Omega-conotoxin sensitive calcium channels in cerebellar granule cells are not coupled to [3H]glutamate release.
We have studied the biochemical and functional aspects of omega-conotoxin GVIA (omega-CgTx)-sensitive calcium channels in cerebellar granule cells in vitro. 125I-omega-Conotoxin GVIA (125I-omega-CgTx) binding sites were detected in intact cultured cerebellar granule cells and binding parameters were measured (Bmax: 134 fmol/mg protein; kinetic association constant kappa: 3.10(6) M-1.s-1). [3H]Glutamate release was assessed under different release paradigms (namely release triggered by calcium, voltage, and sodium channel agonists) and different times (15 s and 2 min). However, in all cases, [3H]glutamate release was found to be completely insensitive to omega-CgTx. Conversely, voltage-dependent release was inhibited in a dose-dependent fashion by cadmium chloride, with total inhibition at 10(-4) M. These results indicate that N-type calcium channels are not involved in glutamate secretion from granule neurons.
Grignon
S
S
Neurobiologie des Canaux Ioniques, INSERM U374, Faculté de Medecine, Marseille, France.
Seagar
M J
MJ
Couraud
F
F
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D019256:Cadmium Chloride; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism*; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D006098:Granulocytes / Q000187:drug effects* / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014316:Tritium; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002712:Chlorides; D005971:Glutamates; D010455:Peptides; D020960:omega-Conotoxins; D002104:Cadmium; D014316:Tritium; C053423:Conus magus toxin; D018698:Glutamic Acid; D019256:Cadmium Chloride