Figure 8.

Purinergic receptor agonists mobilize cytosolic Ca ²⁺ in astrocytic end-foot processes. A, Preparation of freshly prepared cortical brain slices (P15) used for multiphoton imaging. Last frame visualizes GFAP immunoreactivity (green) and nuclear staining (Sytox, blue) of the same slide used for Ca ²⁺ imaging in B. Red arrowheads depict two GFAP-positive astrocytes with vascular processes that responded to ATP exposure. B, Increases in cytosolic Ca ²⁺ evoked by local application of ATP (100 μm) around the same vessel. The vessels were visualized by intracardial injection of Texas Red Dextran immediately before slide preparation. Fluo-4/AM is in green; Texas Red Dextran is in red. Red arrowheads depict the GFAP-positive astrocytes in A, last frame. C, Focal field stimulation (2 sec pulse, 100 Hz, 100 μA) evokes a Ca ²⁺ wave that propagates along the vessel wall (red arrowhead indicates stimulation electrode; dotted line indicates medium-sized vessel). Astrocytes engaged in the Ca ²⁺ wave are indicated by yellow arrowheads and numbered according the sequence that they engage in Ca ²⁺ signaling. D, Relative increases in Fluo-4/AM signal (ΔF/F) of the astrocytes numbered in C. Scale bar: A, B, 20 μm; C, 40 μm.