Tryptophan supplementation reduces body weight but does not decrease anxiety-like behavior in zebrafish

Under certain circumstances, some nutrients can affect the synthesis of central neurotransmitters and potentially influence behavior. The objective of this study was to characterize the influence of tryptophan supplementation on anxiety-like behavior in zebrafish (Danio rerio) and to assess the suitability of a new formulation of standardized diet for enhancing the maintenance and performance of this species. To achieve this, the proportion of the amino acid tryptophan was experimentally modified through supplementation at 5%, 50%, and 100% of its original levels in the zebrafish diet. The investigation was conducted using the Y-maze test, light-dark preference test and inhibitory avoidance test. The results indicated that tryptophan supplementation did not lead to a reduction in anxiety-like behavior in any of the tests conducted, suggesting a direct relationship between the individual isolation of these animals and the predominance of this type of behavior. Furthermore, a significant difference was observed in the inhibitory avoidance test between groups with diets supplemented at 5% and 50%. The dietary modification did not alter the learning of natural anxiety, but in most animals, tryptophan supplementation led to a decrease in body mass.