Fig. 1

Experimental design. a The experimental model of episodic systemic inflammation (SI) was developed by six weekly intra-peritoneal injections of lipopolysaccharide (0.3 mg/kg). Long-term outcomes were evaluated 1 week after SI and include behavioral tests, blood and brain cytokine levels, and brain oxidative stress markers. b Body weight was not affected by LPS treatment. c Systemic inflammation was accompanied by monitoring peripheral blood neutrophils in the baseline (before the first LPS injection) and 24 h after the 2nd, the 4th, and the 6th LPS injections. Systemic inflammation was higher in aged mice (aged LPS) compared with young mice submitted to the same treatment and with counts at baseline. d Sickness behavior of young and aged mice was evaluated 24 h after each weekly LPS injection (1st, 2nd, 3rd, 4th, 5th, and 6th LPS injections). Mild sickness behavior was significantly increased in aged mice. Data were plotted as means ± SEM (n = 10–15 per group, from three independent experiments). Statistical analysis with two-way ANOVA and Bonferroni posttest (*p < 0.05, **p < 0.01, ***p < 0.001)