[3H]batrachotoxinin-A 20-alpha-benzoate binding to sodium channels in rat brain: sensitivity to tetrodotoxin and divalent cations.
The sodium channel blocker tetrodotoxin partially inhibited [3H]batrachotoxinin-A 20-alpha-benzoate binding to rat brain synaptosomes. This inhibition results from a decrease in the apparent affinity of the radioligand, which indicates that sites 1 and 2 of the sodium channel are not independent as thought previously. Computer-assisted data analysis allowed two binding sites for BTX-B to be distinguished. These sites could be differentiated by means of the divalent cations Mg2+ and Ca2+, that inhibit BTX-B binding completely. Tetrodotoxin diminished the inhibition by Mg2+ and vice versa, suggesting a common mechanism of action for the inhibition.
D000818:Animals; D001496:Batrachotoxins / Q000493:pharmacokinetics*; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D009498:Neurotoxins / Q000493:pharmacokinetics*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology*
D001496:Batrachotoxins; D007473:Ion Channels; D009498:Neurotoxins; D013779:Tetrodotoxin; C031775:batrachotoxinin A 20-alpha-benzoate; D008274:Magnesium; D002118:Calcium