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. Author manuscript; available in PMC: 2019 May 1.
Published in final edited form as: Brain Behav Immun. 2018 Mar 7;70:257–267. doi: 10.1016/j.bbi.2018.03.005

Figure 1. Sickness behavior is increased by prior stress in male and female rats.

Figure 1

(A) Male and female rats underwent inescapable stress (100 trials of tailshock) or remained in the home cage. 24 h later rats received a single IP injection of 10 ug/kg LPS or saline (vehicle-control) and then underwent behavioral testing (see methods for additional details on timing). Male and female rats are graphed separately to simplify interpretation but sex was analyzed as a variable in both the sucrose preference and social exploration tests. (B) Male and (C) female rats demonstrated reduced sucrose preference following stress. Furthermore, prior stress exaggerated the LPS induced reduction in sucrose preference in both male and female rats. Juvenile social exploration was reduced by both stress and LPS in (D) male and (E) female rats. Furthermore, female rats had lower levels of social investigation as compared to male rats. Sucrose preference results were analyzed for each day using a 2 × 2 × 2 ANOVA with sex, stress, and immune challenge as the between subjects factors (n = 6 per group with a total of 48 rats). Results from the juvenile social exploration test were analyzed using 2 × 2 × 2 repeated measures ANOVAs with sex, stress, and immune challenge as the between subject factors and time as the within subjects factor. Data are expressed as mean ± SEM. †main effect of sex, *main effect of stress, #main effect of LPS, p < 0.05 in all cases. Abbreviations: JSE (juvenile social investigation), SA (sucrose anhedonia), LPS (lipopolysaccharide).