Muscarinic acetylcholine receptor M1 and M2 (CHRM1/CHRM2)

Muscarinic acetylcholine receptors M1 and M2 are G protein-coupled receptors (GPCRs) that mediate the physiological actions of acetylcholine in the central and peripheral nervous systems (UniProt P11229, P08172). The M1 receptor (CHRM1) is highly expressed in the CNS, particularly in the cortex and hippocampus, where it is vital for cognitive functions like memory and learning (PubMed PMID: 28934319). The M2 receptor (CHRM2) is primarily located in the heart, where it mediates bradycardia, and on presynaptic nerve terminals where it acts as an autoreceptor to inhibit further acetylcholine release (StatPearls NBK544293). Oxybutynin is a non-selective muscarinic antagonist used primarily to treat overactive bladder by inhibiting M3-mediated detrusor contraction, but it also binds with high affinity to M1 and M2 receptors (PubChem CID 4634). Antagonism of M1 receptors by oxybutynin is associated with cognitive side effects, especially in elderly patients, while M2 antagonism can lead to increased heart rate (PubMed PMID: 15027866). These receptors are key therapeutic targets for managing smooth muscle hyperactivity, though their widespread distribution necessitates careful dosing to avoid systemic anticholinergic toxicity (NIH LiverTox).

Other names

M1 muscarinic receptorM2 muscarinic receptorCholinergic receptor muscarinic 1Cholinergic receptor muscarinic 2CHRM1CHRM2

Competitive antagonism of muscarinic acetylcholine receptors