverse neurons in the brain. In cartwheel cells of the dorsal cochlear nucleus, blockade of either channel type leads to excessive production of spike bursts. In the same cells, P/Q-type Ca2+ channels in plasma membrane and ryanodine receptors in endoplasmic reticulum supply Ca2+ to BK channels through Ca2+ nanodomain signaling. In this study, voltage clamp experiments were performed in cartwheel cells in mouse brain slices in order to examine the Ca2+ signaling pathways underlying activation of SK channels. As with BK channels, SK channels required the activity of P/Q-type Ca2+ channels. However, this signaling occurred across Ca2+ micro- rather than nanodomain distances, and was independent of Ca2+ release from endoplasmic reticulum. These differential modes of activation may lead to distinct time courses of the two K+ currents and therefore control excitability of auditory neurons across different time scales.