Figure 7.

Astrocyte processes in Cx30-CreERT2; R26-lsl-GCaMP3 mice reliably and rapidly respond to odor stimulation well before the onset of functional hyperemia. (a) Left, OSN terminals labeled with CaRuby-Nano (red) delineate glomerular boundaries (dotted lines; g1–g3), whereas GCaMP3 labeling at this stage (5–11 d.p.i.) is evident but weak and diffuse (green). Scale bar, 50 µm. Right, in response to odor stimulation (black bar), OSN inputs to two of the three glomeruli (g1 and g3) are activated (black traces), but it is difficult to resolve astrocyte responses (gray traces). Resolution: 1.1 µm per pixel, 271 ms per frame. (b) Average images from higher-resolution recordings of glomerulus g3. An astrocyte soma is visible at the periphery of the glomerulus (arrow). ROIs (dotted lines) outline OSNs terminating in the glomerulus (center, red) and astrocyte processes (right, green). Responses from the astrocyte soma are collected within the ROI labeled ‘s’. Scale bar, 20 µm. (c) Average of four trials showing the Ca²⁺ response of OSNs (black) and astrocytes (gray) to 3 s of odor stimulation with amyl acetate. The astrocyte soma (blue) does not respond. Resolution: 0.8 µm per pixel, 55 ms per frame. (d) Ensemble average of responses from all glomeruli (n = 13 glomeruli from 7 mice) showing the onset and duration of Ca²⁺ responses of OSNs (black) and astrocyte processes (gray). All traces were aligned by the onset of the OSN responses. Error bars show s.e.m.