5XFAD mice have elevated levels of activated Caspase-3 in neurons of Layer 5 cortex and subiculum. Parasagittal brain sections from 1.5, 4, and 9 month old 5XFAD mice were co-incubated with antibodies against activated Caspase-3 (green) and neuron-specific class III β-tubulin (red; A-F) or NeuN (red; G-L) and imaged by confocal microscopy. Sections were co-stained with DAPI to detect nuclei (blue). Co-immunolabeling with neuronal markers β-tubulin and NeuN demonstrate Caspase-3 activation in 5XFAD neurons. Note the presence of activated Caspase-3 labeling in proximal dendrites of large pyramidal neurons of Layer 5 cortex and subiculum at 1.5 and 4 months (A-D, G-J), The number of Caspase-3-positive proximal dendrites is reduced in 9 month old compared to younger 5XFAD mice, although Caspase-3 aggregates are more prevalent at older ages suggesting a progressive process (spherical green structures in E, F, K, L). Activated Caspase-3-positive aggregates become apparent at 4 months in Layer 5 cortex and later in subiculum, and likely represent neuronal apoptotic bodies. Arrows in F point to Caspase-3-positive aggregates that co-label with neuron-specific class III β-tubulin. Scale bar = 20 μm.