Table 1.
Muscarinic acetylcholine receptor subtypes. Primary signaling mechanisms and examples of tissue types expressing muscarinic receptor subtypes are listed.
| Subtype | Gene | Mechanism of Signaling | Tissue Distribution |
|---|---|---|---|
| M1 | CHRM1 | Inositol phosphates | CNS 1, GI tract, lymphocytes |
| M2 | CHRM2 | Inhibition of adenylyl cyclase | Heart, smooth muscle (along stomach, bladder, airways, etc.), CNS |
| M3 | CHRM3 | Inositol phosphates | CNS, GI tract, smooth muscle |
| M4 | CHRM4 | Inhibition of adenylyl cyclase | CNS |
| M5 | CHRM5 | Inositol phosphates | CNS, esophageal smooth muscle, lymphocytes, salivary gland |
1 CNS, central nervous system; GI, gastrointestinal.