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BIOL 1F25 - Lec 5

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Brock University
Nicholas D Vesprini

Lecture 5 Toxins -Neurotoxins: toxic substances that act on neurons; many act on ion channels in the nerve cell membrane 1. Tetrodotoxin (TTX): works on the outside of voltage gated sodium channels 2. Essential for transmission of action potential (electrical signal) down axon -voltage-gated sodium and potassium channels are necessary for nerve conduction -activation and appropriate inactivation of these channels is essential for proper nerve conduction in the body 3. When these channels are blocked by a toxin, action potentials cannot travel down the axon, nerve firing fails and nerves cannot transmit messages to muscles, diaphragm, lungs, and other vital organs, etc. Puffer Fish and TTX -puffer fish found in tropical waters of Japan, Indian Ocean, south Pacific and even North American waters -considered delicacy in Japan (and described as the most delicious of all fishes) can be up to $400 US per meal -consumption of meat produces a pleasant warm tingling but can cause death where you can think clearly but cannot speak or move and soon cannot breath -symptoms can occur 15 minutes to several hours after ingestion -initial symptoms: tingling of tongue and mouth -death can occur within 4-6 hours, typically from respiratory muscle paralysis -there is no proven antidote; activated charcoal minimizes absorption of toxin -about 60% of puffer poisoning prove fatal -the amount contained in one fish is said to be enough to kill more than 30 people; because of its potency it is said to be about 1250 times more deadly than cyanide -TTX is heat stable -puffer fish have a change in the protein sequence of the Na channel that causes them to be highly resistant to TTX TTX also found in… -California newts, gastropod molluscs (snail-like), skin of Atelopid frogs, some species of eastern sal
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