Actions of 4-epitetrodotoxin and anhydrotetrodotoxin on the squid axon.
The actions of the newly discovered 4-epitetrodotoxin and of anhydrotetrodotoxin have been studied on the internally perfused squid giant axon under voltage-clamped conditions. Both compounds are selective in blocking only the sodium channel. The concentration for reducing the sodium current to one-half is 13.2 nM for 4-epitetrodotoxin and 298 nM for anhydrotetrodotoxin. Compared with tetrodotoxin, the relative potencies are 0.39 for 4-epitetrodotoxin and 0.018 for anhydrotetrodotoxin. The results suggest that hydrogen bonding at C-4 and C-9 is an important contributing force in binding to the membrane receptor site.
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Kao
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Yasumoto
D000818:Animals; D001369:Axons / Q000187:drug effects*; D049832:Decapodiformes; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D010477:Perfusion; D013779:Tetrodotoxin / Q000494:pharmacology* / Q000031:analogs & derivatives
D007473:Ion Channels; C047739:anhydrotetrodotoxin; D013779:Tetrodotoxin