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

Abstract Under certain circumstances, some nutrients can affect the synthesis of central neurotransmitters and potentially behavior. The aim of this study was to characterize the influence of tryptophan supplementation on potential anxiety-like behaviors in zebrafish (Danio rerio), as well as to assess the suitability of a new standardized diet formulation for the better maintenance and performance of this species. To achieve this, the proportion of the amino acid tryptophan supplementation was experimentally modified at 5%, 50%, and 100% levels, individually, in the zebrafish diet. The investigation was conducted through the Y-maze test, light-dark preference test, and inhibitory avoidance test. The results indicated that tryptophan supplementation did not lead to the expected reduction in anxiety-like effects in the Y-maze and light-dark tests. However, a significant difference in avoidance times was observed in the inhibitory avoidance test between the groups with 5% and 50% supplemented diets, but a significant difference in avoidance times was observed in the inhibitory avoidance test between the groups with 5% and 50% supplemented diets. Changing the diet did not alter the animal's learning or natural anxiety. However, in most animals, tryptophan supplementation led to a decrease in body mass.