Abstract

Ca2+-activated K+ (KCa) channels of small (SK) and intermediate (IK) conductance are present in a wide range of excitable and non-excitable cells. On activation by low concentrations of Ca2+, they open, which results in hyperpolarization of the membrane potential and changes in cellular excitability. KCa-channel activation also counteracts further increases in intracellular Ca2+, thereby regulating the concentration of this ubiquitous intracellular messenger in space and time. KCa channels have various functions, including the regulation of neuronal firing properties, blood flow and cell proliferation. The cloning of SK and IK channels has prompted investigations into their gating, pharmacology and organization into calcium-signalling domains, and has provided a framework that can be used to correlate molecularly identified KCa channels with their native currents.