Muskarin

Muskarin is a naturally occurring alkaloid classified as a muscarinic cholinergic agonist. It was first isolated from the fly agaric mushroom (Amanita muscaria) and the death cap mushroom (Amanita phalloides). Chemically, muskarin is part of the tropane alkaloids and exhibits structural similarity to acetylcholine, the body's primary neurotransmitter in the parasympathetic nervous system.

Muskarin binds specifically to muscarinic acetylcholine receptors (mAChRs), which are G protein-coupled receptors located in various tissues, including the heart, smooth muscles, and glands. Activation of these receptors by muskarin results in parasympathetic effects such as bradycardia, increased glandular secretion, and smooth muscle contraction. Due to its potent biological activity, muskarin has been used in scientific research to study cholinergic mechanisms and receptor pharmacology.

Poisoning from muskarin can occur through ingestion of contaminated mushrooms or accidental exposure and presents with symptoms consistent with excessive parasympathetic stimulation. These include salivation, lacrimation, urination, diarrhea, gastrointestinal distress, and emesis, collectively known as SLUDGE. In severe cases, muskarin poisoning may lead to hypotension, bronchoconstriction, and cardiovascular collapse.

Antidotal treatments for muskarin poisoning generally involve the use of atropine, a muscarinic receptor antagonist that counteracts the effects of muskarin. Due to its potency and toxicity, muskarin is handled with caution in laboratory settings and is not used therapeutically in humans.

Muskarin exemplifies the complex interactions between natural compounds and biological receptors, highlighting the importance of understanding these mechanisms for both toxicology and pharmacology.