RESUMO
Zebrafish has been increasingly used in behavioral studies, but data can present high variability. Most studies have been performed using isolated zebrafish, despite their interactive nature and shoaling behavior. We compared adult zebrafish behavior and cortisol levels after exposure to novelty as well as sensitivity to Pentylenetetrazole (PTZ)-induced seizures in animals tested individually or in groups of three (triplets). In the exploratory behavior task, data from single fish and triplets were not significantly different, but single fish data were more disperse in latency, to enter and time spent in the tank upper part, and crossings. In the light-dark task, time in the light zone and crossings were not different between groups, but latency to enter the dark zone and data variability were. We also observed that the latency to reach stage III seizures induced by PTZ was higher in triplets, but data dispersion was not different from single fish. Finally, cortisol levels of fish individually exposed to a novel environment were higher and more variable than triplets, while both groups had higher levels than unmanipulated animals. Thus, when tested individually, zebrafish are more stressed and present more variable behavior due to disruption of their natural shoal strategies. These features can be beneficial or detrimental depending on study aims and should be considered when designing, analyzing, and interpreting zebrafish behavioral data.
Assuntos
Comportamento Social , Estresse Psicológico , Peixe-Zebra , Animais , Ansiedade , Hidrocortisona/sangue , Masculino , Pentilenotetrazol , Peixe-Zebra/sangueRESUMO
Zebrafish (Danio rerio) have emerged as a promising model organism to study development, toxicology, pharmacology, and neuroscience, among other areas. Despite the increasing number of studies using zebrafish, behavioral studies with this species are still elementary when compared to rodents. The aim of this study was to develop a model of unpredictable chronic stress (UCS) in zebrafish. We evaluated the effects of UCS protocol during 7 or 14 days on behavioral and physiological parameters. The effects of stress were evaluated in relation to anxiety and exploratory behavior, memory, expression of corticotrophin-releasing factor (CRF) and glucocorticoid receptor (GR), and cortisol levels. As expected, UCS protocol increased the anxiety levels, impaired cognitive function, and increased CRF while decreased GR expression. Moreover, zebrafish submitted to 7 or 14 days of UCS protocol presented increased cortisol levels. The protocol developed here is a complementary model for studying the neurobiology and the effects of chronic stress in behavioral and physiological parameters. In addition, this protocol is less time consuming than standard rodent models commonly used to study chronic stress. These results confirm UCS in zebrafish as an adequate model to preclinical studies of stress, although further studies are warranted to determine its predictive validity.