Inflammatory response after LPS exposure. Mice were injected with lipopolysaccharide (LPS) at time zero and plasma levels of TNFα, IL-1β, IL-6 and HMGB-1 were measured by ELISA. TNFα was increased after 30 minutes and peaked at 2 hours, returning to baseline thereafter. (a) * P < 0.01; *** P < 0.001 vs naïve. IL-1β was detected after two hours from LPS administration and levels continued to steadily increase until 24 hours. (b) *** P < 0.001 vs naïve. IL-6 expression was highly elevated at two hours, decreasing at six hours but still significantly detectable at 24 hours compared with naïve animals. (c) *** P < 0.0001; ** P < 0.001 vs naïve respectively. Levels of HMGB1 started to increase at day 1 and until day 3. (d) ** P < 0.001; *** P < 0.0001 vs naïve. Increased mRNA expression of (e) IL-1β and (f) IL-6 was found at six hours after peripheral LPS injection in the hippocampus of mice using quantitative PCR (P < 0.001 vs naïve); mRNA expression returned to normal by day 1. Data are expressed as mean ± standard error of the mean (n = 6) and compared by one-way analysis of variance and Student-Newman-Keuls method.