| 1. |
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| 2. |
- Backström, Tobias, et al.
(författare)
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Stress effects on AVT and CRF systems in two strains of rainbow trout (Oncorhynchus mykiss) divergent in stress responsiveness
- 2011
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Ingår i: Hormones and Behavior. - : Elsevier BV. - 0018-506X .- 1095-6867. ; 59:1, s. 180-186
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Tidskriftsartikel (refereegranskat)abstract
- The aim for this study was to examine whether the F4 generation of two strains of rainbow trout divergent in their plasma cortisol response to confinement stress (HR: high responder or LR: low responder) would also differ in stress-induced effects on forebrain concentrations of mRNA for corticotropin-releasing factor (CRF). arginine vasotocin (AVT). CRF receptor type 1 (CRF-R1). CRF receptor type 2 (CRF-R2) and AVT receptor (AVT-R). In addition, plasma cortisol concentrations, brainstem levels of monoamines and monoamine metabolites, and behaviour during confinement were monitored. The results confirm that HR and LR trout differ in their cortisol response to confinement and show that fish of these strains also differ in their behavioural response to confinement. The HR trout displayed significantly higher locomotor activity while in confinement than LR trout. Moreover, following 180 min of confinement HR fish showed significantly higher forebrain concentrations of CRF mRNA than LR fish. Also, when subjected to 30 min of confinement HR fish showed significantly lower CRF-R2 mRNA concentrations than LR fish, whereas there were no differences in CRF-R1. AVT or AVT-R mRNA expression between LR and HR fish either at 30 or 180 min of confinement. Differences in the expression of CRF and CRF-R2 mRNA may be related to the divergence in stress coping displayed by these rainbow trout strains.
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| 3. |
- Basic, Dean, et al.
(författare)
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Changes in regional brain monoaminergic activity and temporary down-regulation in stress response from dietary supplementation with L-tryptophan in Atlantic cod (Gadus morhua)
- 2013
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Ingår i: British Journal of Nutrition. - 0007-1145 .- 1475-2662. ; 109:12, s. 2166-2174
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Tidskriftsartikel (refereegranskat)abstract
- The brain monoamines serotonin (5-hydroxytryptamine; 5-HT) and dopamine (DA) both play an integrative role in behavioural and neuroendocrine responses to challenges, and comparative models suggest common mechanisms for dietary modulation of transmission by these signal substances in vertebrates. Previous studies in teleosts demonstrate that 7 d of dietary administration with L-tryptophan (Trp), the direct precursor of 5-HT, suppresses the endocrine stress response. The present study investigated how long the suppressive effects of a Trp-enriched feed regimen, at doses corresponding to two, three or four times the Trp levels in commercial feed, last in juvenile Atlantic cod (Gadus morhua) when the fish are reintroduced to a diet with standard amino acid composition. We also wanted to determine whether Trp supplementation induced changes in brain monoaminergic neurochemistry in those forebrain structures innervated by DA- and 5-HTergic neurons, by measuring regional activity of DA and 5-HT in the lateral pallial regions (Dl) of the telencephalon and nucleus lateralis tuberis (NLT) of the hypothalamus. Dietary Trp resulted in a dose-dependent suppression in plasma cortisol among fish exposed to confinement stress on the first day following experimental diet; however, such an effect was not observed at 2 or 6 d after Trp treatment. Feeding the fish with moderate Trp doses also evoked a general increase in DA and 5-HT-ergic activity, suggesting that these neural circuits within the NLT and Dl may be indirectly involved in regulating the acute stress response.
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| 4. |
- Basic, Dean, et al.
(författare)
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Short- and long-term effects of dietary L-tryptophan supplementation on the neuroendocrine stress response in seawater-reared Atlantic salmon (Salmo salar)
- 2013
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 388, s. 8-13
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Tidskriftsartikel (refereegranskat)abstract
- The essential amino acid L-tryptophan (Trp) is the immediate precursor of the neurotransmitter serotonin (5-HT). Supplementing Trp through diet has been shown to suppress the neuroendocrine stress response in vertebrates including teleosts. In salmonid fish, adjusting to the social environment as well as habituation to seawater involves the neuroendocrine stress response, suggesting that such environmental factors may modulate the stress-reducing effects of Trp. To date, studies that have investigated the neuroendocrine effects of dietary Trp have only been conducted in rainbow trout (Oncorhynchus mykiss), a salmonid species, under conditions featuring social isolation in the freshwater environment. Here, we address the effects of dietary Trp on post-stress plasma cortisol and hypothalamic monoamines in seawater-adapted Atlantic salmon (Salmo salar), reared at densities relevant for aquaculture. Fish were given feed containing 1, 2, 3 or 4 times the Trp content in normal feed for one week. Subsequently, the fish were reintroduced to feed containing the lowest Trp level, corresponding to standard commercial feed for a number of days prior to exposure to an acute confinement stressor. Basal plasma cortisol levels were lower among non-stressed fish at 1 and 10 days post dietary Trp supplementation. By comparison, stressed fish displayed stimulatory post-stress plasma cortisol responses at 1 and 2 days after the Trp regimen was terminated. However, a reversed pattern was observed among these fish at 10 days after Trp treatment. The overall effects of dietary Trp were more pronounced in dopamine (DA) neurochemistry compared to 5-HT in the hypothalamus. The results demonstrate both short-and long-term effects of elevated dietary Trp on the neuroendocrine stress response. These findings suggest that hypothalamic DA may be more involved than 5-HT in the stress reducing effects of Trp in seawater-adapted Atlantic salmon, reared at densities relevant for aquaculture.
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| 5. |
- Höglund, Erik, et al.
(författare)
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Avoidance behavior and brain monoamines in fish
- 2005
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Ingår i: BRAIN RESEARCH. ; 1032:1-2, s. 104-110
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Tidskriftsartikel (refereegranskat)abstract
- The crucian carp performs a typical avoidance behavior when exposed to olfactory cues from injured skin of conspecifics. They swim rapidly to the bottom and hide in available material. This work examines the effects of skin extract exposure and availability of hiding material on this behavior, and concomitant changes in brain monoaminergic activity in crucian carp. Individual fish were exposed to skin extract in aquaria with or without hiding material. Exposure to skin extract resulted in the expected avoidance behavior consisting of rapid movement towards the bottom of the aquarium. This lasted for 1-2 min. Activity then decreased below the level observed before exposure, suggesting a "freezing" type of avoidance behavior. This behavior was independent of availability of hiding material.Brain dopaminergic activity increased in telencephalon and decreased in the brain stem following skin extract exposure, again independent of availability of hiding material. However, fish kept in aquaria without hiding material showed an elevation of serotonergic activity in the brain stem and the optic tectum compared to fish with available hiding material. Absence of hiding material increased serotonergic activity also without exposure to skin extract. In aquaria with hiding material, the fish stirred up a cloud of fine sediments and showed a more pronounced decrease in locomotor activity in agreement with this being a more efficient freezing or immobile avoidance behavior. These results show that basic components of avoidance behavior and related brain changes are present in the fish brain, in accordance with the common phylogenetic roots of avoidance behavior in all vertebrates. (C) 2004 Elsevier B.V. All rights reserved.
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| 6. |
- 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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| 7. |
- Joachim, Schjolden, et al.
(författare)
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Does individual variation in stress responses and agonistic behavior reflect divergent stress coping strategies in juvenile rainbow trout?
- 2005
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Ingår i: PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY. ; 78:5, s. 715-723
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Individual rainbow trout were transferred to visual isolation in experimental aquaria. As a measure of the speed of acclimation, individual food intake was quantified during the first 6 d following transfer. Following acclimation, aggression was quantified by subjecting the fish to three resident-intruder tests, with 30 d of recovery between the tests. Moreover, between the resident-intruder tests (i.e., two times) the fish were exposed to an unfamiliar environment and their cortisol response was measured. The results of this study show that individuals of juvenile rainbow trout differ distinctly in their response to changes in their environment, and that this diversity in behavior is reflected by consistent behavioral traits displayed by individual fish. These traits have proven to be consistent not only over time but also across situations, revealing two distinct behavioral profiles, in the same manner as shown in studies on proactive and reactive mammals. Our results also show that the reactivity of the hypothalamic-pituitary-interrenal (HPI) axis, when exposed to a stressor, is a consistent physiological trait in juvenile rainbow trout. We found that difference in HPI axis reactivity is linked to the different behavioral profiles. However, HPI axis reactivity could not be linked directly to the singular behavioral traits measured. In other words, we did not find that the consistent behavioral traits shown by the fish were associated with a difference in HPI axis reactivity in the same manner as the reactivity of the hypothalamic-pituitary-adrenocortical axis does in mammals. Taken together, our results show that stress coping strategies akin to what has been described as reactive and proactive stress coping in mammals appear to exist in juvenile rainbow trout.
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| 8. |
- Schjolden, Joachim, et al.
(författare)
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Aggression in rainbow trout is inhibited by both MR and GR antagonists
- 2009
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Ingår i: Physiology and Behavior. - : Elsevier BV. - 0031-9384 .- 1873-507X. ; 98:5, s. 625-630
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: The present study has investigated the effect of exogenous cortisol on aggression in juvenile rainbow trout, along with the involvement of mineralocorticoid (MR) and glucocorticoid receptors (GR) mediating the effects of cortisol. Fish were fed pellets supplemented with cortisol, the GR antagonist mifepristone (RU486) in combination with cortisol, the MR antagonist spironolactone (SA) in combination with cortisol or both antagonists in combination with cortisol. Aggressive behaviour was then assessed I h subsequent to feeding. Our results showed that the attack latency was increased by exogenous cortisol, an effect that was not abolished by the antagonists. The intensity of aggression was not changed by exogenous cortisol. However, the intensity of aggression was significantly reduced by both antagonists. These results are discussed with regard to cortisol affecting aggressive behaviour through genomic and non-genomic pathways. Our results have demonstrated the involvement of both MR and GR in regulating behavioural responses during social interactions in teleost fish. The intensity of aggression seen in control and cortisol treated fish is probably mediated by the basal levels of cortisol through the intracellular MRs and GRs. We conclude that the initiative to engage in social confrontations is mediated through a non-genomic pathway, which could involve extracellular corticoid receptors. Further, the majority of arguments lean towards the MR and GR antagonists blocking the effect of cortisol on aggressive intensity through intracellular receptors. If this is the case, then it is probable that these two aspects of aggressive behaviour are based on different neuronal mechanisms.
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| 9. |
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| 10. |
- Schjolden, Joachim, et al.
(författare)
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Divergence in behavioural responses to stress in two strains of rainbow trout (Oncorhynchus mykiss) with contrasting stress responsiveness
- 2005
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Ingår i: Hormones and Behavior. - : Elsevier BV. - 0018-506X .- 1095-6867. ; 48:5, s. 537-544
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to establish whether two lines of rainbow trout divergent for their plasma cortisol response to a standardized stressor would show consistent differences in their behavioural response to a range of challenging situations. Our results show that the high- and low-responding (HR and LR) lines of rainbow trout did not differ in the aggression shown towards an intruder or in their response to the introduction of a novel object to their home environment. However, there was a difference in behaviour between the two selection lines when they were exposed to two unfamiliar environments. These results suggest that the behaviour of the HR and LR fish differs when they are challenged in unfamiliar environments, while their behaviour does not differ when they are challenged in their home environment. These observations are in agreement with studies on mammals that show that individuals with reactive coping styles perform similarly to proactive animals when they are challenged in a familiar environment, while they show different behaviour when they are challenged in unfamiliar environments. Thus, these results provide further evidence that the HR and LR selection lines of rainbow trout exemplify the two different coping styles described in mammals.
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| 11. |
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| 12. |
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| 13. |
- Schjolden, Joachim, et al.
(författare)
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Genetically determined variation in stress responsiveness in rainbow trout : behavior and neurobiology
- 2007
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Ingår i: Brain, behavior, and evolution. - : S. Karger AG. - 0006-8977 .- 1421-9743. ; 70:4, s. 227-238
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Tidskriftsartikel (refereegranskat)abstract
- It is becoming increasingly recognized that the diversity in stressors, their intensity, predictability and the context in which they are experienced, will result in behavioral and physiological responses just as diverse. In addition, stress responses are characterized by individual variations where the physiological and behavioral reactions are associated in such a manner that distinct stress coping styles encompassing suites of correlated traits can be identified. These are often referred to as proactive and reactive stress coping styles. Proactive coping is characterized by more aggression, higher general activity and higher sympathetic activation, whereas reactive coping is characterized by immobility, lack of initiative and a higher parasympathetic/hypothalamic activation. Stable coping styles appear to coexist within populations, and these strategies appear to be largely innate. Moreover, the physiological and behavioral traits of coping styles appear to be heritable. These stress coping styles have proven to play a major role in competitive ability and subsequent social position in different species of vertebrates. However, there are also studies showing that social position can affect parameters encompassing the stress coping style of individuals. In this regard it is important, but not always easy, to distinguish between causes and effects of behavioral and physiological responses to stressors. The question raised is to what extent and rigidness stress coping styles are guided by genetic factors.
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| 14. |
- Schjolden, Joachim, et al.
(författare)
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Melanocortin peptides affect the motivation to feed in rainbow trout (Oncorhynchus mykiss)
- 2009
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Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 160:2, s. 134-138
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigated the effects of one melanocortin receptor (MCR) agonist and two antagonists on food intake in juvenile rainbow trout. Baseline food intake was established prior to 1 microl intracerebroventricular injection (ICV) of the non-specific agonist MTII, the MC4R antagonist HS024 and the MC3/4R antagonist SHU9119 at concentrations of 0.3, 1 or 3 nM. Saline-injected fish and untreated fish served as controls. Changes in food intake were observed 1h after the ICV injections. Our results showed that treatment with MTII significantly decreased food intake at 3 nM compared to control, HS024 significantly increased food intake at 3 nM compared to control and saline-treated fish, and SHU9119 significantly increased food intake at 3 nM compared to saline-treated fish. In conclusion, our study provides further evidence, and hence strengthens the hypothesis, that MC4R participates in the control of energy balance in fish in the same manner as in mammals. Our findings that HS024 is more potent than SHU9119 in increasing food intake suggest that the effects of melanocortin on energy balance in rainbow trout are mainly regulated by activation of MC4R. Hence, HS024 seems an excellent tool as a MC4R antagonist in rainbow trout.
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| 15. |
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| 16. |
- Schjolden, Joachim, et al.
(författare)
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Serotonergic characteristics of rainbow trout divergent in stress responsiveness
- 2006
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Ingår i: PHYSIOLOGY & BEHAVIOR. - 0031-9384. ; 87:5, s. 938-947
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Juvenile rainbow trout divergent in their cortisol response to confinement stress (HR: high responsive or LR: low responsive fish) were exposed to either I or 3 h of confinement stress. Untreated fish served as control. After the exposure blood and brain samples were collected. From the blood samples, the levels of cortisol and catecholamines were determined, while the brain serotonergic and monoamineoxidase (MAO) activity was determined in four different brain areas (brain stem, hypothalamus, telencephalon and optic rectum). Our results show that the LR fish responds to handling stress with a higher increase in plasma epinephrine compared to HR fish. Our results also show that confinement stress leads to a larger increase in the serotonergic activity in the brain stem and telencephalon in LR fish compared to HR fish. These results support the hypothesis that stress coping strategies similar to those described in mammals also exists in fish. Further, our results have shown that the MAO activity increases in optic tectum and hypothalamus of rainbow trout during confinement stress, while it remains unchanged or decreases in brain stem and telencephalon. Moreover, the MAO activity does not differ between the two selection lines. This indicates that MAO participates actively in the stress response without contributing to the differences in stress coping strategies. (c) 2006 Elsevier Inc. All rights reserved.
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| 17. |
- Schjolden, Joachim, 1971-
(författare)
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Stress Coping Strategies in Rainbow Trout (Oncorhynchus mykiss)
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Animals show a great variety in physiological and behavioural responses to stressors. These responses are often bimodally distributed within populations and show consistency on an individual level over time and across situations, which in terrestrial vertebrates have been identified as proactive and reactive stress coping strategies. Proactive animals show lower cortisol responses, higher sympathetic activation and brain serotonergic activity compared to reactive animals. Behaviourally, proactive animals are more aggressive, more active in avoiding stressors, they form routines and show fewer cases of conditioned immobility compared to reactive animals. Our aim has been to reveal if such stress coping strategies exist in fish. Our results show that rainbow trout with high (HR) or low (LR) cortisol responses to stressors differs in sympathetic activation and brain serotonin turnover in the same manner as proactive and reactive mammals. HR fish showed less locomotor activity when reared in large groups (30 individuals) compared to LR fish. When reared in isolation there were no differences between HR and LR fish when exposed to stressors within a familiar environment. The adaption of a proactive coping style among reactive coping individuals when they are challenged within a familiar environment has previously been shown to be distinction between proactive and reactive coping mammals. However, when they were transferred to unfamiliar environments a behavioural difference between the two lines was observed indicating different stress coping strategies akin to those described in mammals. Finally, we observed a consistency over time in the cortisol response of an unselected line of rainbow trout. Fish from this line also demonstrated a correlation between behavioural responses to different stressors. However, there was no apparent connection between these behavioural responses and the cortisol response. Overall, the results of this thesis have strengthened the hypothesis that different stress coping strategies exist in teleost fish.
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