Relação entre o sistema imune e o comportamento em zebrafish

Abstract

The interaction between immune system and behavior has already been observed in several studies using mammals as animal model. On the other hand, this relationship has not yet been clearly demonstrated in other animal species including fish. Thus, the main objective of this work is to evaluate the relationship between immune system and zebrafish behavior. To achieve our goals, we already carried out three fundamental studies that will be central to this Doctoral Thesis. In the first study, we separated fish according to their social and exploratory behavior and evaluated the expression of cytokines genes in the brain. So we verify that the immunological status varies according to the exploratory and social profile of the fish. Although we showed that there is a relationship between immune system and zebrafish behavior, a major question remains open: is the immune system that leads to behavioral pattern changes or is it the behavioral pattern that alters the immune response? To answer this question, in our second study, we induced an inflammatory response in a group of fish and reevaluated the exploratory and social behavior as well as the expression of cytokine genes in the brain. Sick fish had increased expression of proinflammatory cytokines in the brain and decreased locomotion, social preference and exploration to a new object when compared to the control group. With this study we demonstrated that the immune system changes the behavior, and we first characterized the sickness behavior in the zebrafish. Finally, in the third study we evaluated the effects of acute and chronic stress on the expression of cytokines and neuronal markers in the zebrafish brain, noting that chronic stress causes significant changes in these genes, whereas a single episode of stress did not cause changes. Thus we demonstrate that a behavioral pattern, such as stress, causes changes in the immune response. Therefore, we conclude that immune system and behavior are interconnected, and one can alter the other.