title: Social stress modulates the cortisol response to an acute stressor in rainbow trout (Oncorhynchus mykiss).
abstract: In rainbow trout (Oncorhynchus mykiss) of subordinate social status, circulating cortisol concentrations were elevated under resting conditions but the plasma cortisol and glucose responses to an acute stressor (confinement in a net) were attenuated relative to those of dominant trout. An in vitro head kidney preparation, and analysis of the expression of key genes in the stress axis prior to and following confinement in a net were then used to examine the mechanisms underlying suppression of the acute cortisol stress response in trout experiencing chronic social stress. With porcine adrenocorticotropic hormone (ACTH) as the secretagogue, ACTH-stimulated cortisol production was significantly lower for head kidney preparations from subordinate trout than for those from dominant trout. Dominant and subordinate fish did not, however, differ in the relative mRNA abundance of melanocortin-2 receptor (MC2R), steroidogenic acute regulatory protein (StAR) or cytochrome P450 side chain cleavage enzyme (P450scc) within the head kidney, although the relative mRNA abundance of these genes was significantly higher in both dominant and subordinate fish than in sham trout (trout that did not experience social interactions but were otherwise treated identically to the dominant and subordinate fish). The relative mRNA abundance of all three genes was significantly higher in trout exposed to an acute net stressor than under control conditions. Upstream of cortisol production in the stress axis, plasma ACTH concentrations were not affected by social stress, nor was the relative mRNA abundance of the binding protein for corticotropin releasing factor (CRF-BP). The relative mRNA abundance of CRF in the pre-optic area of subordinate fish was significantly higher than that of dominant or sham fish 1h after exposure to the stressor. Collectively, the results indicate that chronic social stress modulates cortisol production at the level of the interrenal cells, resulting in an attenuated cortisol response to an acute stressor.
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, ON, Canada.
authors.forename: J D
authors.initials: JD
authors.lastname: Jeffrey
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, ON, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Gollock
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, ON, Canada. Electronic address: kgilmour@uottawa.ca.
authors.forename: K M
authors.initials: KM
authors.lastname: Gilmour
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D029941:Fish Proteins / Q000235:genetics; D060226:Head Kidney / Q000187:drug effects / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects; D017686:Oncorhynchus mykiss / Q000502:physiology*; D012931:Social Environment; D013315:Stress, Psychological / Q000097:blood*; D013552:Swine
chemical_list: D029941:Fish Proteins; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone
keywords: 3′-5′-cyclic adenosine monophosphate; ACTH; ANOVA; Adrenocorticotropic hormone; BSA; CRF; CRF-BP; Cortisol; DEPC; EDTA; HPA; HPI; HPI axis; Interrenal cells; L:D; MC2R; MEM; P450scc; PKA; POA; RM ANOVA; RT-PCR; Rainbow trout; SEM; Social stress; StAR; adrenocorticotropic hormone; analysis of variance; bovine serum albumin; cAMP; cDNA; complementary deoxyribonucleic acid; corticotropin-releasing factor; corticotropin-releasing factor-binding protein; cytochrome P450 side chain cleavage enzyme; diethylpyrocarbonate; ethylenediaminetetraacetic acid; hypothalamic–pituitary–adrenal; hypothalamic–pituitary–interrenal; light:dark; mRNA; melanocortin 2 receptor; messenger ribonucleic acid; minimum essential medium; preoptic area; protein kinase A; repeated measures ANOVA; reverse transcription-polymerase chain reaction; standard error of the mean; steroidogenic acute regulatory protein