Ontogenia do comportamento tipo-ansioso em larvas de zebrafish (Danio rerio): avaliação preliminar do paradigma comportamental do labirinto em cruz com rampa (LCR)

Abstract

From the simplest to the most complex organisms, the ability to avoid aversive stimuli is essential for survival. Approach toward desirable situations and avoidance of threatening ones are fundamental tasks, observable in both behavioral responses and biochemical alterations. Avoidance behavior may be linked to imminent danger or anticipation of future events based on specific cues. However, these responses are not always associated with natural homeostasis and may reflect pathological processes. Anxiety disorders represent a global public health challenge, affecting approximately one-third of the world’s population—with Brazil showing the highest prevalence. While genetic and hereditary factors contribute to these disorders, environmental variables play a predominant role, underscoring the need to understand their neurobiological origins and physiological responses. This study investigated the ontogeny of anxiety-like behavior in zebrafish larvae using the Ramped Cross Maze (RCM). We standardized parameters such as water height (1.3 cm for 5 dpf; 1.5 cm for 14/21 dpf) and test duration (6 min), demonstrating that older larvae exhibit increased avoidance of elevated areas, suggesting progressive maturation of neural circuits related to anxiety. Adapted from the rodent elevated plus maze, the ECM creates a conflict based on water column depth, analogous to classical anxiety paradigms. Larvae were tested in the RCM and light/dark test (LD) at different water heights (1.1 cm, 1.3 cm, and 1.5 cm) and developmental stages (5, 14, and 21 days post-fertilization). Results revealed that water height significantly influenced exploratory behavior, with 1.3 cm being optimal for 5 dpf larvae, and 1.5 cm for 14 and 21 dpf larvae. These findings indicate that zebrafish larvae display qualitatively distinct anxiety-like behaviors across developmental stages, and the RCM is a sensitive tool to detect such behaviors, advancing behavioral neuroscience. Beyond investigating the ontogeny of anxiety-like responses, full validation of the RCM could enable its application in pharmacological screenings and genetic studies aimed at understanding anxiety disorders. This study was approved by the Ethics Committee (CEUA, protocol 192/2023) and supported by Capes, CNPq, and Fapemig.