title: A comparative study of the response to repeated chasing stress in Atlantic salmon (Salmo salar L.) parr and post-smolts.
abstract: When Atlantic salmon parr migrate from fresh water towards the sea, they undergo extensive morphological, neural, physiological and behavioural changes. Such changes have the potential to affect their responsiveness to various environmental factors that impose stress. In this study we compared the stress responses in parr and post-smolt salmon following exposure to repeated chasing stress (RCS) for three weeks. At the end of this period, all fish were challenged with a novel stressor and sampled before (T0) and after 1h (T1). Parr had a higher growth rate than post-smolts. Plasma cortisol declined in the RCS groups within the first week suggesting a rapid habituation/desensitisation of the endocrine stress axis. As a result of the desensitised HPI axis, RCS groups showed a reduced cortisol response when exposed to the novel stressor. In preoptic area (POA) crf mRNA levels were higher in all post-smolt groups compared to parr. 11βhsd2 decreased by RCS and by the novel stressor in post-smolt controls (T1), whereas no effect of either stress was seen in parr. The grs were low in all groups except for parr controls. In pituitary, parr controls had higher levels of crf1r mRNA than the other parr and post-smolt groups, whilst pomcb was higher in post-smolt control groups. Overall, 11βhsd2 transcript abundance in parr was lower than post-smolt groups; after the novel stressor pomcs, grs and mr were up-regulated in parr control (T1). In summary, we highlight differences in the central stress response between parr and post-smolt salmon following RCS.
authors.affiliation: Institute of Marine Research, NO-5984 Atredal, Norway. Electronic address: angelico.madaro@imr.no.
authors.forename: Angelico
authors.initials: A
authors.lastname: Madaro
authors.affiliation: Institute of Marine Research, NO-5984 Atredal, Norway; Norwegian University of Science and Technology, Department of Biology, 7491 Trondheim, Norway.
authors.forename: Rolf Erik
authors.initials: RE
authors.lastname: Olsen
authors.affiliation: Institute of Marine Research, NO-5984 Atredal, Norway.
authors.forename: Tore S
authors.initials: TS
authors.lastname: Kristiansen
authors.affiliation: Uni Research AS, Department of Integrative Fish Biology, N-5006 Bergen, Norway.
authors.forename: Lars O E
authors.initials: LO
authors.lastname: Ebbesson
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, 6525 AJ Nijmegen, 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, 6525 AJ Nijmegen, The Netherlands.
authors.forename: Marnix
authors.initials: M
authors.lastname: Gorissen
mesh_terms: D000818:Animals; D004924:Escape Reaction / Q000502:physiology*; D005618:Fresh Water; D005786:Gene Expression Regulation; D006854:Hydrocortisone / Q000097:blood; D008018:Life Cycle Stages / Q000502:physiology*; D011235:Predatory Behavior / Q000502:physiology; D011301:Preoptic Area / Q000378:metabolism; D020317:Salmo salar / Q000097:blood / Q000254:growth & development / Q000502:physiology*; D012623:Seawater; D013312:Stress, Physiological / Q000235:genetics / Q000502:physiology*; D013315:Stress, Psychological / Q000097:blood / Q000235:genetics
chemical_list: D006854:Hydrocortisone
keywords: Allostasis; Brain; Cortisol; Gene expression; HPI-axis; Pituitary gland; Salmo salar