Acute Stress Effects Over Time on the Stress Axis in the Carp ( <i>Cyprinus carpio</i> ) Brain

This study investigates gene expression profiles over time in the brain of juvenile carp subjected to several acute stressors, which have not yet been investigated in such detail in this fish species so far. A stress trial with carp was conducted aiming at identifying relevant differences in gene expressions 30, 60, and 90 min after treatment. Using quantitative real‐time PCR, the expression of hypothalamic–pituitary–interrenal (HPI)‐related axis genes and immediate early genes (IEGs) across four different brain parts (telencephalon, hypothalamus, optic tectum, rhombencephalon). Our findings show that acute stress resulted in pronounced effects on the gene expression patterns in all brain parts between control fish or fish sampled 30, 60, or 90 min after stress application. Furthermore, the gene regulation patterns in feed rewarded and feed control fish frequently show differences to the gene expression patterns of confined and air‐exposed fish. These results provide new insights into the dynamics of stress‐induced gene regulation in fish, emphasizing the complexity and specificity of the HPI axis response to different stressors over time.