Effects of embryonic glucocorticoid manipulation on adult heart structure Long-term impact of embryonic glucocorticoid receptor (GR) manipulation with either GR agonist dexamethasone (Dex) [100 μM], or targeted translational GR knockdown using morpholino (GR Mo) was assessed in the heart of 120 day post fertilisation (dpf) adult zebrafish. Structural analyses of A) ventricle length, B) weight and C) cavity area were carried out. Data are n = 8 hearts per group, displayed as mean ± SEM analysed by one-way ANOVA with Dunnett's post hoc comparison (*p < 0.05, **p < 0.01, ***p < 0.001). D–F) Histology (haematoxylin and eosin staining) in adult fish hearts D) Controls (Vehicle only control shown here), E) Dex, F) GR Mo.