Muscarinic acetylcholine receptors are known as cell receptors.
 The alpha subunit of the G-protein activates guanylate cyclase (inhibiting the effects of intracellular cAMP) while the beta-gamma subunit activates the K-channels and therefore hyperpolarize the cell
== Origin and evolution ==ACh receptors are related to GABA, glycine, and 5-HT3 receptors and their similar protein sequence and gene structure strongly suggest that they evolved from a common ancestral receptor

