The role of metabotropic glutamate receptors for the generation of calcium oscillations in rat hippocampal astrocytes in situ.
Ca2+ oscillations are part of the intra- and intercellular signalling in many cell types. We have studied Ca2+ oscillations in astrocytes in acute brain slices of the hippocampus of juvenile rats (postnatal 8-14 days old), using confocal laser scanning microscopy and bulk-loading of the Ca2+ -sensitive dye Fluo-4. Astrocytes were identified morphologically in the stratum radiatum, and by their Ca2+ response in the absence of external K+. Thirty-five per cent of astrocytes (43 slices) showed spontaneous Ca2+ oscillations, with a frequency of 1.26 +/- 0.11 transients/min (n = 366). These Ca2+ signals were unaffected by tetrodotoxin (0.5 microM) and Ni2+ (2 mM), but were sensitive to interference with the phospholipase C-mediated Ca2+ release from intracellular stores. Spontaneous Ca2+ oscillations were reduced or suppressed by antagonists of metabotropic glutamate receptors (mGluRs) of groups I and II, but not affected by antagonists of group III. Glutamate (1-100 microM) and specific agonists of mGluR groups I and II evoked concentration-dependent Ca2+ signals, which were oscillatory at intermediate concentrations (e.g. at 10 microM glutamate). Our results indicate that mGluRs of both groups I and II are involved in mediating Ca2+ oscillations in astrocytes, which might be glial responses to micromolar changes of glutamate in the extracellular spaces.
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Robin
R
Abteilung für Allgemeine Zoologie, FB Biologie, Technische Universität, Postfach 3049, D-67653 Kaiserslautern, Germany.
Deitmer
Joachim W
JW
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004396:Coloring Agents; D004594:Electrophysiology; D005110:Extracellular Space / Q000187:drug effects / Q000502:physiology; D018755:GABA Agonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D018408:Patch-Clamp Techniques; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000502:physiology*
D004396:Coloring Agents; D018755:GABA Agonists; D018094:Receptors, Metabotropic Glutamate; D018698:Glutamic Acid