Figure 5. β2AR stimulation decreases microglia surveillance regardless of amyloid pathology but becomes ineffective with age in V1.

a Representative in vivo two-photon time projected images from CX3CR1^GFP/+ and CX3CR1^GFP/+5xFAD^+/− mice. Images obtained before treatment are shown in magenta and superimposed on images obtained after saline or clenbuterol injection which are shown in green (scale bar = 25μm). Plaque-associated microglia (outlined in yellow) were manually selected based on proximity to MeX04⁺ plaques (not shown). b-d Quantification of microglial surveillance fraction (area of image covered by microglia post/pre) in Saline (green) and Clenbuterol (magenta) treatment groups in CX3^G/+ and 5xFAD CX3^G/+ mice (b: 4 months; c: 6 months; d: 9 months). e Representative individual microglia prior to and after clenbuterol treatment used for Sholl analysis. f Representative curves showing Sholl pro les of microglia pre- (black) and post- (magenta) clenbuterol treatment in CX3^G/+ mice at 4 months old. g-i Quantification of ratio of microglia total intersections from Sholl analysis post/pre treatment. Both CX3^G/+ and 5xFAD CX3^G/+ microglia retract their processes in response to clenbuterol at 4 and 6 months but not at 9 months (g: 4 months; h: 6 months; i: 9 months). n = 9–11 mice per genotype per age group. Two-way ANOVA with Bonferroni (b-d) or Tukey (g-i) correction; *p<0.05, **p<0.01, ***p<0.001.