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 in | M1 | M2 | M3 | M4 | M5 |
|---|---|---|---|---|---|
| Central nervous system | Enhance cognition | Antipsychotic effects | Induction of substance use disorder | ||
| Occular function | Iris sphincter contraction, lacrimal gland secretion | ||||
| Cardiovascular function | Bradycardia (via SA-node) | Vasodilation | |||
| Gastrointestinal function | Ganglionic stimulation of gastric acid secretion, stimulation of salivation | enhance M3 mediated contraction of smooth muscle | Contraction of intestinal smooth muscle, stimulation of salivation | ||
| Urinary bladder function | Stimulate synaptic ACh release in bladder | Not finally clarified | Contraction of detrusor muscle, widening of urethral sphincter | Inhibit synaptic ACh release in bladder | |
| Pulmonary function | Facilitate neurotransmission in pulmonary ganglia (relevance unclear) | Limit ACh release in ganglia (autoreceptor function), attenuate β-agonist relaxation | bronchoconstrict, stimulate submucosal gland secretion and ciliary beat frequency | ||
| Hormonal function | Limit evoked histamine release from mast cells | Induce release of chemotactic factors from alveolar macrophages |