Intracerebroventricular administration of PA to TgCRND8 and wild-type mice increases extracellular and intracellular Aβ. Aβ species were measured 16 h after icv administration of PA to TgCRND8 mice (A, B) and wild-type mice (C, D). A, B) Levels of Tris-soluble extracellular (A) and RIPA-soluble intracellular (B) Aβ40 and Aβ42 were increased in transgenic mouse brains after PA injection. C, D) Levels of endogenous rodent Aβ40 and Aβ42 were also increased in extracellular (C) and intracellular (D) fractions of wild-type mouse brains after PA injection. Intracellular Aβ from wild-type mice was purified and concentrated by solid-phase extraction before measurement by ELISA (for TgCRND8 mice, n = 8 for Aβ40 and n = 10 for Aβ42; for wild-type mice, n = 6 for all groups). ****P < 0.0001.