The mechanism of maitotoxin-induced elevation of the cytosolic free calcium level in rat cerebrocortical synaptosomes.
The present study was conducted to elucidate the mechanism of the maitotoxin (MTX)-induced increase in intrasynaptosomal free calcium level ([Ca2+]i). The MTX (1 ng/ml)-induced increase in [Ca2+]i was partially inhibited by the omission of extracellular Ca2+ (Ca2+e) or the addition of verapamil, but not by adding nifedipine, omega-agatoxin IVA, omega-conotoxin GVIA and omega-conotoxin MVIIC. An increase in [Ca2+]i in the absence of Ca2+e was sensitive to procaine, TMB-8, genistein and verapamil, but not to ryanodine and U-73122. These results may suggest that MTX increases [Ca2+]i by stimulating Ca2+ entry through voltage-independent nonselective cation channels and Ca2+ release from stores through a phospholipase C-gamma1-mediated pathway in rat cerebrocortical synaptosomes.
Department of Pharmacology, University of Obihiro School of Veterinary Medicine, Japan. es@obihiro.ac.jp
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Satoh
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Ishii
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Nishimura
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D019833:Genistein / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008387:Marine Toxins / Q000494:pharmacology*; D035964:Oxocins; D051966:Phospholipase C gamma; D011343:Procaine / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012433:Ryanodine / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism; D000095702:Polyether Toxins
D002118:Calcium; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D004963:Estrenes; D019833:Genistein; D007527:Isoenzymes; D008387:Marine Toxins; D035964:Oxocins; D051966:Phospholipase C gamma; D011343:Procaine; D011505:Protein-Tyrosine Kinases; D011760:Pyrrolidinones; D012433:Ryanodine; D010738:Type C Phospholipases; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C020394:maitotoxin; D000095702:Polyether Toxins