title: Stress in Atlantic salmon: response to unpredictable chronic stress.
abstract: Combinations of stressors occur regularly throughout an animal's life, especially in agriculture and aquaculture settings. If an animal fails to acclimate to these stressors, stress becomes chronic, and a condition of allostatic overload arises with negative results for animal welfare. In the current study, we describe effects of exposing Atlantic salmon parr to an unpredictable chronic stressor (UCS) paradigm for 3 weeks. The paradigm involves exposure of fish to seven unpredictable stressors three times a day. At the end of the trial, experimental and control fish were challenged with yet another novel stressor and sampled before and 1 h after that challenge. Plasma cortisol decreased steadily over time in stressed fish, indicative of exhaustion of the endocrine stress axis. This was confirmed by a lower cortisol response to the novel stressor at the end of the stress period in chronically stressed fish compared with the control group. In the preoptic area (POA) and pituitary gland, chronic stress resulted in decreased gene expression of 11βhsd2, gr1 and gr2 in the POA and increased expression of those genes in the pituitary gland. POA crf expression and pituitary expression of pomcs and mr increased, whereas interrenal gene expression was unaffected. Exposure to the novel stressor had no effect on POA and interrenal gene expression. In the pituitary, crfr1, pomcs, 11βhsd2, grs and mr were down-regulated. In summary, our results provide a novel overview of the dynamic changes that occur at every level of the hypothalamic-pituitary gland-interrenal gland (HPI) axis as a result of chronic stress in Atlantic salmon.
authors.affiliation: Institute of Marine Research, Animal Welfare Science Group, Matredal NO-5984, Norway angelico.madaro@imr.no.
authors.forename: Angelico
authors.initials: A
authors.lastname: Madaro
authors.affiliation: Institute of Marine Research, Animal Welfare Science Group, Matredal NO-5984, Norway Norwegian University of Science and Technology, Department of Biology, Trondheim 7491, Norway.
authors.forename: Rolf E
authors.initials: RE
authors.lastname: Olsen
authors.affiliation: Institute of Marine Research, Animal Welfare Science Group, Matredal NO-5984, Norway.
authors.forename: Tore S
authors.initials: TS
authors.lastname: Kristiansen
authors.affiliation: Uni Research AS, Department of Integrative Fish Biology, Bergen N-5006, Norway.
authors.forename: Lars O E
authors.initials: LO
authors.lastname: Ebbesson
authors.affiliation: Uni Research AS, Department of Integrative Fish Biology, Bergen N-5006, Norway.
authors.forename: Tom O
authors.initials: TO
authors.lastname: Nilsen
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, AJ Nijmegen 6525, The Netherlands.
authors.forename: Gert
authors.initials: G
authors.lastname: Flik
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, AJ Nijmegen 6525, The Netherlands.
authors.forename: Marnix
authors.initials: M
authors.lastname: Gorissen
mesh_terms: D052636:Allostasis; D000818:Animals; D004702:Endocrine Glands / Q000378:metabolism; D005398:Fisheries; D015870:Gene Expression; D006854:Hydrocortisone / Q000097:blood; D007401:Interrenal Gland / Q000502:physiology; D010902:Pituitary Gland / Q000378:metabolism; D011301:Preoptic Area / Q000502:physiology; D020317:Salmo salar / Q000254:growth & development / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D006854:Hydrocortisone
keywords: Brain; Cortisol; Gene study; HPI axis; Head kidney; Hypothalamus; Parr; Pituitary gland; Salmo salar; crf