The role of an oxytocin-like peptide in social reward in zebrafish

• Main Author: Santos, Daniela Filipa Travanca dos
• Publication Date: 2017
• Format: Master thesis
• Language: eng
• Source: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Download full: http://hdl.handle.net/10773/22008
• topic: Peixe - zebra; Comportamento animal; Péptidos

Zebrafish (Danio rerio) live in shoals and express a preference to associate with conspecifics from very early on during their development. This social motivation plays an important role for their survival, providing protection against predators and improving foraging and mating efficiency. Thus, it has been hypothesized that conspecifics have acquired a reward property (as known as social reward) in social living animals, that promotes group living. The aim of this project is to investigate the occurrence of social reward in zebrafish and to characterize its neural mechanisms. Given the role of oxytocin in the regulation of social behaviour across vertebrates we hypothesized that isotocin (the fish homologue of oxytocin) can be involved in social reward in zebrafish. We have used, for the first time, a social conditioned place preference (CPP) paradigm in this species, in order to assess the rewarding value of conspecifics versus an established non-social reward in zebrafish (e.g. food). Subsequently, we used a knockout (KO) line for the oxytocin receptor to assess the impact of oxytocin on social reward. We were able to demonstrate that adult male zebrafish perform CPP towards a social reward of conspecifics. Yet, this experiment showed that social stimulation has the same reward property as non-social stimulation for adult male zebrafish, and that oxytocin-like peptides seems to be involved in the social reward system. Finally, we have used the expression of a phosphorylation protein (pS6) as a marker of neuronal activity to map the brain regions involved in social reward in zebrafish, as well as the expression of tyrosine hydroxylase (TH) as a marker of the dopaminergic system. Further immunohistochemical assays need to be performed in order to uncover the role of oxytocin in the regulation of the social reward system. However, our preliminary results highlight the significance of social stimulation, in zebrafish, by revealing relevant differences in brain activation in the ventral telencephalic area, more specifically in the dorsal nucleus and in the supracommisural nucleus.