Figure 3: Calcium waves in APPPS1 mice.

(a) Intercellular calcium events in APPPS1 mice. Astrocytes were identified by SR101 and OGB-1 co-labelling (a nearby plaque is also labelled by SR101 (solid circle)). Time-lapse images in this example show that a calcium signal first appears in an astrocyte soma (dashed circle), and subsequently spreads to neighbouring astrocyte somata and processes (arrows and dashed circles). Scale bar, 30 μm. (b) Frequency, velocity and distance travelled of intercellular calcium events in APPPS1 mice. (c,d) For comparison, we triggered calcium waves by microiontophoresis of ATP in wild-type littermates (n=8 waves involving n=42 astrocytes in n=2 mice). In this example, astrocytes were labelled with OGB-1 AM and identified by SR101 (not shown). The electrode (indicated by dashed lines in the upper left corner) was filled with ATP and Alexa 594 (red fluorescence, not shown). ATP was delivered in the second image (indicated by asterisk) and triggered a calcium wave with a concentric wavefront. Accordingly, calcium transients at the wavefront were detectable simultaneously in astrocytes at equidistance to the electrode tip (1 and 2; 3 and 4), but successively in astrocytes at different distances to the electrode tip (1–3–5–6; onsets are indicated by black arrowheads on top of corresponding calcium traces; the black vertical dashed line indicates the time point of the right image). Scale bar, 100 μm. The velocity of ATP-evoked calcium waves is given in d.