We have investigated whether the intracellular calcium concentration ([Ca
2+]
i) oscillations induced in astrocytes using the metabotropic glutamate-receptor agonist, (1
S,3
R)-1-aminocyclopentane-1,3-dicarboxylic acid (t-ACPD) are Ca
2+-dependent, using three different Ca
2+ indicators with different affinities for Ca
2+. When rat hippocampal cells in culture were loaded with fura-2 (K
d: 145 nM), two-thirds of the cells showed obvious oscillatory increase in [Ca
2+]
i during t-ACPD-administration. Those cells were identified as astrocytes by immuno-histochemistry in our previous paper. In cells loaded with fura-2FF (K
d: 25,000 nM), a similar percentage of t-ACPD-responsive cells showed oscillatory [Ca
2+]
i changes. However, in cells loaded with quin-2 (K
d: 60 nM), t-ACPD induced no oscillatory responses, but some cells showed a small transient increase in the [Ca
2+]
i. The same small transient [Ca
2+]
i increase was seen in cells loaded with both fura-2FF and BAPTA, a Ca
2+ chelator (K
d: 135 nM). These findings indicate the involvement of [Ca
2+]
i-dependent regulatory mechanisms in the induction of the t-ACPD-induced oscillatory change in the [Ca
2+]
i in astrocytes.
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