The role of intracellular Na+ and mitochondria in buffering of kainate-induced intracellular free Ca2+ changes in rat forebrain neurones.
1. We have examined the mechanisms by which cultured central neurones from embryonic rat brain buffer intracellular Ca2+ loads following kainate receptor activation using fluorescent indicators of [Ca2+]i and [Na+]i. 2. Stimulation of cultured forebrain neurones with 100 microM kainate produced a rapid increase in [Ca2+]i that displayed a variable rate of recovery. Kainate also increased [Na+]i with a response that was slightly slower in onset and markedly slower in recovery. 3. The recovery of [Ca2+]i to baseline was not very sensitive to the [Na+]i. The magnitude of the increase in [Na+]i in response to kainate did not correlate well with the [Ca2+]i recovery time, and experimental manipulations that altered [Na+]i did not have a large impact on the rate of recovery of [Ca2+]i. 4. The recovery of [Ca2+]i to baseline was accelerated by the mitochondrial Na+-Ca2+ exchange inhibitor CGP-37157, suggesting that the recovery rate is influenced by release of Ca2+ from a mitochondrial pool and also that variation in the recovery rate is related to the extent of mitochondrial Ca2+ loading. Kainate did not alter the mitochondrial membrane potential. 5. These studies reveal that mitochondria have a central role in buffering neuronal [Ca2+]i changes mediated by non-N-methyl-D-aspartate (NMDA) glutamate receptors, and that the variation in recovery times following kainate receptor activation reflects a variable degree of mitochondrial Ca2+ loading. However, unlike NMDA receptor-mediated Ca2+ loads, kainate receptor activation has minimal effects on mitochondrial function.
Hoyt
K R
KR
Department of Pharmacology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Stout
A K
AK
Cardman
J M
JM
Reynolds
I J
IJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002998:Clonazepam / Q000031:analogs & derivatives / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D005456:Fluorescent Dyes; D007608:Kainic Acid / Q000494:pharmacology*; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D016548:Prosencephalon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000502:physiology*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors; D013268:Stimulation, Chemical; D013841:Thiazepines / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D005456:Fluorescent Dyes; D016194:Receptors, N-Methyl-D-Aspartate; D019831:Sodium-Calcium Exchanger; D013841:Thiazepines; D002998:Clonazepam; C079032:CGP 37157; D012964:Sodium; D007608:Kainic Acid; D002118:Calcium