Premium
Quantitative evaluation of mitochondrial calcium content in rat cortical neurones following a glutamate stimulus
Author(s) -
Brocard Jacques B.,
Tassetto Michel,
Reynolds Ian J.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0793h.x
Subject(s) - glutamate receptor , nmda receptor , depolarization , mitochondrion , stimulation , stimulus (psychology) , kainate receptor , calcium , biophysics , chemistry , biology , neuroscience , biochemistry , medicine , receptor , ampa receptor , psychology , organic chemistry , psychotherapist
1 Recent observations showed that a mitochondrial Ca 2+ increase is necessary for an NMDA receptor stimulus to be toxic to cortical neurones. In an attempt to determine the magnitude of the Ca 2+ fluxes involved in this phenomenon, we used carbonylcyanide‐ p ‐(trifluoromethoxy)phenylhydrazone (FCCP), a mitochondrial proton gradient uncoupler, to release mitochondrial free calcium ([Ca 2+ ] m ) during and following a glutamate stimulus, and magfura‐2 to monitor cytoplasmic free calcium ([Ca 2+ ] c ). 2 FCCP treatment of previously unstimulated neurones barely changed [Ca 2+ ] c whereas when added after a glutamate stimulus it elevated [Ca 2+ ] c to a much greater extent than did exposure to glutamate, suggesting a very large accumulation of Ca 2+ in the mitochondria. 3 Mitochondrial Ca 2+ uptake was dependent on glutamate concentration, whereas the changes in the overall quantity of Ca 2+ entering the cell, obtained by simultaneously treating neurones with glutamate and FCCP, showed a response that was essentially all‐or‐none. 4 Mitochondrial Ca 2+ uptake was also dependent on the nature and duration of a given stimulus as shown by comparing [Ca 2+ ] m associated with depolarization and treatment with kainate, NMDA or glutamate. Large mitochondrial Ca 2+ accumulation only occurred after a glutamate or NMDA stimulus. 5 These studies provide a method of estimating the accumulation of Ca 2+ in the mitochondria of neurones, and suggest that millimolar concentrations of Ca 2+ may be reached following intense glutamate stimulation. It was shown that substantially more Ca 2+ enters neurones following glutamate receptor activation than is reflected by [Ca 2+ ] c increases.