Nicotinic Receptor Type — FRCA Primary MCQ
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Correct answer: D — Ligand-gated ion channel
The nicotinic acetylcholine receptor is a pentameric ligand-gated ion channel. Acetylcholine binding produces a conformational change that opens its central cation-selective pore. At the neuromuscular junction, inward Na+ movement predominates over outward K+ movement at the resting membrane potential, producing rapid end-plate depolarisation. It is therefore an ionotropic receptor. Muscarinic acetylcholine receptors, by contrast, are G-protein-coupled receptors. Voltage-gated channels open in response to changes in membrane potential rather than direct agonist binding. Receptor tyrosine kinases, such as the insulin receptor, signal through phosphorylation, while intracellular receptors mediate the actions of lipid-soluble ligands such as steroid hormones.
Reference: Cecchini M, Corringer PJ, Changeux JP. The Nicotinic Acetylcholine Receptor and Its Pentameric Homologs: Toward an Allosteric Mechanism of Signal Transduction at the Atomic Level. Annual Review of Biochemistry. 2024;93:339-366. https://pubmed.ncbi.nlm.nih.gov/23038257/