Figure 1. Astrocyte Ca²⁺ responses to mGluR agonist application are attenuated IP₃R2^−/− slices.

A. Neocortical brain slices from IP₃R2^+/+ (left panel) and IP₃R2^{− /−} (right panel) mice were loaded with the Ca²⁺-sensitive fluorophore Rhod-2/AM and astrocytes were identified by dye uptake, morphology and location. Ca²⁺ fluorescence was measured in the region of interest (green arrow) and is displayed at 3 time points in relation to 1S,3R-ACPD treatment: (a) before, (b) at peak response and (c) after. White outline indicates the region of magnification in C. Scale bar: 20 µm. B. Fluorescence intensity signals for the Ca²⁺ fluorescence measured in the soma of the indicated astrocytes. Signals were corrected for background that was measured in an identical area immediately adjacent to the region of interest. Representative single traces of the Ca²⁺ response in soma of IP₃R2^+/+ astrocytes (left trace) and IP₃R2^{− /−} (right trace) are shown and the duration of 1S, 3R-ACPD application is indicated below the traces. C. Z-stack of 12 images encompassing 12 mm of depth in IP₃R2^+/+ (left panel) and IP₃R2^{− /−} (right panel) brain slices. This demonstrates the ameboid shape of the astrocyte soma which extends a foot process near a neighboring arteriole. Scale Bar: 10 µm. D. Cumulative probability histograms of population responses are shown. Peak (left panel) and integrated (right panel) Ca²⁺ responses of IP₃R2^+/+ (open circles, 58 cells) and IP₃R2^{− /−} (filled circles, 63 cells) astrocytes with inset bar graphs indicating the mean ± S.E.M. Nine slices were prepared from four mice for each genotype.