Fig. 1.

Graphical description of the differences and similarities in the tissues and signaling pathways in the stress response between fish and mammalian models. When stress is perceived by sensory cells in both fish and mammals, the signal is sent to the hypothalamus, which then releases corticotropin releasing hormone (CRH), the first major signaling hormone in this pathway. When CRH is detected by receptors in the pituitary, adrenocorticotropic hormone (ACTH) and α-Melanocyte-stimulating hormone (α-MSH) are released. The pituitary also releases growth hormones (GH) and prolactin (PRL). Additionally, ACTH stimulates the release of cortisol in the inter-renal cells of the fish head kidney, and the adrenal cortex of the mammalian adrenal gland. Alternatively, catecholamines are produced by the chromaffin cells of the fish head kidney and the adrenal medulla of the mammalian adrenal gland, the release of which is caused by signaling via acetylcholine (Ach). Superscripted values indicate the respective receptor type(s) for each hormone. The described hormones are, CRH-receptor (CRH-R), melanocortin 2 receptor (MC2R), melanocortin receptor (MCR), GH-receptor (GH-R), PRL-receptor (PRL-R), glucocorticoid receptor (GR), mineralocorticoid receptor (MR), α adrenergic receptors (α-AR), β adrenergic receptors (β-AR). Some receptor notations were generalized due to the lack of standardized notation between different fish species.