Potassium channels are a diverse and ubiquitous family of membrane proteins present in both excitable and non-excitable cells. Members of this channel family play critical roles in cellular signaling processes regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume regulation. Over 50 human genes encoding various potassium channels have been cloned during the past decade. Based on the structure of the potassium channels, four main classes can be identified. The basis of all channels consists of four subunits that are clustered to form the ion-permeation pathway across the membrane. Each of the four subunits is build up of two transmembrane helices and a short loop between them. Distinct features characterize the four main classes: inwardly rectifying potassium channels (2TM/P channels), voltage and/or ligand gated ion channels (6TM/P channels), hybrid channels made from the two previously mentioned classes (8TM/2P channels), and dimer channels (4TM/2P channels) made from two repeats of the inwardly rectifying channels, and are often referred to as ‘leakage channels’. Also the hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels belong to the superfamily of voltage-gated K+ (Kv) and cyclic nucleotide-gated (CNG) channels. They are sometimes referred to as “pacemaker channels” because they help to generate rhythmic activity within groups of heart and brain cells.Axon Medchem offers a variety of potassium channel openers and blockers, including the racemate and optically pure enantiomers of BMS204352 (Axon 1112, Axon 1308, and Axon 1309), modulators of the Maxi-K channel (or BK channel, member of 6TM/P channel class), and Zatebradine HCl (Axon 1248, HCN channel blocker).