Muscarinic acetylcholine receptor

Muscarinic acetylcholine receptors, or muscarinic receptors (mAChRs), are acetylcholine receptors that form G protein-coupled receptors in the cell membranes of certain neurons and other cells. They play several roles, including acting as the main end-receptor stimulated by acetylcholine released from postganglionic fibers in the parasympathetic nervous system.

Subtypes

There are five muscarinic acetylcholine receptor subtypes:

• M1 receptors, also known as simply mAChRs
• M2 receptors
• M3 receptors
• M4 receptors
• M5 receptors

ME/CFS

In 2015, a relatively large German study found 29% of ME/CFS patients had elevated autoantibodies to M3 and M4 muscarinic acetylcholine receptors, as well as β2 adrenergic receptors.

In 2020, a small Sweden study confirmed these results in two different patient cohorts. The study assessed patients with moderate ME who met the Canadian and international consensus criteria for ME, plus the Systemic Exertion Intolerance Disease criteria, and found that the majority of patients had raised blood plasma concentration of β1 and β2 adrenergic receptor autoantibodies, and M3 and M4 muscarinic receptor autoantibodies. Levels in cerebrospinal fluid levels were normal. Only 25% of healthy controls had raised autoantibody levels. These findings supported the autoimmune hypothesis for a subset of patients.

Notable studies

• 2016, Antibodies to β adrenergic and muscarinic cholinergic receptors in patients with Chronic Fatigue Syndrome - (Full text)
• 2020, Autoantibodies to beta-adrenergic and muscarinic cholinergic receptors in Myalgic Encephalomyelitis (ME) patients – A validation study in plasma and cerebrospinal fluid from two Swedish cohorts - (Full text)

Articles and blogs

• 2015, Autobodies found in a subset of CFS patients - #MEAction

See also

• Acetylcholine
• Adrenergic receptor
• Autoimmune hypothesis
• Neurotransmitter

Learn more

• Muscarinic receptors - autonomic neurons - Oxford Academic Press
• Targeting Muscarinic Acetylcholine Receptors for the Treatment of Psychiatric and Neurological Disorders (2019)

cell membrane A very thin membrane, composed of lipids and protein, that surrounds the cytoplasm of a cell and controls the passage of substances into and out of the cell.

See myalgic encephalomyelitis.

See chronic fatigue syndrome.

autoantibody An antibody that works against the body's own antigens, a hallmark of autoimmune diseases. Autoantibodies are the opposite of an antibodies.

plasma The liquid part of blood, lymph, or milk after removing any suspended material. Most of the time, "plasma" simply refers to blood, after all the blood cells have been removed. If you also remove the clotting factors, then the plasma is referred to as "serum".

An antibody that works against the body's own antigens, a hallmark of autoimmune diseases. Autoantibodies are the opposite of an antibodies.

autoantibody An antibody that works against the body's own antigens, a hallmark of autoimmune diseases. Autoantibodies are the opposite of an antibodies.

antibodies Antibody/immunoglobulin refers to any of a large number of specific proteins produced by B cells that act against an antigen in an immune response.

β / Β. Greek letter beta (a symbol used in science), equivalent to "b".

β β / Β. Greek letter beta (a symbol used in science), equivalent to "b".

Involving the neurotransmitter acetylcholine. Cholinergic side effects include diarrhea, blurred vision, decreased intraocular pressure, contricted pupil in the eyes, sweating, increased saliva and mucus on the lungs, bronchial constriction, increased gastrointestinal tone, decreased blood pressure, slow heart rate, and contraction of bladder detrusor muscle. muscle spasms/cramps, low blood pressure, slowed heart rate, nausea and vomiting, increased saliva and sweating, shortness of breath, and urinating more often.

cholinergic Involving the neurotransmitter acetylcholine. Cholinergic side effects include diarrhea, blurred vision, decreased intraocular pressure, contricted pupil in the eyes, sweating, increased saliva and mucus on the lungs, bronchial constriction, increased gastrointestinal tone, decreased blood pressure, slow heart rate, and contraction of bladder detrusor muscle. muscle spasms/cramps, low blood pressure, slowed heart rate, nausea and vomiting, increased saliva and sweating, shortness of breath, and urinating more often.

autoantibody An antibody that works against the body's own antigens, a hallmark of autoimmune diseases. Autoantibodies are the opposite of an antibodies.

β β / Β. Greek letter beta (a symbol used in science), equivalent to "b".

myalgic encephalomyelitis (M.E.) - A disease often marked by neurological symptoms, but fatigue is sometimes a symptom as well. Some diagnostic criteria distinguish it from chronic fatigue syndrome, while other diagnostic criteria consider it to be a synonym for chronic fatigue syndrome. A defining characteristic of ME is post-exertional malaise (PEM), or post-exertional neuroimmune exhaustion (PENE), which is a notable exacerbation of symptoms brought on by small exertions. PEM can last for days or weeks. Symptoms can include cognitive impairments, muscle pain (myalgia), trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, among others. An estimated 25% of those suffering from ME are housebound or bedbound. The World Health Organization (WHO) classifies ME as a neurological disease.