(cell and molecular biology) A receptor in the membranes of certain cell structures, such as synapses or the neuromuscular junction, to which the transmitter substance acetylcholine binds. Nicotinic acetylcholine receptors are gated ion channels that open in response to acetylcholine, leading to an increase in membrane conductance; muscarinic acetylcholine receptors are G-protein-linked receptors inducing membrane ion channel changes or intracellular processes such as smooth muscle contraction.

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