Tetrodotoxin, frequently abbreviated as TTX, is a potent neurotoxin with no known antidote. There have been successful tests of a possible antidote in mice, but further tests must be carried out to determine efficacy in humans. Fampridine has been shown to reverse tetrodotoxin toxicity in animal experiments. Tetrodotoxin blocks action potentials in nerves by binding to the voltage-gated, fast
sodium channels in nerve cell membranes, essentially preventing any affected nerve cells from firing by blocking the channels used in the process. The binding site of this toxin is located at the pore opening of the voltage-gated Na+ channel. Its name derives from Tetraodontiformes, the name of the order that includes the pufferfish, porcupinefish, ocean sunfish or mola, and triggerfish, several
species of which 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.