Ion channels as targets for treatment of gastrointestinal motility disorders.

Ion channels are found in every cell type. Ion channels are membrane proteins that allow regulated transfer of ions across the membrane. As a result, they often produce electrical signals that regulate cellular function and transduce signals into electrical events. Ion channels can be broadly classified into voltage-gated ion channels, ligand-gated ion channels and mechanosensitive ion channels according to their primary gating modality. Most ion channel gating is regulated by more that one mechanism, and therefore there is considerable overlap between the three classes. Due to the highly regulated nature of the opening and closing of most ion channels and the number of small molecules that have been shown to both activate (open) and inhibit (close or inactivate) ion channels, ion channels are often considered as attractive targets for drugs. There are over 400 ion channel genes representing over 1.5% of the human genome, yet less than 10 ion channels are currently the target of available drugs. This presents a potential opportunity. Classes of ion channels expressed in the gastrointestinal tract that are known targets for drugs include: