Origens do desenvolvimento do estado desamparado em zebrafish (Danio rerio): influência do estresse precoce e da exposição fetal ao álcool

Abstract

Several events that occur in the early years of ontogenetic development can cause disturbances that are observed later, such as behavioral and cognitive changes that appear in youth or even in adulthood. The developmental origins of health and disease (DOHAD) links the occurrence of early disorders, early in ontogeny, to the development of later physiological, behavioral, and psychological disorders. Several stressors present in the environment are considered risk factors, these stressors are conceptualized as circumstances that threaten physical integrity or psychological well-being, and can bring various harm to health. In this sense, the present work aimed to examine the influence of unpredictable emotional stress (ECI) and alcohol exposure in the early stages of development (embryonic and larval stages) on the helpless behavior of zebrafish. In the state of helplessness, individuals have difficulties in the alert response and in the ability to avoid adverse situations as a result of exposure to uncontrollable aversive stimuli. Thus, in the first chapter, we propose a new tool to assess the state of helplessness in zebrafish, the hypoxia escape test. We observed that the proposed test is efficient in stimulating the escape motivation, which is preserved in controlled animals and in animals treated with anxiolytics. However, escape was significantly reduced in animals previously exposed to ECI and alcohol, as well as in animals treated with a monoamine reuptake blocking agent (reserpine). In the second chapter, we used the same stressors (ECI and alcohol) and tested helpless-like behavior through the tail grasp test and active shock avoidance (protocols already validated). We observed that stressors were able to influence the development of depression and helplessness in both testicles. Finally, our results indicate that exposure to aversive events early in life (represented by ECI and fetal alcohol exposure) may contribute to the development of the helpless state. In addition, our study shows that the zebrafish is a suitable animal model for tests that address states of depression and helplessness, and highlights the importance of the model as a tool in the search for therapies and treatments that can alleviate or prevent the development of this condition.