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Fig. 4. Multiple mGluR5 agonists fail to trigger astrocytic Ca2+ signaling in adult mice. (A) Experimental setup used for microinjection of agonist in cerebral cortex layer II in anesthetized mice loaded with rhod-2 AM. (B) (Top left) EGFP driven by the astrocyte-specific GLT1 promoter in an adult mouse. (Top right) Time lapse of changes in rhod-2 fluorescence signal (F/F) in response to microinjection of t-ACPD (500 μM). One astrocyte (white arrow) exhibited an increase in rhod-2 signal. (Bottom) Rhod-2 signal changes (F/F) in response to ATP (500 μM) in an adult mouse. White arrows indicate astrocytes that exhibited an increase in Ca2+. (C to E) Histograms comparing (C) number of astrocytes displaying an increase in Ca2+ in response to agonist injections in pups and adult mice, (D) Ca2+ amplitude, and (E) Ca2+ wave velocity and Alexa 488 diffusion velocity (internal control for consistency of agonist injection). **P < 0.01, ***P < 0.001, one-way ANOVA, Bonferroni test; n = 4 to 19 trials.