FIGURE 2.

Effects of chronic OT and DEX administration on symptomatic characteristics of depression. Chronic OT and DEX administration did not affect locomotor activity in the OFT (A). Chronic DEX administration significantly decreased anxiety‐like behavior and the number of open arm entries in the EPMT, which were prevented by cotreatment with OT (B). Chronic DEX administration significantly increased depression‐like behavior and duration of immobility in the FST, which were reversed by the cotreatment with OT (C). The DEX group showed significantly higher HPA axis activity and plasma CORT levels, which were prevented by cotreatment with OT (D). The OT + DEX group showed significantly higher phosphorylated‐CREB protein expression levels in both the dorsal and ventral hippocampus; however, no significant difference was found between the saline and DEX groups (E). High expression levels of BDNF in the dorsal hippocampus were observed in the DEX and OT + DEX groups compared to those in the saline group (F, left‐hand side). The OT + DEX group showed significantly higher BDNF protein expression levels in the ventral hippocampus; however, no significant difference was found between the saline and DEX groups (F, right‐hand side). The number of animals per group is 8. Bars represent mean ± standard error of the mean. Statistical analysis was performed by one‐way ANOVA followed by Bonferroni/Dunn post hoc tests. *P < 0.05, **P < 0.01 vs. saline group, †P < 0.05, ††P < 0.01 vs. DEX group. DEX, dexamethasone; EPMT, elevated plus maze test; FST, forced swimming test; HPA, hypothalamic–pituitary–adrenal; CORT, corticosterone; OFT, open field test; OT, oxytocin