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- Lepage, Olivier, 1974-
(författare)
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Dietary L-Tryptophan Suppresses Aggression and Stress Responsiveness in Juvenile Rainbow Trout (Oncorhynchus mykiss) : The Role of Brain Serotonin and Plasma Melatonin
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Juvenile rainbow trout (Oncorhynchus mykiss) fed L-tryptophan (TRP) supplemented feed for 7 days show a suppression of aggressive behaviour along with a reduction in post-stress plasma cortisol levels. However, 3 days of elevated dietary TRP does not have any effects on either aggressive behaviour or post-stress plasma cortisol levels. The effects of TRP on aggression and stress responsiveness could be related to elevated brain serotonergic activity, TRP being the precursor of serotonin (5-HT). However, 5-HT is, in turn, the precursor of melatonin (ME) and we found that elevated dietary intake of TRP results in an increase in daytime plasma levels of ME. Elevated plasma ME concentrations in rainbow trout fed TRP supplemented feed appear to be of gastrointestinal origin. ME has been suggested to have inhibitory effects on aggressive behaviour and to act as a glucocorticoid antisecretagogue. However, we found that exogenuos ME did not affect aggressive behaviour or post-stress plasma cortisol in rainbow trout. Instead, the effects of TRP on aggressive behaviour and plasma cortisol were mimicked by treatment with the selective serotonin re-uptake inhibitor, citalopram, suggesting that the effects of TRP are mediated by a stimulation of brain 5-HT activity and not by increased ME synthesis and secretion. However, the slow time-course of the effects of TRP on aggressive behaviour and plasma cortisol suggests that effects on 5-HT receptors mechanism are likely to be involved.
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| 5. |
- Lepage, Olivier, et al.
(författare)
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Serotonin, but not melatonin, plays a role in shaping dorninant-subordinate relationships and aggression in rainbow trout
- 2005
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Ingår i: HORMONES AND BEHAVIOR. ; 48:2, s. 233-242
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to clarify to what extent the effects of elevated dietary L-tryptophan (Trp) on aggressive behavior and stress responsiveness in rainbow trout are mediated by circulating melatonin and central serotonin (5-HT), respectively. Isolated rainbow trout were paired for I It a day for 7 days in order to create fish with experience of being dominant and subordinate. Following this week, the fish were tested for aggressive behavior using a resident-intruder test after which they were subjected to one of four treatments: (1) tryptophan, (2) the selective serotonin reuptake inhibitor (SSRI) citalopram, (3) melatonin, and (4) no treatment (controls). After 7 days of treatment, the fish were subjected to a second resident-intruder test. Trp-supplemented feed resulted in a suppression of aggressive behavior in fish with experience of being dominant. Moreover, fish fed Trp-supplemented feed, regardless of social experience, also displayed lower plasma cortisol levels than controls. These effects of elevated dietary Trp were closely mimicked by citalopram treatment, whereas exogenous melatonin had no effect on either aggressive behavior or plasma cortisol. Thus, the effect of elevated dietary Trp on aggressive behavior and stress responses does not appear to be mediated by melatonin even though elevated dietary intake of Trp resulted in an increase in plasma melatonin concentrations.
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| 8. |
- Lepage, Olivier, et al.
(författare)
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Tryptophan affects both gastrointestinal melatonin production and interrenal activity in stressed and nonstressed rainbow trout
- 2005
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Ingår i: Tryptophan affects both gastrointestinal melatonin production and interrenal activity in stressed and nonstressed rainbow trout. ; 38:4, s. 264-271
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Tidskriftsartikel (refereegranskat)abstract
- The present experiments were designed to test the hypothesis that elevated dietary levels of l-tryptophan (Trp) result in elevated plasma levels of melatonin and that this increase in plasma melatonin concentration is caused by elevated melatonin production and secretion by the gastro-intestinal-tract (GIT). Feeding juvenile rainbow trout (Oncorhynchus mykiss) Trp-supplemented feed for 7 days resulted in elevated daytime plasma levels of melatonin and reduced poststress plasma cortisol concentrations. Nighttime plasma melatonin concentrations were, however, not affected by elevated dietary Trp. Moreover, stress caused a reduction in daytime plasma levels of melatonin in fish fed Trp-supplemented feed, an effect that was counteracted by treatment with an alpha-receptor antagonist. These results clearly suggest that elevated dietary intake of Trp results in an increase in the GIT production of melatonin in rainbow trout. A suggestion that was further supported by the results from an in vitro experiment demonstrating that addition of Trp to the incubation medium stimulates melatonin production and release by incubated rainbow trout GIT. The results from this study led us to suggest a possible mechanism for melatonin in mediating the effects of elevated dietary Trp on poststress plasma cortisol concentrations and aggressive behavior in rainbow trout.
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| 9. |
- Sloman, Kathrine A, et al.
(författare)
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Does pulsatile urea excretion serve as a social signal in the gulf toadfish Opsanus beta?
- 2005
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Ingår i: PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY. ; 78:5, s. 724-735
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluated the hypothesis that the pulsatile excretion of urea by toadfish could serve as a social signal. In the first experiment, physiological parameters were measured in pairs of dominant and subordinate toadfish. Subordinate toadfish had elevated concentrations of circulating plasma cortisol, an effect maintained even after cannulation. In the second experiment, one fish of a pair was injected with C-14-urea, and the occurrence of urea pulses during social encounters was documented. Social status did not influence the order of pulsing, that is, whether a dominant or subordinate fish pulsed first during a social encounter. However, in seven out of eight pairs, both toadfish pulsed within 2 h of each other, indicating some form of communication between fish. In the third and final experiment, the response of toadfish to urea (natural or synthetic) was observed. There was a tendency for toadfish to avoid synthetic urea but there was no apparent behavioural response to water containing toadfish urea. Pulsing events do not appear to play an integral role during social encounters as previously hypothesised, but the close timing of pulses in toadfish pairs suggests some transfer of information.
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| 10. |
- Sloman, Kathrine A, et al.
(författare)
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Socially-mediated differences in brain monoamines in rainbow trout: effects of trace metal contaminants
- 2005
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Ingår i: AQUATIC TOXICOLOGY. ; 71:3, s. 237-247
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Tidskriftsartikel (refereegranskat)abstract
- Monoaminergic systems play a crucial role in linking behaviour and physiology. Here the physiological and behavioural effects of metal exposure in relation to monoaminergic systems were considered by exposing rainbow trout dyads, demonstrating stable dominance relationships, to cadmium or lead. Fish exposed to 4 mug l(-1) cadmium accumulated more cadmium at the gill than fish held in control water. Fish exposed to 7 mug l(-1) cadmium had higher gill, liver and kidney cadmium concentrations. No significant lead accumulation was seen after exposure to 46 mug l(-1) for 48 h but exposure to 325 mug l(-1) lead caused an increase in gill, liver and kidney lead concentrations. Brain accumulation of both cadmium and lead was only seen after exposure to the highest concentrations. Exposure to 4 or 7 mug l(-1) cadmium, or 46 or 325 mug l(-1) lead for 48 h did not disrupt established dominance hierarchies. As expected with this stable behavioural situation, in control pairs, animals of different social status displayed different physiological profiles. Subordinate fish had higher concentrations of circulating plasma cortisol and telencephalic 5-hydroxyindoleacetic acid/5-hydroxytryptamine (serotonin) (5-HIAA/5-HT) ratios. However, these physiological profiles were affected by metal exposure, with a trend towards higher serotonergic activity in dominant fish. Dominants exposed to 325 mug l(-1) lead had significantly higher hypothalamic 5-HIAA/5-HT ratios when compared with subordinates. The results demonstrate that if stable social hierarchies are established in control water they may not be affected by exposure to cadmium and lead although physiological changes may be evident.
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| 11. |
- Sodergren, Erica, et al.
(författare)
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The genome of the sea urchin Strongylocentrotus purpuratus.
- 2006
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 314:5801, s. 941-52
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Tidskriftsartikel (refereegranskat)abstract
- We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.
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