mAChR

Muscarinic acetylcholine receptors (mAChR) mediate diverse physiological functions. At present, five receptor subtypes (M(1) - M(5)) have been identified. The odd-numbered receptors (M(1), M(3), and M(5)) are preferentially coupled to G(q/11) and activate phospholipase C, which initiates the phosphatidylinositol trisphosphate cascade leading to intracellular Ca(2+) mobilization and activation of protein kinase C. On the other hand, the even-numbered receptors (M(2) and M(4)) are coupled to G(i/o), and inhibit adenylyl cyclase activity. They also activate G protein-gated potassium channels, which leads to hyperpolarization of the plasma membrane in different excitable cells.