Muskariin

Muskariin is a naturally occurring alkaloid found in various plants, most notably in certain species of fungi. It is a parasympathomimetic agent, meaning it mimics the effects of acetylcholine, a neurotransmitter involved in the parasympathetic nervous system. This action leads to stimulation of muscarinic acetylcholine receptors, which are present in smooth muscle, cardiac muscle, and glands.

In humans and other mammals, muscarinic receptor activation by muskarine can result in a range of physiological responses. These include increased salivation, sweating, lacrimation (tearing), gastrointestinal motility, and bronchoconstriction. At higher doses, it can also cause bradycardia (slow heart rate), hypotension (low blood pressure), and central nervous system effects. The toxicity of muskarine depends on the dose and the route of exposure.

The primary source of concern regarding muskarine is its presence in some poisonous mushrooms. Ingestion of these fungi can lead to muscarine poisoning, a condition characterized by the symptoms described above. While muskarine itself has limited direct medicinal use, its study has been crucial in understanding the function of muscarinic receptors and has contributed to the development of various drugs that target these receptors for therapeutic purposes, such as treating conditions like glaucoma or certain gastrointestinal disorders.