Studies on the role of calcium in the 5-HT-stimulated release of glutamate from C6 glioma cells.
We recently reported that 5-hydroxytryptamine(2A) (5-HT(2A)) receptor activation on cultured glial cells induces glutamate release [J. Neurosci. Res. 67 (2002) 399]. Here we use C6 glioma cells to examine the role of calcium in this response. 5-Hydroxytryptamine (5-HT) increases glutamate release from C6 glioma cells, an effect blocked by low calcium conditions. The calcium ionophores ionomycin and calcimycin also released glutamate from C6 glioma cells in a Ca(2+)-dependent manner. The effect of 5-HT was reduced by the phospholipase C inhibitor U73122 (1-[6[[(17 beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione), but not its inactive enantomer U73343(1-[6[[(17 beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-2,5-pyrrolidinedione). The protein kinase C inhibitors staurosporine and calphostin C had no effect on the response to 5-HT, whereas the response was blocked by thapsigargin and caffeine. Neither the L-type calcium channel blockers, nifedipine and verapamil, nor the N-type calcium channel blocker omega-conotoxin GVIA inhibited the effect of 5-HT, whereas NiCl(2) and KCl blocked the response to 5-HT. We conclude that the 5-HT-induced efflux of glutamate from C6 glioma cells is Ca(2+)-dependent and involves, at least in part, the mobilisation of Ca(2+) from inositol (1,4,5) tris phosphate (IP(3)) sensitive intracellular stores.
Meller
Robert
R
University Department of Clinical Pharmacology, Radcliffe Infirmary, Oxford OX2 6HE, UK. rmeller@downeurobiology.org
Harrison
Paul J
PJ
Sharp
Trevor
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005910:Glioma / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D012701:Serotonin; D018698:Glutamic Acid; D002118:Calcium