ryanodine and maitotoxin

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.

Topics: Animals; Calcium; Calcium Channel Blockers; Calcium Channels; Cerebral Cortex; Cytosol; Dose-Response Relationship, Drug; Enzyme Inhibitors; Estrenes; Female; Genistein; Isoenzymes; Male; Marine Toxins; Oxocins; Phospholipase C gamma; Procaine; Protein-Tyrosine Kinases; Pyrrolidinones; Rats; Rats, Wistar; Ryanodine; Synaptosomes; Type C Phospholipases