Voltage-gated K+ channels (Kv) determine the excitability of heart, brain and skeletal muscle cells. Kv form octameric channel with alpha subunits that forms the pore of the channel and associated beta subunits. The alpha subunits associate with beta subunits with a stoichiometry of alpha4beta4.The alpha subunits have been classified into 12 families, 1-12 with several representatives from each family. Members of Kv 1-4 form both homotetramers and heterotetramers, however, members of Kv 5-12 form functional heterotetramers. Kv's are expressed in the axon, at axon nodes, somatodendritic sites and axon termini.