Astrocytic coverage of asymmetric synapses in DTg mice. (A, B) Electron micrographs of the CA1 stratum radiatum of the hippocampus of WT (A) and DTg mice (B). Colors indicate the classification of astrocytic coverage of asymmetric synapses: pink, synapses without astrocytic contact; blue, synapses with astrocytic contact; yellow, astrocytic processes. (C, D) Box-and-whisker plots showing pooled data for percent of synapses without astrocytic contact (each box has lines at the lower quartile, median, and upper quartile values, and whiskers indicating the range). Percent of synapses without astrocytic contact was significantly increased in DTg mice [P = 0.001, Kruskal Wallis test for 3 groups] (C), but was comparable to WT after Dox treatment starting at 1 mo of age (Dox*) [P = 0.012, Kruskal Wallis test for 3 groups] (D). *P < 0.05, **P < 0.01, ***P < 0.001, two-tailed Mann–Whitney U test.