Figure 9.

Dynamin-independent endocytosis in astrocytes is enhanced by glutamate and amyloid-β peptide. A, B, FM images of astrocytes in control (A) or pretreated with glutamate (1 mm; 5 min) (B). Glutamate significantly enhanced the uptake of FM dye. C, FM image of astrocytes pretreated with mGluR antagonist MCPG (200 μm) before and during glutamate stimulation. D, Normalized intensity of FM signal under control, glutamate, and glutamate plus MCPG conditions. Glutamate significantly increased the FM intensity (310 ± 20% of control; n = 20; ***p < 0.001), but the enhancement was blocked by pretreatment with MCPG (110 ± 10%; n = 17; p > 0.3). Error bars indicate SEM. E, Ca²⁺ imaging traces showing transient increase of intracellular Ca²⁺ in astrocytes induced by glutamate application (1 mm). F, Pretreatment with MCPG (200 μm) blocked the Ca²⁺ increase induced by glutamate application. G–I, FM images of astrocytes under control (G), pretreatment with reverse peptide Aβ42–1 (50 μm; 20 min) (H), or active peptide Aβ1–42 (50 μm; 20 min) (I). J, Normalized intensity of FM signal under different treatments. FM intensity significantly increased in Aβ1–42 treatment group (150 ± 10% of control; n = 12; **p < 0.002) compared with the mock treatment with Aβ42–1 (92 ± 8% of control; n = 13). K, Ca²⁺ imaging traces showing intracellular Ca²⁺ increase in astrocytes induced by application of Aβ1–42 (50 μm). Scale bars: A–C, G–I, 50 μm.