Muscarinic Antagonists and Muscarinic Genes (11)
To read the first article in this series, click here.
To read the previous article in this series, click here.
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As many antidepressants antagonize the nicotinic receptors, several antipsychotics antagonize the muscarinic receptors, including haloperidol (brand name Haldol) and chlorpromazine (brand name Thorazine), widely prescribed in in mental health asylums across the US . As one would expect, several natural toxins also antagonize the receptors, including the toxin produces by the African black mamba snake, which antagonize the M1 and M4 receptors, performing roughly the opposite biochemical function of xanomeline.
The muscarinic genes are much less studied than the nicotinic genes, which we shall get to shortly. Nonetheless, we know a little about them. In genome wide association studies, the CHRM1 gene (corresponding to the M1 receptor) has mostly been associated with nicotine dependence. The CHRM2 gene has been associated with alcohol dependence, intelligence (e.g. fascinatingly, rs324650’s T allele is associated with increases of 4.6 IQ points), and depression. CHRM3 has mostly been associated with lung and cardiovascular issues, as well as with schizophrenia. CHRM4 has also been tied to schizophrenia. Finally, CHRM5 has been associated with severity of cigarette smoking, which is interesting, since nicotine does not agonize the M5 receptor.
Now that the reader has been introduced to the muscarinic receptors, we can move on to the far more interesting nicotinic cholinergic receptors.
To return to an overview of the blog series on the cholinergic system, click here.
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