Figure 1.
Experimental groups and time lines.
In protocol 1, the effect of IP injected vehicle (VEH) and LPS on depression-like behavior in the FST was assessed 1 and 28 days post-injection. In protocol 2, the depression-related effect of vehicle and LPS was assessed with the sucrose preference (SP) test during days −1–4 and days 26–27 post-injection.
Figure 2.
Effect of LPS (0.83 mg/kg injected IP), relative to vehicle (VEH), on the body weight of CD1 mice as measured immediately before and 1 day (A) as well as 28 days (B) after treatment under single and group housing conditions.
The graphs show the change in weight (weight after treatment minus weight before treatment). The values are means+SEM, n = 8. *** P<0.01 versus change in weight following treatment with vehicle.
Figure 3.
Effect of LPS (0.83 mg/kg injected IP), relative to vehicle (VEH), on the body weight of C57BL/6 mice as measured immediately before and 1 day (A) as well as 28 days (B) after treatment under single and group housing conditions.
The graphs show the change in weight (weight after treatment minus weight before treatment). The values are means+SEM, n = 7–8. *** P<0.01 versus change in weight following treatment with vehicle.
Figure 4.
Effect of LPS (0.83 mg/kg injected IP), relative to vehicle (VEH), on the behavior of CD1 mice in the FST as recorded 1 and 28 days after treatment under single and group housing conditions.
The graphs show (A) the duration of immobility, (B) the duration of swimming, and (C) the duration of climbing, these parameters being expressed as a percentage of the total test duration. The values are means+SEM, n = 8. * P≤0.1, *** P<0.01 versus vehicle-treated mice at the same time point post-treatment. In panel B (Single) it was not possible to apply a post-hoc test because two-way ANOVA failed to disclose any interaction between the factors time and treatment.
Figure 5.
Effect of LPS (0.83 mg/kg injected IP), relative to vehicle (VEH), on the behavior of C57BL/6 mice in the FST as recorded 1 and 28 days after treatment under single and group housing conditions.
The graphs show (A) the duration of immobility, (B) the duration of swimming, and (C) the duration of climbing, these parameters being expressed as a percentage of the total test duration. The values are means+SEM, n = 8. ** P<0.05, *** P<0.01 versus vehicle-treated mice at the same time point post-treatment, ++ P<0.05, +++ P<0.01 versus vehicle-treated mice tested 28 days post-treatment. In panels A (Single), B (Single) and C (Single) it was not possible to apply a post-hoc test because two-way ANOVA failed to disclose any interaction between the factors time and treatment.
Figure 6.
Effect of LPS (0.83 mg/kg injected IP), relative to vehicle (VEH), on plasma concentrations of corticosterone as recorded 1 and 28 days after treatment under single and group housing conditions.
Trunk blood of CD1 (A) and C57BL/6 (B) mice for the corticosterone assay was taken 30 min after the FST had been started. The values are means+SEM, n = 7–8. *** P<0.01 versus vehicle-treated mice at the same time point post-treatment, + P≤0.1, +++ P<0.01 versus vehicle-treated mice tested 1 day post-treatment. In panel A it was not possible to apply a post-hoc test because two-way ANOVA failed to disclose any interaction between the factors time and treatment.
Figure 7.
Effect of LPS (0.83 mg/kg injected IP), relative to vehicle (VEH), on plasma concentrations of interleukin-6 as recorded 1 and 28 days after treatment under single and group housing conditions.
Trunk blood of CD1 (A) and C57BL/6 (B) mice for the interleukin-6 assay was taken 30 min after the FST had been started. The values are means+SEM, n = 7–8. ** P<0.05, *** P<0.01 versus vehicle-treated mice at the same time point post-treatment.
Figure 8.
Effect of (A) vehicle (VEH) and (B) LPS (0.83 mg/kg injected IP) on the daily consumption of sucrose (1%) solution and normal tap water in singly housed C57BL/6 mice.
The main graphs show the absolute daily intake of sucrose solution and water (ml). In the inserts, the daily intake of sucrose solution and water on the day before treatment (day -1) and on day 26 post-treatment is expressed as a percentage of the total daily fluid intake. The values are means±SEM, n = 7. *** P<0.01 versus water intake.
Figure 9.
Effect of vehicle (VEH) and LPS (0.83 mg/kg injected IP) on the total daily intake of fluid in singly housed C57BL/6 mice.
The graph shows the absolute daily intake of fluid on the day before treatment (day -1) and on days 1, 2 and 26 post-treatment. The values are means+SEM, n = 7. ** P<0.05, *** P<0.01 versus vehicle on the same day, +++ P<0.01 versus vehicle on all other days.