Tetrodotoxin, frequently abbreviated as TTX, 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 (e.g., blue-ringed octopus, rough-skinned newt, and Naticidae) 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 ions (responsible for the rising phase of an action potential) into the nerve cell.Its mechanism of action, selective blocking of the sodium channel, was shown definitively in 1964 by Toshio Narahashi and professor John W. Moore at Duke University, using Moore's sucrose gap voltage clamp technique.