Explanations are in the Methods section.

Naive animals preferred saccharin over tap water, while untreated, saline-treated and heat-inactivated IL-1ra (iIL-1ra) – treated post-SE rats consumed equal amount of each fluid. IL-1ra restored preference towards saccharin. Data for saccharin are presented as Mean±SEM. *- p<0.05 saccharin solution vs. tap water (t-test).

A. Statistical analysis. Mean±SEM amplitude of faradaic currents recorded from the hippocampus in response to dorsal raphe stimulation was lower in untreated and saline-treated post-SE animals, than in respective naïve subjects, thus indicating compromised raphe-hippocampal serotonergic transmission. This deficit was partially reversed by IL-1ra treatment. *- p<0.05 Post-SE vs. Naive; †- p<0.05 post-SE IL-1ra vs. post-SE saline and post-SE untreated (One-Way ANOVA + Neuman-Keuls post hoc test). B. The waveform of oxidizing current applied to hippocampal carbon fiber electrode. C. Sample oxidative peaks acquired from Saline-treated Control rat, post-SE Saline-treated and post-SE IL-1ra treated animals.

A. Sample snapshots taken from pre-recorded video during FST. Time after the start of the test is indicated on each image. Examples of active swimming which reflects active escape strategies are presented at 1 min 34 s and 1 min 37 s. Note change in the rat's position in the tank which occurred during the 3 s period, and the fuzziness of images due to the animal's movement. Examples of immobility when animals move only enough to avoid drowning, are presented at 2 min 58 s and 3 min 04 s. Note that the animal's position in the tank did not change during 6 s of recording, and that the body is positioned vertically in the water. B. Immobility time in naive and post-SE animals - untreated, treated with saline, heat-inactivated IL-1ra (iIL-1ra) or active IL-1ra. Note the increase in the cumulative immobility time in untreated, saline-treated and iIL-1ra – treated post-SE animals, and its partial reversal following IL-1ra administration. Data are presented as Mean±SEM. *- p<0.05 After SE vs. Before SE (repeated measure ANOVA+Neuman Keuls post hoc test); #- p<0.05 Post-SE vs. Naive; †- p<0.05 Post-SE IL-1ra vs. Post-SE saline (One-Way ANOVA+Neuman Keuls post hoc test).

Since in all three groups of naïve animals all examined parameters were statistically similar for the first and the second assays, in order to simplify the presentation of the findings, the outcome of DEX/CRH test is presented only for the second assay (i.e. during IL-1ra treatment) and data in naive groups are combined for the three treatments (i.e. IL-1ra, saline, and untreated). In saline-treated and untreated rats, SE led to the increase of baseline plasma CORT level; failure of DEX to decrease CORT concentration; and the exacerbated and longer-lasting response to CRH (since the responses in two groups were statistically close, the data are combined for presentation purposes). IL-1ra decreased baseline plasma CORT level and partially normalized the outcome of DEX/CRH test. Data are presented as Mean±SEM. Even though data for some groups were combined, statistical comparisons were done between respective groups: #- p<0.05 Post-SE-Saline and Post-SE untreated vs. respective Naïve controls and at respective time points; †- p<0.05 post-SE IL-1ra vs. Naive IL-1ra; ‡- p<0.05 post-SE IL-1ra vs. post-SE Saline and post-SE untreated (One-Way ANOVA + Neuman-Keuls post hoc test). *- p<0.05; **- p<0.01; ***- p<0.001 comparison within the same groups, for two adjacent time points between which the symbols are located (Repeated measure ANOVA + Neuman-Keuls post hoc test).