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Ligand gated ion channel

a transmembrane ion channel whose permeability is increased by the binding of a specific ligand, typically a neurotransmitter at a chemical synapse. The permeability change is often drastic, such channels let through effectively no ions when shut, but allow passage at up to 10exp7 ions sexp 1 when a ligand is bound. Recently, the receptors for both acetylcholine and gaba have been found to share considerable sequence homology, implying that there may be a family of structurally related ligand gated ion channels.