The balance between inhibitory and excitatory hilar interneurons depends on age, sex, and apoE isoform.

<p><b><i>A–D</i></b>, Histograms showing the number of hilar neurons positive for GAD67 (purple), calretinin (grey), or NeuN (blue) in female (<b><i>A, B</i></b>) and male (<b><i>C, D</i></b>) apoE3-KI (<b><i>A, C</i></b>) or apoE4-KI (<b><i>B, D</i></b>) mice at 1, 3, 6, 12, and 16 months of age (n = 6−12 mice per group). <b><i>E-F</i></b>, Ratios of GAD67-positive interneurons to calretinin-positive mossy cells in the hilus of the dentate gyrus of female (<b><i>E</i></b>) and male (<b><i>F</i></b>) apoE-KI mice at 1, 3, 6, 12, and 16 months of age (n = 6−12 mice per group). *<i>p</i><0.05 (<i>t</i>-test).