Figure 1 Photomicrographs of H&E-stained sections of the hippocampus: (a) A photomicrograph of a coronal section in the hippocampus proper at the CA1 area of an adult rat aged 8 months showing the major two parts of the hippocampal formation hippocampus proper and dentate gyrus (DG) with narrow hippocampal sulcus (HS) in between. The hippocampus proper is composed of four areas (CA–C1 to CA–C4) (×40). (b) Three layers of the hippocampus: the molecular (M), pyramidal (P), and polymorphic (PM) layers; the pyramidal layer is formed of multiple regular rows of the pyramidal cells (×100). (c) The pyramidal cells appeared triangular in shape with large vesicular nuclei and basophilic cytoplasm. Notice: oligodendroglia cells (black arrows), astrocytes (red arrows), microglia (arrow head), nerve fibers (F), and blood vessels (BV) (×400). (d) Typical pyramidal cells as large triangular cells with basophilic cytoplasm, large vesicular nuclei, and prominent nucleoli (N). Notice: oligodendroglia cells (black arrow) (×1000). (e) A photomicrograph of a rat aged 22 months showing more degenerated pyramidal cells in the pyramidal cell layer (red arrows) and others still normal (black arrows). Notice: vacuolated areas (V) (×400). (f) A photomicrograph of a rat aged 26 months showing disturbed arrangement with a large number of degenerated shrunken pyramidal cells (black arrows). Notice: vacuolations (V) (×400).