IBBEA   24401
INSTITUTO DE BIODIVERSIDAD Y BIOLOGIA EXPERIMENTAL Y APLICADA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
L-Tryptophan supplemented diet increases serotoninergic activity and reduces stress: role of brain serotonin in two South American cichlid fish.
Autor/es:
MORANDINI LEONEL; RAMALLO MARTIN; GUIMARAES MOREIRA R; SOMOZA GUSTAVO; PANDOLFI MATIAS
Reunión:
Congreso; 10th International Symposium on Reproductive Physiology of Fish; 2014
Resumen:
Introduction Recent studies have been focused on the lessening effect over aggression and stress of an enhanced serotonergic activity, by means of L-tryptophan (Trp) supplemented diets. These factors are detrimental to farming of comestible and ornamental fish, particularly in highly aggressive and densely reared species. Cichlasoma dimerus (Cd) and Australoheros facetus (Af) are South American cichlids easy to maintain and breed under laboratory conditions, and exhibit salient social hierarchies with agonistic interactions. Thus, they arise as excellent models to evaluate preliminary serotonin (5-HT) effects. Our first objective was to perform a morphological characterization of the brain serotonergic system in Cd and Af. Secondly, this study aimed to investigate if a Trp enriched diet could affect brain monoamine (5-HT and dopamine) levels, stress and sex hormones and growth in both species. Methods The distribution of 5-HT cell bodies and fibers was described by means of an immunofluorescence technique using anti-5-HT antibodies. Experiments were performed with fish held in separated aquaria (21 L) for 35 days. During the first week (acclimation period) animals were fed with a control diet (no added tryptophan -Trp0X). For the next 28 days, half of the individuals continued to be fed with control pellets, whereas the other half was fed with Trp enriched ones (Trp8X). Body weight and length were assessed and blood samples taken at days 7 and 35. The following plasma steroids were examined by ELISA: cortisol, 11-ketotestosterone, testosterone and estradiol. At day 35, brains were dissected, separated in forebrain and hindbrain and homogenised. Brain monoamines, dopamine (DA) and 5-HT and their metabolites, DOPAC and 5-HIAA were measured by HPLC-EC. Results and Discussion We found two brain regions with immunoreactive cell bodies: the raphe and the ventral forebrain; in the latter, somata appeared in the NPPv, NRLd, NRLv and NRP. Abundant fibers were present throughout the whole brain, few of them entering the pituitary gland. Cd males, but not females, showed a greater forebrain serotonergic activity (5-HIAA/5-HT) (approx. 20%) when fed with Trp8X; although not significant, a tendency was observed towards higher forebrain 5-HIAA/5-HT (15%) in Af males fed with Trp8X. Dopaminergic activity (DOPAC/DA) did not vary within the experimental groups. The decrease in cortisol levels was higher in Cd males (about 30%), females (20%) and Af males (20%) fed with TRP8X. Body weight, length or sex hormones change did not differ between Trp0X vs. Trp8X fed animals. Conclusion TRP enriched diets increased brain serotonergic activity and reduced basal cortisol plasma concentrations but had no effect on growth or sexual steroid plasma levels.