Muscarinic M2, M3, and M5 receptors (M2, M3, M5)

Muscarinic acetylcholine receptor M2, M3, and M5 are members of the muscarinic receptor subtype family, each encoded by distinct CHRM genes and performing specific roles throughout the body. M2 receptors are located predominantly in the heart and act to decrease heart rate and contractility by inhibiting cAMP signaling via Gi proteins[1][2][5]. M3 receptors are abundant in smooth muscle (airways, gastrointestinal tract, bladder) and glands, activating Gq-mediated pathways to stimulate muscle contraction and secretions[1][2][6][7]. M5 receptors, the least understood, are mainly found in the CNS (substantia nigra), involved in dopamine regulation, and are now an emerging drug target for neuropsychiatric conditions and addiction[1][3]. All three are targets of clinically used antimuscarinic drugs, which block the action of acetylcholine to produce therapeutic effects in conditions such as bradycardia, asthma/COPD, overactive bladder, and some CNS disorders. Their broad physiological distribution leads to significant side-effect profiles when not targeted selectively[1][2][3][4].

Other names

Muscarinic receptor M2, M3, M5mAChR M2, mAChR M3, mAChR M5Cholinergic receptor muscarinic M2, M3, M5

Antagonists block acetylcholine binding, inhibiting receptor-mediated G protein activation and downstream signaling. Selective antagonists (e.g., tiotropium for M3/M5) produce tissue-specific effects (e.g., bronchodilation via M3 blockade). Allosteric modulators can enhance or dampen receptor activity by binding non-orthosteric sites.