Fig. 2

(A) Whole-body cortisol concentrations in wild-type (WT) and mc2r knockout (mc2r^KO) zebrafish following acute stress exposure. Fish were subjected to repeated air exposure stress (3 × 2 min) and sampled 30 min after the final exposure. Cortisol was extracted and quantified using a radioimmunoassay (RIA) validated for zebrafish by Cortes et al., 2018. The data are presented as the means ± SEM (n = 20 per genotype per condition; 5 fish per tank, 4 tanks). Statistical analysis was performed via two-way ANOVA (*P < 0.05). Asterisks indicate significant differences between the control and stressed groups within the same genotype, whereas different letters denote significant differences between genotypes. (B) Effects of intraperitoneal injection of ACTH (20 and 100 µg/g body weight) in WT and mc2r^KO animals. Sham animlas were injected with saline whereas CTRL were not manipulated before euthanizing them in MS222 oversdose. Data represent the means ± SEM (n = 7 per treatment and genotype). Statistical analysis was performed via two-way ANOVA and different letters indicate significant differences at p < 0.05.