Modulação opioide nas interações agonísticas do peixe-donzela (Stegastes fuscus)

Abstract

Endogenous opioids are neurotransmitters that play a crucial role in pain and stress regulation. They have also been identified as key modulators of the reward system across various species. In this context, the present study investigated the role of the opioid system in associative conditioning based on social reinforcement in the damselfish (Stegastes fuscus). The fish were collected, acclimated to laboratory conditions, and subjected to a conditioned place preference (CPP) test, where the reinforcement used was the presence of a conspecific that elicits aggressive behavior—a widely observed innate trait in this species. We employed an opioid agonist (DAMGO) and an antagonist (Naloxone) to modulate the reward system and analyze the resulting behavioral changes. DAMGO administration did not affect conditioning compared to the control group. Similarly, opioid blockade with Naloxone did not alter the pursuit of the reward. These findings suggest that the drive for interaction with conspecifics is not mediated by the opioid system, although alterations in this neurotransmission pathway may modulate behavioral expression. Thus, the place preference expressed under the influence of Naloxone and DAMGO needs to be further evaluated by incorporating the animals' agonistic responses. Additionally, future studies should explore the involvement of dopaminergic drugs to better understand the dissociation between motivation and reward-seeking behavior in fish. Further research into the expression and neurobiological basis of aggressive behavior in this species is also necessary to validate its rewarding nature and its relationship with well-being.