Pro-inflammatory cytokine levels after acute LPS-induced inflammatory stress. IL-1β, TNF-α and IL-6 levels in cortex (A, B, C, respectively) and hippocampus (D, E, F, respectively) of mice treated with a single () or two () or three () i.p. injections of LPS at 10mg/kg or vehicle (0.9% NaCl) were measured by ELISA assay. Mice were sacrificed 2, 4, 6 or 12 h after a single injection or 24 h after two or three injections. Cytokine levels were expressed in pg/mg protein. Results are mean±SEM for 6 mice in each group. *p < 0.05, **p < 0.01, ***p < 0.001 compared to 0.9% NaCl-injected mouse group by Kruskal-Wallis test with a Dunns multiple comparison test.