| 1. |
- Johansen, I. B., et al.
(författare)
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Bigger is not better: cortisol-induced cardiac growth and dysfunction in salmonids
- 2017
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 220:14, s. 2545-2553
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Tidskriftsartikel (refereegranskat)abstract
- Stress and elevated cortisol levels are associated with pathological heart growth and cardiovascular disease in humans and other mammals. We recently established a link between heritable variation in post-stress cortisol production and cardiac growth in salmonid fish too. A conserved stimulatory effect of the otherwise catabolic steroid hormone cortisol is probably implied, but has to date not been established experimentally. Furthermore, whereas cardiac growth is associated with failure of the mammalian heart, pathological cardiac hypertrophy has not previously been described in fish. Here, we show that rainbow trout (Oncorhynchus mykiss) treated with cortisol in the diet for 45 days have enlarged hearts with lower maximum stroke volume and cardiac output. In accordance with impaired cardiac performance, overall circulatory oxygen-transporting capacity was diminished as indicated by reduced aerobic swimming performance. In contrast to the well-known adaptive/physiological heart growth observed in fish, cortisol-induced growth is maladaptive. Furthermore, the observed heart growth was associated with up-regulated signature genes of mammalian cardiac pathology, suggesting that signalling pathways mediating cortisol-induced cardiac remodelling in fish are conserved from fish to mammals. Altogether, we show that excessive cortisol can induce pathological cardiac remodelling. This is the first study to report and integrate the etiology, physiology and molecular biology of cortisol-induced pathological remodelling in fish.
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| 2. |
- Hoglund, E., et al.
(författare)
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Contrasting Coping Styles Meet the Wall: A Dopamine Driven Dichotomy in Behavior and Cognition
- 2017
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Ingår i: Frontiers in Neuroscience. - : Frontiers Media SA. - 1662-453X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Individual variation in the ability to modify previously learned behavior is an important dimension of trait correlations referred to as coping styles, behavioral syndromes or personality. These trait clusters have been shaped by natural selection, and underlying control mechanisms are often conserved throughout vertebrate evolution. In teleost fishes, behavioral flexibility and coping style have been studied in the high (HR) and low-responsive (LR) rainbow trout lines. Generally, proactive LR trout show a behavior guided by previously learned routines, while HR trout show a more flexible behavior relying on environmental cues. In mammals, routine dependent vs. flexible behavior has been connected to variation in limbic dopamine (DA) signaling. Here, we studied the link between limbic DA signaling and individual variation in flexibility in teleost fishes by a reversal learning approach. HR/LR trout were challenged by blocking a learned escape route, previously available during interaction with a large and aggressive conspecific. LR trout performed a higher number of failed escape attempts against the transparent blockage, while HR trout were more able to inhibit the now futile escape impulse. Regionally discrete changes in DA neurochemistry were observed in micro dissected limbic areas of the telencephalon. Most notably, DA utilization in the dorsomedial telencephalon (DM, a suggested amygdala equivalent) remained stable in HR trout in response to reversal learning under acute stress, while increasing from an initially lower level in LR trout. In summary, these results support the view that limbic homologs control individual differences in behavioral flexibility even in non-mammalian vertebrates.
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| 3. |
- Höglund, Erik, et al.
(författare)
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Dietary L-tryptophan leaves a lasting impression on the brain and the stress response
- 2017
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Ingår i: British Journal of Nutrition. - : Cambridge University Press. - 0007-1145 .- 1475-2662. ; 117:10, s. 1351-1357
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Tidskriftsartikel (refereegranskat)abstract
- Comparative models suggest that effects of dietary tryptophan (Trp) on brain serotonin (5-hydroxytryptamine; 5-HT) neurochemistry and stress responsiveness are present throughout the vertebrate lineage. Moreover, hypothalamic 5-HT seems to play a central role in control of the neuroendocrine stress axis in all vertebrates. Still, recent fish studies suggest long-term effects of dietary Trp on stress responsiveness, which are independent of hypothalamic 5-HT. Here, we investigated if dietary Trp treatment may result in long-lasting effects on stress responsiveness, including changes in plasma cortisol levels and 5-HT neurochemistry in the telencephalon and hypothalamus of Atlantic salmon. Fish were fed diets containing one, two or three times the Trp content in normal feed for 1 week. Subsequently, fish were reintroduced to control feed and were exposed to acute crowding stress for 1 h, 8 and 21 d post Trp treatment. Generally, acute crowding resulted in lower plasma cortisol levels in fish treated with 3xTrp compared with 1xTrp- and 2xTrp-treated fish. The same general pattern was reflected in telencephalic 5-HTergic turnover, for which 3xTrp-treated fish showed decreased values compared with 2xTrp-treated fish. These long-term effects on post-stress plasma cortisol levels and concomitant 5-HT turnover in the telencephalon lends further support to the fact that the extrahypothalamic control of the neuroendocrine stress response is conserved within the vertebrate lineage. Moreover, they indicate that trophic/structural effects in the brain underlie the effects of dietary Trp treatment on stress reactivity.
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| 4. |
- Magnhagen, Carin, et al.
(författare)
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Behavioural responses in a net restraint test predict interrenal reactivity in Arctic charr Salvelinus alpinus
- 2015
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 87:1, s. 88-99
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a 1 min net restraint test was evaluated as a method to predict stress-coping style in Arctic charr Salvelinus alpinus, by investigating the relationship between behaviour during the test and levels of plasma cortisol sampled after 30 min confinement. In two separate groups of S. alpinus, general linearized model revealed significant correlations between cortisol levels and principal component scores extracted from principal component analysis, combining measures of activity in the tests. With the use of glmulti, the model selection ruled out any effects of size, sex and order of capture on interrenal reactivity. In general, S. alpinus that were more active in the net restraint test also had low levels of circulating cortisol, suggesting a proactive coping style. The results from two repeated runs were not correlated, but both runs, performed eight days apart, show a negative correlation between post-stress cortisol level and activity in the net. The lack of consistency could be explained by different treatments before each run and individual differences in behavioural plasticity. The net restraint test is thus predictive of stress-coping style in S. alpinus, and has the benefit of being less time-consuming than the commonly used confinement stress test.
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| 5. |
- Mes, D., et al.
(författare)
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Effects of environmental enrichment on forebrain neural plasticity and survival success of stocked Atlantic salmon
- 2019
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 222:23
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Tidskriftsartikel (refereegranskat)abstract
- Fish reared for stocking programmes are severely stimulus deprived compared with their wild conspecifics raised under natural conditions. This leads to reduced behavioural plasticity and low post-release survival of stocked fish. Environmental enrichment can have positive effects on important life skills, such as predator avoidance and foraging behaviour, but the neural mechanisms underpinning these behavioural changes are still largely unknown. In this study, juvenile Atlantic salmon (Salmo safer) were reared in an enriched hatchery environment for 7 weeks, after which neurobiological characteristics and post-release survival were compared with those of fish reared under normal hatchery conditions. Using in situ hybridization and qPCR, we quantified the expression of brain derived neurotrophic factor (bdnf) and the neural activity marker dos in telencephalic subregions associated with relational memory, emotional learning and stress reactivity. Aside from lower expression of bdnf in the Dlv (a region associated with relational memory) of enriched salmon, we observed no other significant effects of enrichment in the studied regions. Exposure to an enriched environment increased postrelease survival during a 5 month residence in a natural river by 51%. Thus, we demonstrate that environmental enrichment can improve stocking success of Atlantic salmon parr and that environmental enrichment is associated with changes in bdnf expression in the fish's hippocampus-equivalent structure.
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| 6. |
- Mes, D., et al.
(författare)
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Neurobiology of Wild and Hatchery-Reared Atlantic Salmon: How Nurture Drives Neuroplasticity
- 2018
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Ingår i: Frontiers in Behavioral Neuroscience. - 1662-5153. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Life experiences in the rearing environment shape the neural and behavioral plasticity of animals. In fish stocking practices, the hatchery environment is relatively stimulus deprived and does not optimally prepare fish for release into the wild. While the behavioral differences between wild and hatchery-reared fish have been examined to some extent, few studies have compared neurobiological characteristics between wild and hatchery reared individuals. Here, we compare the expression of immediate early gene cfos and neuroplasticity marker brain-derived neurotrophic factor (bdnf) in telencephalic subregions associated with processing of stimuli in wild and hatchery-reared Atlantic salmon at basal and 30 min post (acute) stress conditions. Using in situ hybridization, we found that the expression level of these markers is highly specific per neuronal region and affected by both the origin of the fish, and exposure to acute stress. Expression of dos was increased by stress in all brain regions and cfos was more highly expressed in the Dlv (functional equivalent to the mammalian hippocampus) of hatchery reared compared to wild fish. Expression of bdnf was higher overall in hatchery fish, while acute stress upregulated bdnf in the Dm (functional equivalent to the mammalian amygdala) of wild, but not hatchery individuals. Our findings demonstrate that the hatchery environment affects neuroplasticity and neural activation in brain regions that are important for learning processes and stress reactivity, providing a neuronal foundation for the behavioral differences observed between wild and hatchery-reared fish.
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| 7. |
- Vindas, Marco A., et al.
(författare)
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Early life stress induces long-term changes in limbic areas of a teleost fish: the role of catecholamine systems in stress coping
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Early life stress (ELS) shapes the way individuals cope with future situations. Animals use cognitive flexibility to cope with their ever-changing environment and this is mainly processed in forebrain areas. We investigated the performance of juvenile gilthead seabream, previously subjected to an ELS regime. ELS fish showed overall higher brain catecholaminergic (CA) signalling and lower brain derived neurotrophic factor (bdnf) and higher cfos expression in region-specific areas. All fish showed a normal cortisol and serotonergic response to acute stress. Brain dopaminergic activity and the expression of the alpha(2A) adrenergic receptor were overall higher in the fish homologue to the lateral septum (Vv), suggesting that the Vv is important in CA system regulation. Interestingly, ELS prevented post-acute stress downregulation of the alpha(2A) receptor in the amygdala homologue (Dm3). There was a lack of post-stress response in the beta(2) adrenergic receptor expression and a downregulation in bdnf in the Dm3 of ELS fish, which together indicate an allostatic overload in their stress coping ability. ELS fish showed higher neuronal activity (cfos) post-acute stress in the hippocampus homologue (Dlv) and the Dm3. Our results show clear long-term effects on limbic systems of seabream that may compromise their future coping ability to environmental challenges.
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