Figure 5From: Transgenic APP expression during postnatal development causes persistent locomotor hyperactivity in the adultAmyloid burden and Aβ levels are slightly delayed by adult onset APP overexpression. A, Silver staining shows forebrain amyloid burden after 2, 4, 6, 9 and 12 mo of transgenic APP overexpression following juvenile (top row) or adult onset (bottom row). B, Quantitation of cortical amyloid burden from silver-stained sections demonstrates that delaying APP overexpression slows initiation of the exponential phase of plaque deposition (p < .001), although once underway the rate of amyloid accumulation is similar in both groups. Post hoc comparisons indicate significant differences in amyloid burden at 9 mo (**p < 0.01) and 12 mo (*p < 0.05) of APP overexpression. n = 3-4 per genotype at each time point. C, D Biochemical measures of Aβ concentration parallel histological measures of amyloid load. After equivalent durations of APP overexpression, adult onset is associated with lower levels of both SDS- and FA-soluble Aβ (Aβ 40 plus 42; p < 0.05 (SDS), p < 0.0001 (FA)). Additionally, the rate of change in FA-soluble Aβ is slower following adult onset (p < 0.001). Post hoc comparisons indicate significant differences in FA-soluble Aβ at 9 mo (*p < 0.05) and 12 mo (***p < 0.001) of APP overexpression. Graphs show mean ± SEM. n = 6-8 per genotype at each time point. Open symbols, juvenile onset; closed symbols, adult onset.Back to article page