Abstract
Exposure to selective serotonin reuptake inhibitors (SSRIs) during development may elicit long-term neuroadaptive changes that could alter the basal regulation of stress-associated physiological and behavioral processes later in life. Currently, the effects of juvenile fluoxetine exposure in rodent models appear to be dependent on the developmental window targeted as well as the duration of drug exposure. The zebrafish (Danio rerio) model is rapidly becoming a useful tool in pharmacological research and can be used to help elucidate some of the long-term effects of fluoxetine exposure prior to sexual maturation on neuroendocrine and behavioral stress markers. In the current study, juvenile zebrafish were chronically exposed to fluoxetine hydrochloride (0 or 100 μg/L) for 14 days (31–44 days post-fertilization (dpf)), then were left untreated until young adulthood. Starting at 90 dpf, basal neuroendocrine stress and behavioral responses of zebrafish were assessed. Cortisol was extracted from the young adult zebrafish body (trunk) and quantified via enzyme-linked immunosorbent assay (ELISA). Anxiety-like behaviors were assessed in response to introduction to the novel tank test. It was expected that juvenile exposure to fluoxetine would (1) reduce basal cortisol levels and (2) elicit anxiolytic effects in the novel tank test in adulthood. However, fluoxetine exposure during the juvenile period was not associated with alterations in basal levels of cortisol nor were there any significant changes in anxiety-like behavior in the young adult zebrafish. Thus, in zebrafish, it does not appear that SSRI exposure during the juvenile period has a long-term adverse or maladaptive impact on the basal expression of cortisol and anxiety-like behavior in adulthood. Further studies are needed to determine if SSRI exposure during this developmental window influences neuroendocrine and behavioral responses to acute stress.
Highlights
Adolescence is a developmental time marked by tremendous amounts of brain growth and plasticity
Chronic juvenile fluoxetine treatment did not alter trunk cortisol responses Trunk cortisol levels of zebrafish chronically treated with fluoxetine prior to maturation did not differ from control fish (Fig. 1)
Juvenile zebrafish exposed to fluoxetine for 14 days did not display any alterations in basal cortisol levels or anxiety-like behavior in the novel tank test when assessed in young adulthood
Summary
Adolescence is a developmental time marked by tremendous amounts of brain growth and plasticity. In rodent models, chronic SSRI treatment prior to sexual maturation can elicit unique and/or long-lasting effects that can persist until adulthood, such as changes in the brain’s serotonin-producing neurons (Maciag et al, 2006) and alterations in behavior (Ansorge et al, 2004; Oh et al, 2009; Iñiguez, Warren & Bolaños-Guzmán, 2010; Iniguez et al, 2014). These unpredictable and unexpected changes in brain structure or function may potentially preclude the use of serotonergic antidepressants in adulthood, should depression be a chronic, lifelong condition
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