Interleukin-lβ (IL-lβ) is a key proinflammatory cytokine.The increasing evidences have shown the effects of IL-1β on voltage-gated channels in neurons.The large-conductance Ca2+-activated K+ (BK) channel is widely distributed in various tissues and involved in many physiological functions.The chronic effects of IL-1β on BK channel and corresponding properties of action potential (AP) are not clear yet.Using patch-clamp recording in cultured cortical neurons, we found that IL-lβ did not change the unitary BK channel characteristics, but inhibited whole-cell BK current via reduction of Ca2+ currents.The current-clamp experiments showed that IL-1 β decreased the amplitude of fast after hyperpolarization (fAHP) through the inhibition of BK current.In contrast, the refractory period was 23% longer in IL-1β treated neurons.These data suggested the neuronal electrophysiological characteristics were modulated directly by IL-1β during insults to the brain.