Effects of selegiline on plasma corticosterone concentrations in CD157 KO mice subjected to the FST. (A) The FST induced a significant increase in plasma corticosterone concentrations in both WT and CD157 KO mice, and plasma corticosterone concentrations in WT mice after the FST were higher than those of CD157 KO mice. There were no significant differences in baseline plasma corticosterone concentrations between WT and CD157 KO mice. Data are expressed as mean ± SEM (n = 11−16). ****P < 0.001 vs. non-treatment mice and +P = 0.062 vs. WT after FST (Dunnett’s test). A two-way ANOVA showed main effects of FST (F(1,49) = 50.861, P < 0.001) and genotype (F(1,49) = 4.632, P < 0.05) without significant interaction between the effects of FST and genotypes on plasma corticosterone concentrations (F(1,49) = 0.858, P = 0.359). (B) A single administration of selegiline (1−10 mg/kg, s.c.) elevated post-FST plasma corticosterone concentrations in CD157 KO mice to the WT post-FST level. Data are expressed as mean ± SEM (n = 10−12). **P < 0.01, saline-treated CD157 KO mice vs. saline-treated WT mice (Student’s t-test), #P < 0.05 vs. saline-treated CD157 KO mice (Dunnett’s test), F(3,40) = 3.100, P < 0.05. Selegiline (3 mg/kg, s.c.) nonsignificantly elevated post-FST plasma corticosterone concentrations in CD157 KO mice (P = 0.051). A two-way ANOVA showed no statistically significant interaction between the effects of selegiline and genotypes on plasma corticosterone concentration (F(3,81) = 2.025, P = 0.117).