Omega-conotoxin GVIA inhibits release of noradrenaline from rat hippocampal slices in the absence of extracellular calcium.
Slices of hippocampus of the rat, preincubated with [3H]noradrenaline ([3H]NA), were used to investigated the effects of omega-conotoxin GVIA (omega-CTX) on the release of [3H]NA evoked by 3,4-diaminopyridine (3,4-DAP, 200 microM), veratridine (0.7 microM) or monensin (0.01 microM) in the absence of extracellular CA2+. The 3H outflow, evoked by 3,4-DAP or veratridine, was inhibited by tetrodotoxin (TTX) or omega-CTX but the 3H outflow evoked by monensin was neither affected by TTX nor by omega-CTX in Ca(2+)-free medium, containing 1 mM EGTA. The release response to 3,4-DAP or veratridine was also blocked by omega-CTX in a concentration-dependent manner in Ca(2+)-free medium, containing 2.5 mM Mg2+ and the blockade was still complete after washing for 20 min with omega-CTX-free medium. The findings suggest that, under these conditions, the toxin might also block sodium channels.
Huang
H Y
HY
Shanghai Institute of Physiology, Chinese Academy of Sciences.
D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008985:Monensin / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology; D020866:omega-Conotoxin GVIA
D000631:Aminopyridines; D002121:Calcium Channel Blockers; D010456:Peptides, Cyclic; D013779:Tetrodotoxin; D014701:Veratridine; D008985:Monensin; D020866:omega-Conotoxin GVIA; C038615:2,3-diaminopyridine; D008274:Magnesium; D002118:Calcium; D009638:Norepinephrine