Levels of presenilin 1 (PS1), holoprotein (48 kDa), and CTF fragment (18 kDa) of senescence-accelerated mouse prone 8 (SAMP8), SHAP(−), SHAP(+), and amyloid precursor protein/presenilin 1 (APP/PS1) mice. Bars represent mean ± standard error of the mean (SEM); values are adjusted to 100 % for levels of SAMP8. Analysis of variance (ANOVA) following Tukey’s multiple comparison test: **p < 0.01 vs. SAMP8; $
p < 0.05, $$
p < 0.01 vs. APP/PS1; #
p < 0.05, ##
p < 0.01 vs. SHAP(−)