The levels of water-soluble Aβ in APP23 Tg mice and control littermate brains. The values were quantified by europium immunoassay (EuIA) at the same ages as in Figure 1. Solid lines, Tg mice; broken lines, control mice. (A) Aβ40. (B) Aβ42. (C) The Summation of Aβ40 and Aβ42. Notice the high levels of soluble Aβ in the Tg mice, already evident at 2 months of age, relative to the control animals.