Fig. 4. Monoamine concentrations (A,D), main monoamine metabolite concentrations (B,E) and the ratio of concentrations of main metabolite to parent monoamine (monoaminergic activity; C,F) for serotonin (A–C) and dopamine (D–F) in the telencephalon of rainbow trout Oncorhynchus mykiss treated with cortisol. Cortisol was administered by intraperitoneal implant on its own (`implant', 50 mg hydrocortisone 21-hemisuccinate kg^–1 fish) or simultaneously with the glucocorticoid receptor blocker RU486 (500 mg mifepristone kg^–1 fish); an additional group of untreated fish served as a control group. Values are means ± 1 S.E.M.; N=10–12 for the control group, N=10 for the group given cortisol implants, and N=9–10 for the cortisol implant + RU486 treatment group. Treatment groups that do not share a letter were significantly different from one another (one-way ANOVA on ranks followed by Dunn's post hoc multiple comparisons test; P values, A<0.001, B=0.014, C=0.008, D=0.086, E=0.057, F=0.021).