A–D , Levels of soluble ( A , B ) and insoluble Aβ ( C , D ) in cortical homogenates from PDAPP mice expressing human apolipoprotein E alleles at different ages. A , ^& p < 0.001 versus all other groups, ANOVA, Tukey–Kramer post test, *p < 0.05, ***p < 0.001 t test. B , ^& p < 0.001 versus all other groups except E4 at 12 months, ^# p < 0.05 versus E3 at 12 months ANOVA, Tukey–Kramer post test, **p < 0.01, t test. C , ^& p < 0.001 versus all other groups, ANOVA, Tukey–Kramer post test, *p < 0.05, **p < 0.01, ***p < 0.001, t test. D , ^& p < 0.001 versus all other groups, ANOVA, Tukey–Kramer post test, *p < 0.05, **p < 0.01, ***p < 0.001, t test.