PDAPP mice exhibited age-dependent amyloid deposition in the brain along with thioflavin-S–positive plaques, including compact plaques with dense cores that were highly reminiscent of those seen in human AD. Dystrophic neurites, reactive astrocytes, and activated microglia were all found near plaques. The process was age-related, in that plaque deposition was minimal at 6 months of age but readily apparent by 9 months, increasing dramatically by 12 to 15 months.13 PDAPP mice were subsequently shown to develop age-related learning defects14 and synapse loss.15
