Muscarinic acetylcholine receptor M1 (CHRM1), Muscarinic acetylcholine receptor M2 (CHRM2), Muscarinic acetylcholine receptor M3 (CHRM3) (M1, M2, M3 (or CHRM1, CHRM2, CHRM3))

Muscarinic acetylcholine receptors M1, M2, and M3 are members of the G protein-coupled receptor (GPCR) superfamily that mediate the actions of the neurotransmitter acetylcholine in the central and peripheral nervous systems[9][1][3][7]. M1 is primarily located in the central nervous system and is involved in cognition, memory, and other higher functions[2][4]; M2 is chiefly expressed in the heart where it regulates cardiac rate and contractility[2][3]; M3 is abundant in smooth muscle (airway, GI tract, bladder) and exocrine glands, and regulates smooth muscle contraction, glandular secretion, and vasodilation[2][3][5]. These receptors are vital therapeutic targets in a range of diseases such as Alzheimer’s disease, schizophrenia, overactive bladder, COPD, and gastrointestinal disorders, but their high sequence similarity and widespread physiological roles pose challenges for subtype-selective drug development[1][7]. Drugs acting on M1-M3 include nonselective and subtype-selective agonists and antagonists; lack of selectivity can cause wide-ranging adverse effects[1][2][4].

Other names

Muscarinic receptor M1, M2, M3mAChR M1, mAChR M2, mAChR M3Cholinergic receptor, muscarinic 1/2/3CHRM1, CHRM2, CHRM3Acetylcholine receptor, muscarinic type 1/2/3

Agonists: stimulate the receptor, mimicking the action of acetylcholine at muscarinic receptors (signal through G-proteins, subtype dependent)[2][3][8] Antagonists: competitively inhibit acetylcholine binding, blocking normal receptor function[2][8] Some allosteric modulators can enhance or inhibit signaling via non-orthosteric sites[1][7]