Fig. 4. Social interaction tests.

a Social interaction tests: percent time interacting with the novel social target following acute social defeat was significantly less for both groups compared to before the defeat experience. Moreover, the Mann–Whitney test revealed that: (1) inoculated mice spent significantly greater (p ≤ 0.05*) percent time interacting with the novel social target compared to control mice before acute social defeat. (2) On average, percent time interacting with the novel social target was significantly greater (p < 0.01**) for inoculated mice compared to control mice. b Correlation: percent time defending during acute social defeat significantly positively correlated with percent time interacting with the novel social target presented during the second social interaction test taking place following the defeat. Results presented as mean ± s.e.m, a, bp ≤ 0.05*, ap < 0.01**, a Wilcoxon signed-rank test within each group, b non-parametric Spearman’s rank correlation coefficient, r = 0.5, an = 12 per group, bn = 24.