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Ligand-gated ion channels are transmembrane proteins that open in response to a chemical messenger like a neurotransmitter, ion, or nucleotide, generally called a ligand.

These channels contain a receptor domain for the ligand to bind and a transmembrane pore for the ions to pass through.

Generally, the channel remains closed when the receptor is not bound by any ligand. As soon as a ligand binds to the receptor, the protein undergoes a conformational change, opening the channels' pore that allows the ions to pass through.

As the ligand dissociates, the channel closes, preventing the ions' movement. Note that the ligand itself is never transported across the membrane.

Ligands can be extracellular like acetylcholine and glutamate; or intracellular like cyclic adenosine monophosphate, and ions like calcium.

These channels are critical for communication between neurons. For example, the neurotransmitter glutamate released in the synaptic cleft stimulates neighboring neurons by binding to their glutamate-specific receptors, causing the channels to open. The resulting influx of sodium ions generates action potential in the target cell.