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Perinatal paroxetine exposure in Selcetively-bred Low Responder rats

ABSTRACT: Selective serotonin reuptake inhibitor (SSRI) antidepressants are the mainstay treatment for the 10-20% of pregnant and postpartum women who suffer major depression, but the effects of SSRIs on their children’s developing brain and later emotional health are poorly understood. SSRI use during pregnancy can elicit antidepressant withdrawal in newborns and increase toddlers’ anxiety and social avoidance. In rodents, perinatal SSRI exposure increases adult depression- and anxiety-like behavior, although certain individuals are more vulnerable to these effects than others. Our study establishes a rodent model of individual differences in susceptibility to perinatal SSRI exposure, utilizing selectively-bred Low Responder (LR) and High Responder (HR) rats that were previously bred for high versus low behavioral response to novelty. Pregnant HR/LR females were chronically treated with the SSRI paroxetine (10 mg/kg/day p.o.) to examine its effects on offspring’s emotional behavior and gene expression in the developing brain. Paroxetine treatment had minimal effect on HR/LR dams’ pregnancy outcomes or maternal behavior. We found that LR offspring, naturally prone to an inhibited/anxious temperament, were susceptible to behavioral abnormalities associated with perinatal SSRI exposure (which exacerbated their Forced Swim Test immobility), while high risk-taking HR offspring were resistant. Microarray studies revealed robust perinatal SSRI-induced gene expression changes in the developing LR hippocampus and amygdala (postnatal days 7-21), including transcripts involved in neurogenesis, synaptic vesicle components, and energy metabolism. These results highlight the LR/HR model as a useful tool to explore the neurobiology of individual differences in susceptibility to perinatal SSRI exposure.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE111362 | GEO | 2018/03/03

REPOSITORIES: GEO

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Project description:Innate differences in human temperament strongly influence how individuals cope with stress and predispose for specific types of psychopathology. The present study examines the developing brain in an animal model of temperamental differences to understand how altered neurodevelopment may engender differences in emotional reactivity that are stable throughout the animal’s life. We utilize selectively-bred High Responder (bHR) and Low Responder (bLR) rats that exhibit dramatic emotional behavior differences, with bHRs exhibiting exaggerated novelty-exploration, aggression, impulsivity and drug self-administration, and bLRs showing marked behavioral inhibition, exaggerated anxiety- and depressive-like behavior. Using Affymetrix microarrays, we assessed bLR/bHR gene expression in the developing brain on postnatal days (P)7, 14, and 21, focusing on the hippocampus and nucleus accumbens, two regions related to emotionality and known to differ in adult bLR/bHR rats. We found dramatic bLR/bHR gene expression differences in the P7 and P14 hippocampus, with minimal differences in the nucleus accumbens. Some of the most profound differences involved genes critical for neurodevelopment and synaptogenesis. Stereological studies evaluated hippocampal structure in developing bHR/bLR pups, revealing enhanced hippocampal volume and cell proliferation in bLR animals. Finally, behavioral studies showed that the bHR/bLR behavioral phenotypes emerge very early in life, with exploratory differences apparent at P16 and anxiety differences present by P25. Together these data point to specific brain regions and critical periods when the bHR/bLR phenotypes begin to diverge, which may eventually allow us to test possible therapeutic interventions to normalize extreme phenotypes (e.g. the anxiety-prone nature of bLRs or drug addiction proclivity of bHRs). 2x2x3 factorial design with N=6 per group. Factors as follows: 1) Two selectively bred strains of rats (derived from an original Sprague Dawley population) termed High Responders (HR) and Low Responders (LR), 2) Two brain regions, Hippocampus (HPC) and Nucleus Accumbens (N.Acc), 3) Three developmental timepoints, specifically postnatal days 7 (P7), 14 (P14) and 21 (P21).

Project description:Major depressive disorder (MDD) is the psychiatric disorder with the highest prevalence in the world. Pharmacological antidepressant treatment (AD), such as selective serotonin reuptake inhibitors [SSRI, i.e. fluoxetine (Flx)] is the first line of treatment for MDD. Despite its efficacy, lack of AD response occurs in numerous patients characterizing Difficult-to-treat Depression. ElectroConvulsive Therapy (ECT) is a highly effective treatment inducing rapid improvement in depressive symptoms and high remission rates of ~50–63% in patients with pharmaco-resistant depression. Nevertheless, the need to develop reliable treatment response predictors to guide personalized AD strategies and supplement clinical observation is becoming a pressing clinical objective. Here, we propose to establish a proteomic peripheral biomarkers signature of ECT response in an anxio/depressive animal model of non-response to AD. Using an emotionality score based on the analysis complementary behavioral tests of anxiety/depression (Elevated Plus Maze, Novelty Suppressed Feeding, Splash Test), we showed that a 4-week corticosterone treatment (35 μg/ml, Cort model) in C57BL/6JRj male mice induced an anxiety/depressive-like behavior. A 28-days chronic fluoxetine treatment (Flx, 18 mg/kg/day) reduced corticosterone-induced increase in emotional behavior. A 50% decrease in emotionality score threshold before and after Flx, was used to separate Flx-responding mice (Flx-R, n=18), or Flx non-responder mice (Flx-NR, n=7). Then, Flx-NR mice received 7 sessions of electroconvulsive seizure (ECS, equivalent to ECT in humans) and blood was collected before and after ECS treatment. Chronic ECS normalized the elevated emotionality observed in Flx-NR mice. Then, proteins were extracted from peripheral blood mononuclear cells (PBMCs) and isolated for proteomic analysis using a high-resolution MS Orbitrap. The proteomic analysis revealed a signature of 33 peripheral proteins associated with response to ECS (7 down- and 26 upregulated). These proteins were previously associated with mental disorders and involved in regulating pathways which participate to the depressive disorder etiology. remark for sample name : ECTR=Flx-NR-ES, C=cort/Veh, CFNR= Flx-NR

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Perinatal paroxetine exposure in Selcetively-bred Low Responder rats

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