Role of muscarinic acetylcholine receptor subtypes in different organs

Table compiled based on reviews: Racké et al., 2006, Giglio and Tobin, 2009, Eglen, 2012, Matera and Cazzola, 2016, Moran et al., 2019.

Role inM1M2M3M4M5
Central nervous systemEnhance cognitionAntipsychotic effectsInduction of substance use disorder
Occular functionIris sphincter contraction, lacrimal gland secretion
Cardiovascular functionBradycardia (via SA-node)Vasodilation
Gastrointestinal functionGanglionic stimulation of gastric acid secretion, stimulation of salivationenhance M3 mediated contraction of smooth muscleContraction of intestinal smooth muscle, stimulation of salivation
Urinary bladder functionStimulate synaptic ACh release in bladderNot finally clarifiedContraction of detrusor muscle, widening of urethral sphincterInhibit synaptic ACh release in bladder
Pulmonary functionFacilitate neurotransmission in pulmonary ganglia (relevance unclear)Limit ACh release in ganglia (autoreceptor function), attenuate β-agonist relaxationbronchoconstrict, stimulate submucosal gland secretion and ciliary beat frequency
Hormonal functionLimit evoked histamine release from mast cellsInduce release of chemotactic factors from alveolar macrophages