Muscarinic acetylcholine receptor M1-M5 (mAChR M1-M5)

The muscarinic acetylcholine receptors (mAChRs) are a family of five G protein-coupled receptors (M1–M5) that mediate the metabotropic effects of the neurotransmitter acetylcholine in both the central and peripheral nervous systems (UniProt P11229, P08172, P20309, P08173, P08912). These receptors are involved in a wide array of physiological functions, including the regulation of heart rate, smooth muscle contraction in the gastrointestinal and urinary tracts, and glandular secretions (StatPearls NBK535364). In the context of pan-muscarinic blockade, drugs like trospium chloride act as non-selective competitive antagonists across all five subtypes, though their primary therapeutic utility is the inhibition of M3 receptors to treat overactive bladder (PubChem CID 5284614). Trospium is a quaternary ammonium compound, which limits its ability to cross the blood-brain barrier, thereby reducing central nervous system side effects compared to tertiary amines like oxybutynin (DrugBank DB00240). Despite this relative CNS sparing, systemic antagonism of these receptors frequently leads to peripheral anticholinergic effects such as xerostomia, constipation, and tachycardia. The M1 and M4 subtypes are also significant targets in neuropsychiatric research, particularly for conditions like schizophrenia and Alzheimer's disease (PubMed PMID: 23509613).

Other names

CHRM1CHRM2CHRM3CHRM4CHRM5Muscarinic cholinergic receptorsmAChRsCholinergic receptors muscarinic

Competitive antagonism of acetylcholine at muscarinic M1, M2, M3, M4, and M5 receptors, which inhibits parasympathetic signaling in smooth muscle and glands (StatPearls NBK535364).