Muscarinic acetylcholine receptor M2

Muscarinic acetylcholine receptor M2

Cholinergic receptor, muscarinic 2

Human M2 muscarinic acetylcholine receptor/lysozyme fusion protein. PDB [1]
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols  ; HM2
External IDs IUPHAR: ChEMBL: GeneCards:
Species Human Mouse
RefSeq (mRNA)
RefSeq (protein)
Location (UCSC)
PubMed search

The muscarinic acetylcholine receptor M2, also known as the cholinergic receptor, muscarinic 2, is a muscarinic acetylcholine receptor that in humans is encoded by the CHRM2 gene.[2] Multiple alternatively spliced transcript variants have been described for this gene.[2]



The M2 muscarinic receptors are located in the heart, where they act to slow the heart rate down to normal sinus rhythm after stimulatory actions of the sympathetic nervous system, by slowing the speed of depolarization. They also reduce contractile forces of the atrial cardiac muscle, and reduce conduction velocity of the atrioventricular node (AV node). However, they have no effect on the contractile forces of the ventricular muscle.


A Dutch family study found that there is "a highly significant association" between the CHRM2 gene and intelligence as measured by the Wechsler Adult Intelligence Scale-Revised.[3] A similar association was found independently in the Minnesota Twin and Family Study.[4][5]

However, a larger 2009 study attempting to replicate this claim instead found no significant association between the CHRM2 gene and intelligence.[6]

Mechanism of action

M2 muscarinic receptors act via a Gi type receptor, which causes a decrease in cAMP in the cell, generally leading to inhibitory-type effects. They appear to serve as autoreceptors.[7]

In addition, they modulate muscarinic potassium channels.[8][9] In the heart, this contributes to a decreased heart rate. They do so by the G bèta gamma subunit of the G protein coupled to M2. This part of the G protein can open K+ channels in the parasympathetic notches in the heart, which causes an outward current of potassium, which slows down the heart rate.


Few highly selective M2 agonists are available at present, although there are several non-selective muscarinic agonists that stimulate M2, and a number of selective M2 antagonists are available.


  • Bethanechol (nonselective muscarinic agonist)
  • (2S,2'R,3'S,5'R)-1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine 3-sulfoxide methyl iodide (selective for M2 but only partial agonist)[10]
  • Berberine


See also


  1. ^ Haga K, Kruse AC, Asada H, Yurugi-Kobayashi T, Shiroishi M, Zhang C, Weis WI, Okada T, Kobilka BK, Haga T, Kobayashi T (February 2012). "Structure of the human M2 muscarinic acetylcholine receptor bound to an antagonist". Nature 482 (7386): 547–51.  
  2. ^ a b "Entrez Gene: CHRM2 cholinergic receptor, muscarinic 2". 
  3. ^ Gosso MF, van Belzen M, de Geus EJ, Polderman JC, Heutink P, Boomsma DI, Posthuma D (November 2006). "Association between the CHRM2 gene and intelligence in a sample of 304 Dutch families". Genes Brain Behav. 5 (8): 577–84.  
  4. ^ Comings DE, Wu S, Rostamkhani M, McGue M, Lacono WG, Cheng LS, MacMurray JP (January 2003). "Role of the cholinergic muscarinic 2 receptor (CHRM2) gene in cognition". Mol. Psychiatry 8 (1): 10–1.  
  5. ^ Dick DM, Aliev F, Kramer J, Wang JC, Hinrichs A, Bertelsen S, Kuperman S, Schuckit M, Nurnberger J, Edenberg HJ, Porjesz B, Begleiter H, Hesselbrock V, Goate A, Bierut L (March 2007). "Association of CHRM2 with IQ: converging evidence for a gene influencing intelligence". Behav. Genet. 37 (2): 265–72.  
  6. ^ Lind PA, Luciano M, Horan MA, Marioni RE, Wright MJ, Bates TC, Rabbitt P, Harris SE, Davidson Y, Deary IJ, Gibbons L, Pickles A, Ollier W, Pendleton N, Price JF, Payton A, Martin NG (September 2009). "No association between Cholinergic Muscarinic Receptor 2 (CHRM2) genetic variation and cognitive abilities in three independent samples". Behav. Genet. 39 (5): 513–23.  
  7. ^ Douglas CL, Baghdoyan HA, Lydic R (December 2001). "M2 muscarinic autoreceptors modulate acetylcholine release in prefrontal cortex of C57BL/6J mouse". J. Pharmacol. Exp. Ther. 299 (3): 960–6.  
  8. ^ a b c d e f Rang HP (2003). Pharmacology. Edinburgh: Churchill Livingstone.  
  9. ^ Boron, W. F and Boulpaep, E. L. (2005). Medical Physiology. Philadelphia: Elsevier Saunders. p. 387.  
  10. ^ Scapecchi S, Matucci R, Bellucci C, Buccioni M, Dei S, Guandalini L, Martelli C, Manetti D, Martini E, Marucci G, Nesi M, Romanelli MN, Teodori E, Gualtieri F (March 2006). "Highly chiral muscarinic ligands: the discovery of (2S,2'R,3'S,5'R)-1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine 3-sulfoxide methyl iodide, a potent, functionally selective, M2 partial agonist". J. Med. Chem. 49 (6): 1925–31.  
  11. ^ Edwards Pharmaceuticals, Inc.; Belcher Pharmaceuticals, Inc. (May 2010), DailyMed, U.S. National Library of Medicine, retrieved January 13, 2013 
  12. ^ Melchiorre C, Angeli P, Lambrecht G, Mutschler E, Picchio MT, Wess J (December 1987). "Antimuscarinic action of methoctramine, a new cardioselective M-2 muscarinic receptor antagonist, alone and in combination with atropine and gallamine". Eur. J. Pharmacol. 144 (2): 117–24.  

Further reading

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.