Behavioral and neurogenomic transcriptome changes in wild-derived zebrafish with fluoxetine treatment

Abstract

BackgroundStress and anxiety-related behaviors are seen in many organisms. Studies have shown that in humans and other animals, treatment with selective serotonin reuptake inhibitors (e.g. fluoxetine) can reduce anxiety and anxiety-related behaviors. The efficacies and side effects, however, can vary between individuals. Fluoxetine can modulate anxiety in a stereospecific manner or with equal efficacy regardless of stereoisomer depending on the mechanism of action (e.g. serotonergic or GABAergic effects). Zebrafish are an emerging and valuable translational model for understanding human health related issues such as anxiety. In this study we present data showing the behavioral and whole brain transcriptome changes with fluoxetine treatment in wild-derived zebrafish and suggest additional molecular mechanisms of this widely-prescribed drug.ResultsWe used automated behavioral analyses to assess the effects of racemic and stereoisomeric fluoxetine on male wild-derived zebrafish. Both racemic and the individual isomers of fluoxetine reduced anxiety-related behaviors relative to controls and we did not observe stereospecific fluoxetine effects. Using RNA-sequencing of the whole brain, we identified 411 genes showing differential expression with racemic fluoxetine treatment. Several neuropeptides (neuropeptide Y, isotocin, urocortin 3, prolactin) showed consistent expression patterns with the alleviation of stress and anxiety when anxiety-related behavior was reduced with fluoxetine treatment. With gene ontology and KEGG pathway analyses, we identified lipid and amino acid metabolic processes, and steroid biosynthesis among other terms to be over-enriched.ConclusionOur results demonstrate that fluoxetine reduces anxiety-related behaviors in wild-derived zebrafish and alters their neurogenomic state. We identify two biological processes, lipid and amino acid metabolic synthesis that characterize differences in the fluoxetine treated fish. Fluoxetine may be acting on several different molecular pathways to reduce anxiety-related behaviors in wild-derived zebrafish. This study provides data that could help identify common molecular mechanisms of fluoxetine action across animal taxa.

Can the behaviour of threespine stickleback parasitized with Schistocephalus solidus be replicated by manipulating host physiology?

“…Fluoxetine, for instance, causes in vitro contraction of gastric muscle through a cholinergic pathway (James et al, 2005) and slows gut movement in rats subjected to a force-swimming test (Xie et al, 2013). Behavioural effects of SSRI exposure have been shown in different fish species, although none of these previous studies have ruled out non-specific effects by using a separate treatment that combines exposure to a SSRI and to a serotonin antagonist to determine if it reverses the observed behavioural effects of SSRI completely (Gaworecki and Klaine, 2008;Wong et al, 2013;Hedgespeth et al, 2014;Sebire et al, 2015). Our results are thus consistent in methodology and findings with previous studies but do not rule out non-specific effects.…”

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“…In fathead minnows, Pimephales promelas, selective serotonin re-uptake inhibitors (SSRIs) result in increased latency to the initiation of escape response (Painter et al, 2009) and decrease predator avoidance (Weinberger and Klaper, 2014). In zebrafish, the SSRI fluoxetine increases the time spent in the top half of the tank (Wong et al, 2013). We thus administrated fluoxetine to manipulate the serotonin physiological regulatory network.…”

Developing ‘integrative’ zebrafish models of behavioral and metabolic disorders

“…In particular, several genes involved in blood coagulation, platelet activation, fatty acid, cholesterol and TG metabolism were dysregulated in both zebrafish and mammalian models of obesity [150], suggesting that the diet-induced obesity zebrafish models can help identify putative pharmacological targets for the treatment of human obesity. Interestingly, chronic treatment of zebrafish with antidepressant fluoxetine, in addition to causing strong anxiolytic action, has altered the expression of several genes, up-regulating genes of isotocin (a fish homolog of oxytocin) and NPY [239]. Fluoxetine treatment down-regulated zebrafish gamma aminobutyric acid (GABA) transporter, urocortin 3 (part of the CRH family, known to evoke anxiety in mammals) and prolactin (a stress-related hormone in mammals and zebrafish) [239].…”

“…Interestingly, chronic treatment of zebrafish with antidepressant fluoxetine, in addition to causing strong anxiolytic action, has altered the expression of several genes, up-regulating genes of isotocin (a fish homolog of oxytocin) and NPY [239]. Fluoxetine treatment down-regulated zebrafish gamma aminobutyric acid (GABA) transporter, urocortin 3 (part of the CRH family, known to evoke anxiety in mammals) and prolactin (a stress-related hormone in mammals and zebrafish) [239]. The genes related to lipid and small molecule metabolism were also over-enriched among those influenced by fluoxetine treatment [234], illustrating how metabolic and anxiety-related molecular pathways may overlap in zebrafish transcriptomic assays.…”