What Muscarine Is
Muscarine is a natural alkaloid found in certain mushrooms. The highest concentrations occur in species such as Inocybe and Clitocybe. Amanita muscaria contains only trace amounts, but the compound was first isolated from this mushroom in the 19th century, which gave it its name.
Chemically, muscarine is a quaternary ammonium compound that resembles acetylcholine, the neurotransmitter responsible for many parasympathetic nervous system functions. Because of this structural similarity, it binds to muscarinic acetylcholine receptors in the body.
How Muscarine Works
Muscarine acts as a selective agonist of muscarinic receptors. These receptors are located in smooth muscles, the heart, and various glands. When muscarine binds to them, it stimulates the parasympathetic nervous system. Unlike many psychoactive compounds, muscarine does not cross the blood-brain barrier, so its effects remain limited to the peripheral nervous system.
Physiological Effects
Symptoms of muscarine exposure generally appear within 30 minutes to two hours after ingestion of mushrooms containing the compound. They include:
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Excess salivation and sweating
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Increased tear production
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Constricted pupils
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Slowed heart rate
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Abdominal cramping, nausea, vomiting, and diarrhea
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Shortness of breath or tightness in the chest
This cluster of symptoms is sometimes summarized as SLUDDE: salivation, lacrimation, urination, diaphoresis (sweating), diarrhea, and emesis (vomiting).
Severity of Poisoning
In most cases, muscarine poisoning is uncomfortable but not fatal. The greatest risks are in individuals with heart or respiratory conditions, as muscarine can cause low blood pressure, dangerous bradycardia, or breathing difficulties. High doses may lead to convulsions or death, though such outcomes are rare.
Treatment
The standard medical treatment for muscarine poisoning is administration of atropine. Atropine is a muscarinic receptor antagonist, which blocks muscarine’s effects. Supportive care, such as rehydration and monitoring of heart rate and breathing, may also be necessary.
Muscarine vs. Muscimol
Although muscarine and muscimol are both found in Amanita muscaria, they act on very different systems:
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Muscarine stimulates the parasympathetic nervous system and causes strong bodily effects such as sweating, salivation, and nausea.
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Muscimol acts on the central nervous system by binding to GABA-A receptors. This produces sedative, hypnotic, and hallucinogenic effects.
In Amanita muscaria, muscarine is present only in trace amounts. The psychoactive effects of the mushroom are primarily due to muscimol and ibotenic acid.
Historical and Scientific Importance
Muscarine was the first parasympathomimetic compound discovered and played a significant role in early studies of the nervous system. Its ability to mimic acetylcholine helped scientists understand receptor subtypes and their role in controlling involuntary bodily functions.
Key Points
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Muscarine is a natural alkaloid found in some toxic mushrooms.
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It activates muscarinic acetylcholine receptors in the parasympathetic nervous system.
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Effects include sweating, salivation, slowed heart rate, and digestive distress.
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Atropine is the main antidote.
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Muscarine is not psychoactive and should not be confused with muscimol.