Mitochondria accumulate Ca2+ following intense glutamate stimulation of cultured rat forebrain neurones.
1. In cultures of rat forebrain neurones, mitochondria buffer glutamate-induced, NMDA receptor-mediated Ca2+ influx. Here, we have used the fluorescent calcium indicator, indo-1 AM to record [Ca2+]i from single cells. We varied either the glutamate concentration or the duration of exposure to investigate the cellular mechanisms recruited to buffer [Ca2+]i within different stimulation protocols. 2. For a 15 s stimulus, the recovery time doubled as the glutamate concentration was raised from 3 to 300 microM. Changing the duration of exposure from 15 s to 5 min increased the recovery time tenfold even when the glutamate concentration was held at 3 microM. 3. We used a selective inhibitor of the mitochondrial Na(+)-Ca2+ exchange, CGP-37157. When applied immediately after a 15 s, 100 microM glutamate challenge, CGP-37157 consistently caused a rapid fall in [Ca2+]i followed by a slow rise after the drug was washed out. A similar pattern was seen with the 5 min, 3 microM glutamate stimulus. The effects of CGP-37157 are consistent with the release of substantial mitochondrial Ca2+ stores during recovery from an intense glutamate stimulus. 4. These studies suggest that mitochondria become progressively more important for buffering glutamate-induced Ca2+ loads as the stimulus intensity increases. The recovery of [Ca2+]i to baseline following glutamate removal is critically regulated by the release of Ca2+ from mitochondrial stores via mitochondrial Na(+)-Ca2+ exchange. The data highlight a previously under-appreciated role for [Na+]i in the regulation of [Ca2+]i in central neurones.
White
R J
RJ
Center for Neuroscience, University of Pittsburgh School of Medicine, PA 15261, USA.
Reynolds
I J
IJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects*; D011247:Pregnancy; D016548:Prosencephalon / Q000187:drug effects*; D051381:Rats
D018698:Glutamic Acid; D002118:Calcium