The neurotoxin found in water hemlock, plants of the genus Cicuta, is cicutoxin. Water hemlock is among the most dangerously poisonous wild plants, and cicutoxin is present throughout the plant, with especially high concentrations often found in the roots.
Cicutoxin is a naturally occurring C17 polyacetylene that disrupts inhibitory signalling in the central nervous system. It acts as a noncompetitive antagonist of GABA-A receptors, interfering with the brain’s ability to restrain nerve activity. Poisoning may begin rapidly with nausea, vomiting, abdominal pain, tremors, and seizures, and severe cases can progress to respiratory failure.
The name “water hemlock” causes a frequent mix-up with poison hemlock, Conium maculatum. They are unrelated plants from different genera and have different principal toxins: Cicuta contains cicutoxin, while poison hemlock is associated with coniine. Water hemlock also differs from water dropwort, although some Oenanthe species contain closely related polyacetylenes.
Cicuta species grow in wet habitats across parts of North America and Europe. Their roots can be mistaken for edible roots such as parsnip or wild carrot, making accidental foraging particularly dangerous.