Figure 2.

At low doses, ADP induces microglial process extension. A, Tomato lectin stained PTC microglia before (CTRL, left) and after bath application of ADP (10 μm, 15 min, right). Red represents change maximal cross-sectional area (z stacks 50 μm, 1 μm). B, Lateral view shows microglial processes extended toward the upper surface of the slice. Red arrows indicate bulbous endings at their tips. C, ADP at low doses induces process emergence and extension from an amoeboid cell. Images are control (CRTL, left) and ADP (10 μm, 15 min, middle). Right, Merge image represents color-coded differences between CTRL and ADP images. Red represents new signal; green represents lost signal; yellow represents maintained signal (z stack 20 μm, 1 μm). Right, Inset, Bulbous endings (red arrow) at the tips of processes. D, ADP induces process extension of a ramified microglia. Control (CRTL, left), ADP (10 μm, 15 min middle), and color-coded differences between them (merge image, right). Red represents new signal; green represents lost signal; yellow represents maintained signal (z stack 20 μm, 1 μm, scale bar 10 μm). Inset, Bulbous endings (red arrow) at process tips. E, Time course of changes in mean cross-sectional area induced by 10 μm ADP in 7 amoeboid microglia. F, Time course of changes in mean cross-sectional area induced by 10 μm ADP in 7 ramified microglia. G, Mean and SE of the latency to 20% increase in cross-sectional area induced by ADP for amoeboid (n = 7) and ramified microglia (n = 7). Process extension by ramified cells occurred at a significantly longer latency (t test, p = 0.009**). Movie 1 shows process extension of an amoeboid cell induced by low-dose ADP.