title: Depressing Antidepressant: Fluoxetine Affects Serotonin Neurons Causing Adverse Reproductive Responses in Daphnia magna.
abstract: Selective serotonin reuptake inhibitors (SSRIs) are widely used antidepressants. As endocrine disruptive contaminants in the environment, SSRIs affect reproduction in aquatic organisms. In the water flea Daphnia magna, SSRIs increase offspring production in a food ration-dependent manner. At limiting food conditions, females exposed to SSRIs produce more but smaller offspring, which is a maladaptive life-history strategy. We asked whether increased serotonin levels in newly identified serotonin-neurons in the Daphnia brain mediate these effects. We provide strong evidence that exogenous SSRI fluoxetine selectively increases serotonin-immunoreactivity in identified brain neurons under limiting food conditions thereby leading to maladaptive offspring production. Fluoxetine increases serotonin-immunoreactivity at low food conditions to similar maximal levels as observed under high food conditions and concomitantly enhances offspring production. Sublethal amounts of the neurotoxin 5,7-dihydroxytryptamine known to specifically ablate serotonin-neurons markedly decrease serotonin-immunoreactivity and offspring production, strongly supporting the effect to be serotonin-specific by reversing the reproductive phenotype attained under fluoxetine. Thus, SSRIs impair serotonin-regulation of reproductive investment in a planktonic key organism causing inappropriately increased reproduction with potentially severe ecological impact.
authors.affiliation: Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA-CSIC) , Jordi Girona 18, E-08034, Barcelona, Spain.|Department of Zoology, Stockholm University , Svante Arrhenius väg 18A, S-106 91 Stockholm, Sweden.
authors.forename: Bruno
authors.initials: B
authors.lastname: Campos
authors.affiliation: Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA-CSIC) , Jordi Girona 18, E-08034, Barcelona, Spain.|Department of Zoology, Stockholm University , Svante Arrhenius väg 18A, S-106 91 Stockholm, Sweden.
authors.forename: Claudia
authors.initials: C
authors.lastname: Rivetti
authors.affiliation: Department of Zoology, Stockholm University , Svante Arrhenius väg 18A, S-106 91 Stockholm, Sweden.
authors.forename: Timm
authors.initials: T
authors.lastname: Kress
authors.affiliation: Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA-CSIC) , Jordi Girona 18, E-08034, Barcelona, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Barata
authors.affiliation: Department of Zoology, Stockholm University , Svante Arrhenius väg 18A, S-106 91 Stockholm, Sweden.
authors.forename: Heinrich
authors.initials: H
authors.lastname: Dircksen
mesh_terms: D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology; D003621:Daphnia / Q000187:drug effects*; D005473:Fluoxetine / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology
chemical_list: D000928:Antidepressive Agents; D005473:Fluoxetine; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors