Tetrodotoxin is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish or mola, and triggerfish, several species that carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other animals. it is actually produced by certain symbiotic bacteria, such as Pseudoalteromonas tetraodonis, certain species of Pseudomonas and Vibrio, as well as some others that reside within these animals. Tetrodotoxin inhibits the firing of action potentials in nerves by binding to the voltage-gated sodium channels in nerve cell membranes and blocking the passage of sodium ionsinto the nerve cell. Tetrodotoxin binds to what is known as site 1 of the fast voltage-gated sodium channel. The binding of any molecules to this site will temporarily disable the function of the ion channel. Saxitoxin, neosaxitoxin and several of the conotoxins also bind the same site.
-V552.gif)