Na+/Ca2+ exchanger modulates kainate-triggered Ca2+ signaling in Bergmann glial cells in situ.
The role of sodium-calcium exchanger in calcium homeostasis in Bergmann glial cells in situ was investigated by monitoring cytoplasmic calcium ([Ca2+]i) and sodium ([Na+]i) concentrations. The [Ca2+]i and [Na+]i transients were measured either separately by using fluorescent indicators fura-2 and SBFI, respectively, or simultaneously using the indicators fluo-3 and SBFI. Since the removal of extracellular Na+ induced a relatively small (approximately 50 nM) elevation of [Ca2+]i, the Na+/Ca2+ exchanger seems to play a minor role in regulation of resting [Ca2+]i. In contrast, kainate-triggered [Ca2+]i increase was significantly suppressed by lowering of the extracellular Na+ concentration ([Na+]o). In addition, manipulations with [Na+]o dramatically affected the recovery of the kainate-induced [Ca2+]i transients. Simultaneous recordings of [Ca2+]i and [Na+]i revealed that kainate-evoked [Ca2+]i transients were accompanied with an increase in [Na+]i. Moreover, kainate induced significantly larger [Ca2+]i and smaller [Na+]i transients under current-clamp conditions as compared to those recorded when the membrane voltage was clamped at -70 mV. The above results demonstrate that the Na(+)-Ca2+ exchanger is operative in Bergmann glial cells in situ and is able to modulate dynamically the amplitude and kinetics of [Ca2+]i signals associated with an activation of ionotropic glutamate receptors.
Kirischuk
S
S
Max-Delbruck-Centre for Molecular Medicine, Berlin-Buch, Germany.
Kettenmann
H
H
Verkhratsky
A
A
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology*; D051379:Mice; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D018690:Excitatory Amino Acid Agonists; D019831:Sodium-Calcium Exchanger; D000255:Adenosine Triphosphate; D012964:Sodium; D007608:Kainic Acid; D002118:Calcium