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|Section2= |Section3= }} Tetrodotoxin, frequently abbreviated as TTX, is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, 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 the sucrose gap voltage clamp technique. == Sources in nature == Tetrodotoxin has been isolated from widely differing animal species, including western newts of the genus ''Taricha'' (where it was formerly termed "tarichatoxin"), pufferfish, toads of the genus ''Atelopus'', several species of the blue-ringed octopus of the genus ''Hapalochlaena'' (where it was called "maculotoxin"), several sea stars, certain angelfish, a polyclad flatworm, land planarians of the genus ''Bipalium'', several species of Chaetognatha (arrow worms), several nemerteans (ribbonworms) and several species of xanthid crabs. The toxin is variously used as a defensive biotoxin to ward off predation, or as both a defensive and predatory venom (octopuses, chaetognaths and ribbonworms). Even though the toxin acts as a defense mechanism, some predators such as the common garter snake have developed a resistance to TTX, which allows them to prey upon toxic newts. Tarichatoxin and maculotoxin were shown to be identical to tetrodotoxin in 1964 (Mosher et al.) and 1978, respectively. The toxin is produced by bacteria within blue-ringed octopuses. The most common bacteria associated with TTX production are ''Vibrio'' bacteria, with ''Vibrio alginolyticus'' being the most common species. Pufferfish, chaetognaths, and nemerteans have been shown to contain ''Vibrio alginolyticus'' and TTX. The link between these facts and production of TTX in animals has not been firmly established, and there remains much debate in literature as to whether the bacteria are truly the source of TTX in animals.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tetrodotoxin」の詳細全文を読む スポンサード リンク
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