FST was performed 2 hr after ketamine treatment with three different dosages (5, 20, and 50 mg/kg). Ketamine significantly reduces immobility at 5 mg/kg, but not at 20 and 50 mg/kg, compared to saline-treated control (one-way ANOVA, F(3, 35) = 3.005, p = 0.0434, n = 9 ~ 10 per group). Graphs represent mean ± S.E.M., **, p < 0.05.