Serotonergic outcome, stress and sexual steroid hormones, and growth in a South American cichlid fish fed with an L-tryptophan enriched diet

MORANDINI LEONEL; MARTIN RAMALLO; GUIMARAES MOREIRA R; SOMOZA GUSTAVO; SILVA ANA; PANDOLFI MATIAS

GENERAL AND COMPARATIVE ENDOCRINOLOGY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2015 vol. 223 p. 27 - 37

0016-6480

Reared animals for edible or ornamental purposes are frequently exposed to high aggression and stressfulsituations. These factors generally arise from conspecifics in densely breeding conditions. In vertebrates,serotonin (5-HT) has been postulated as a key neuromodulator and neurotransmitter involved in aggressionand stress. The essential amino acid L-tryptophan (trp) is crucial for the synthesis of 5-HT, and so,leaves a gateway for indirectly augmenting brain 5-HT levels by means of a trp-enriched diet. The cichlidfish Cichlasoma dimerus, locally known as chanchita, is an autochthonous, potentially ornamental speciesand a fruitful laboratory model which behavior and reproduction has been studied over the last 15 years.It presents complex social hierarchies, and great asymmetries between subordinate and dominant animalsin respect to aggression, stress, and reproductive chance. The first aim of this work was to performa morphological description of chanchita?s brain serotonergic system, in both males and females. Then, weevaluated the effects of a trp-supplemented diet, given during 4 weeks, on brain serotonergic activity,stress and sexual steroid hormones, and growth in isolated specimens. Results showed that chanchita?sbrain serotonergic system is composed of several populations of neurons located in three main areas:pretectum, hypothalamus and raphe, with no clear differences between males and females at a morphologicallevel. Animals fed with trp-enriched diets exhibited higher forebrain serotonergic activity and asignificant reduction in their relative cortisol levels, with no effects on sexual steroid plasma levels orgrowth parameters. Thus, this study points to food trp enrichment as a ??neurodietary?? method for elevatingbrain serotonergic activity and decreasing stress, without affecting growth or sex steroid hormonelevels.