Serotonin-selective depletion of HDAC6 alters socioaffective responses to exogenous corticosterone. a, Depiction of the effect of acute Cort (0.5 mg/kg) or vehicle in the social interaction paradigm. Acute Cort, given 20 min before social avoidance testing, triggered the expression of social avoidance (interaction ratio < 100) in WT social defeat-resilient mice but did not affect social approach toward a CD1 target in control mice or in social defeat-vulnerable mice from both genotypes. This permissive effect of Cort on social avoidance was not seen in resilient HDAC6Pet1Cre KO mice (right column; **p < 0.01, compared with vehicle). b, Depicts the effect of Cort or vehicle treatment in the OF and the EPM. Cort injection 20 min before testing induced anxiogenic responses in WT mice (i.e., decreased time spent in the center of the OF and open arms of EPM), while it produced no significant effects or induced anxiolytic-like responses (i.e., increased time spent in the center of an open field) in HDAC6Pet1Cre KO mice (post hoc comparisons, *p < 0.05, ***p < 0.001, compared with vehicle; n = 13–22 per condition). Error bars indicate SEM.