Muscarinic acetylcholine receptor (subtypes M1, M2, M3, M4, M5) (mAChR (M1, M2, M3, M4, M5))

Muscarinic acetylcholine receptors (mAChRs) are a family of five G protein-coupled receptor subtypes (M1–M5) responsible for mediating the effects of the neurotransmitter acetylcholine in the central and peripheral nervous system[1][3][4]. Each subtype is encoded by distinct genes (CHRM1–CHRM5) and displays a specific tissue distribution and coupling to different G proteins: M1, M3, and M5 couple primarily to Gq proteins (excitatory; stimulate phospholipase C and increase intracellular calcium), while M2 and M4 couple to Gi/o proteins (inhibitory; decrease cAMP production)[1][4][5]. These receptors regulate numerous physiological functions including cognition, memory, cardiac rhythm, smooth muscle contraction, and glandular secretion[3][4][5]. mAChRs are major therapeutic targets for neurological, psychiatric, respiratory, and cardiovascular diseases, and both agonists and antagonists are used clinically depending on the subtype targeted. Recent advances in receptor structure have enabled the development of subtype-selective drugs, though the broad physiological roles of these receptors pose safety and specificity challenges for drug therapy[3][6].

Other names

Muscarinic receptormAChRAcetylcholine receptor M1–M5CHRM1–CHRM5

Antagonist/blockade (e.g., atropine blocks muscarinic receptors); Agonist/activation (e.g., pilocarpine stimulates muscarinic receptors); Allosteric modulation (e.g., selective allosteric modulators for M1, M5); Inverse agonism (tiotropium at M5)