Pro-inflammatory cytokine levels after chronic LPS-induced inflammatory stress. IL1-β (A), TNF-α (B) and IL-6 (C) levels in cortex (CO) and hippocampus (HI) from LPS-treated mice (0.5mg/kg of LPS every 3 days for 3 months) or control (0.9% NaCl every 3 days for 3 months) by using ELISA assay. Treatment started at 3 months and mice were sacrificed at 6 months of age. Cytokine levels were expressed in pg/mg protein. Results are mean±SEM for 6 mice in each group. **p < 0.01, ***p < 0.001 compared to control mice by a Mann-Whitney test.