Changes in regional brain monoaminergic activity and temporary down-regulation in stress response from dietary supplementation with L-tryptophan in Atlantic cod (Gadus morhua)

• Published in: British Journal of Nutrition
• Main Authors: Basic, Dean, Schjolden, Joachim, Krogdahl, Ashild, von Krogh, Kristine, Hillestad, Marie, Winberg, Svante, Mayer, Ian, Skjerve, Eystein, Hoglund, Erik
• Format: Article in Journal/Newspaper
• Language: English
• Published: Uppsala universitet, Fysiologi 2013
• Subjects: Tryptophan; Atlantic cod; Stress response; Nucleus lateralis tuberis; Lateral pallial telencephalon; Medical and Health Sciences; Medicin och hälsovetenskap; atlantic cod; Gadus morhua
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-203263; https://doi.org/10.1017/S0007114512004345

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.