Muscarinic acetylcholine receptor
There are two different types of acetylcholine receptor – the nicotinic and muscarinic receptors. The muscarinic receptors are further classified into M1–M5 subtypes. The M1 receptors are widely distributed throughout the neurones of the central nervous system. Coupled to stimulatory G-proteins, M1 muscarinic acetylcholine receptors have a stimulatory effect on neurotransmission when bound by an agonist. M3 and M5 receptor subtypes also have a stimulatory effect on the target tissue, whereas the M2 and M4 subtypes are inhibitory.
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References
Cholinergic transmission. In: Pharmacology, 4th edition. Rang HP, Dale MM and Ritter JM. Edinburgh, UK: Harcourt Publishers Ltd, 2001:110–138.