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Aim:To determine the Ca~(2+)source and cellular mechanisms of spontaneous Ca~(2+)oscillations in hippocampal astrocytes.Methods:The cultured cells were loadedwith Fluo-4 AM,the indicator of intracellular Ca~(2+),and the dynamic Ca~(2+)tran-sients were visualized with confocal laser-scanning microscopy.Results:Thespontaneous Ca~(2+)oscillations in astrocytes were observed first in co-culturedhippocampal neurons and astrocytes.These oscillations were not affected bytetrodotoxin(TTX)treatment and kept up in purity cultured astrocytes.Thespontaneous Ca~(2+)oscillations were not impacted after blocking the voltage-gatedCa~(2+)channels or ethylenediamine tetraacetic acid(EDTA)bathing,indicating thatintracellular Ca~(2+)elevation was not the result of extracellular Ca~(2+)influx.Furthermore,the correlation between the spontaneous Ca~(2+)oscillations and theCa~(2+)store in endoplasmic reticulum(ER)were investigated with pharmacologicalexperiments.The oscillations were:1)enhanced when cells were exposed to bothlow Na~+(70 mmol/L)and high Ca~(2+)(5 mmol/L)solution,and eliminated completelyby 2 μmol/L thapsigargin,a blocker of sarcoplasmic reticulum Ca~(2+)-ATPase;and2)still robust alter the application with either 50μmol/L ryanodine or 400μmol/Ltetracaine,two specific antagonists of ryanodine receptors,but depressed in adose-dependent manner by 2-APB,an InsP_3 receptors(InsP_3R)blocker.Conclusion:InsP_3R-induced ER Ca~(2+)release is an important cellular mechanismfor the initiation of spontaneous Ca~(2+)oscillation in hippocampal astrocytes.
Aim: To determine the Ca 2+ source and cellular mechanisms of spontaneous Ca 2+ oscillations in hippocampal astrocytes. Methods: The cultured cells were loaded with Fluo-4 AM, the indicator of intracellular Ca 2+ , and the dynamic Ca2 + tran-sients were visualized with confocal laser-scanning microscopy. Results: Thespontaneous Ca ~ (2+) oscillations in astrocytes were observed first in co-cultured hippocampal neurons and astrocytes. the oscillations were not affected (TTX) treatment and kept up in the purified cultured astrocytes. Tenspontaneous Ca ~ (2+) lations lations not not not not impacted after blocking the voltage-gated Ca ~ (2+) channels or ethylenediamine tetraacetic acid (EDTA) bathing, indicating that intracellular Ca ~ 2+) elevation was not the result of extracellular Ca ~ (2+) influx.Furthermore, the correlation between the spontaneous Ca ~ (2+) oscillations and the Ca ~ (2+) store in endoplasmic reticulum (ER) were investigated with pharmacologicalexperiments The oscillations were: 1) enhanced when cells wer A blocker of sarcoplasmic reticulum Ca ~ (2 +) - was pretreated with 2 μmol / L thapsigargin, ATPase; and2) still robust alter the application with either 50 μmol / L ryanodine or 400 μmol / Ltetracaine, two specific antagonists of ryanodine receptors, but depressed in adose-dependent manner by 2-APB, an InsP_3 receptors (InsP_3R) blocker.Conclusion: InsP_3R -induced ER Ca ~ (2+) release is an important cellular mechanism for the initiation of spontaneous Ca ~ (2 +) oscillation in hippocampal astrocytes.