Organic neurotoxins in seafoods.

Toxins formed by organic micro-organisms may accumulate within certain tissues of predacious sea animals, which may serve as a source of seafood poisoning for the higher food chain. Such toxins are distinct from inorganic chemicals or infectious agents which may have contaminated the seafoods. Distinct clinical syndromes have emerged, and the individual toxins have been identified. Clinical manifestations of each begin with a gastrointestinal prodrome and headache, followed by sensorimotor deficits. Bulbar and cognitive changes are associated with the more lethal tetrodotoxin, saxitoxin, and domoic acid toxin. Tetrodotoxin and saxitoxin block sodium channels, while ciguatoxin opens them. Domoic acid stimulates excitatory amino acids at the NMDA receptors.