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

LEONEL MORANDINI; MARTÍN RAMALLO; RENATA GUIMARAES MOREIRA; CHRISTIAN HÖCHT; GUSTAVO M. SOMOZA; ANA SILVA; MATÍAS PANDOLFI

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 stressful situations. 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 aggression and stress. The essential amino acid L-tryptophan (TPH) is crucial for the synthesis of 5-HT, and so, leaves a gateway for indirectly augmenting brain 5-HT levels by means of a TPH-enriched diet. The cichlid fish Cichlasoma dimerus, locally known as chanchita, as any other cichlid, presents complex social hierarchies, and great asymmetries between subordinate and dominant animals in respect to aggression, stress, and reproductive chance. These fish have ornamental interest so a simple way to reduce stress may be important from the point of view of production. In this context, the first aim of this work was to perform a morphological description of chanchita?s brain serotonergic system, in both males and females. Then, we evaluated the effects of a TPH-supplemented diet, given during 4 weeks, on brain serotonergic activity, stress and sexual steroid hormones, and growth in isolated specimens. Results showed that chanchita?s brain 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 morphological level. Animals fed with TPH-enriched diets exhibited higher forebrain serotonergic activity and a significant reduction in their relative cortisol levels, with no effects on sexual steroid plasma levels or growth parameters. This study thus points to consider food TPH enrichment as a ??neurodietary?? method for elevating brain serotonergic activity and decreasing stress, without affecting growth or sex steroid hormone levels.