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Hippocampal neuronal dematuration as a common effect of antidepressant treatments

ABSTRACT: The dentate gyrus (DG) of the hippocampus is one of major targets for antidepressant treatments. Our recent research has revealed that selective serotonin reuptake inhibitor (SSRI) treatment causes a long-lasting change in the phenotypes of mature dentate granule neurons to immature state in adult mouse DG. However, it is unknown whether this M-bM-^@M-^\dematurationM-bM-^@M-^] of DG is a common effect of antidepressant treatments and what mechanisms underlie it. Using electroconvulsive stimulation (ECS), a model of highly effective and fast-acting antidepressant therapy, here we show that neural stimulation via ECS induces rapid and lasting dematuration of granule neurons in DG. A single or few times of stimulation transiently reduced mature marker expression and mature synaptic functions. Repetitive stimulation converted this transient dematuration into a stable form lasting more than 1 month. Dematured granule neurons showed higher excitability, and an increase in GABA-mediated inhibition by the benzodiazepine diazepam prevented the lasting maintenance phase of dematuration without affecting the initial induction phase. Our study suggests that dematuration of DG is a common cellular mechanism underlying effects of different types of antidepressant treatments, and demonstrate a novel role for excitation/inhibition balance in bidirectional regulation of the state of neuronal maturation in the adult brain. Mice were decapitated after the 11 times of ECS (or Sham) or 4 weeks treatment of fluoxetine (or vehicle) at a dose of 22 mg/kg. The brains were sliced and the frequency facilitation of mossy fiber synapse was measured in each sample. The samples which exhibited low frequency facilitation were selected to be used as dematured DG (n = 3) and the dentate gyrus was dissected from each sample. Total RNA was extracted by using an RNeasy micro kit (Qiagen) and the samples of the same groups were put together. From each group, 100 ng of total RNA was amplified with 3M-bM-^@M-^YIVT Express kit (Affymetrix, Inc., Santa Clara, CA, USA). All samples were hybridized to the GeneChip mouse genome 430A 2.0 array (Affymetrix, Inc.), and the microarray suite 5.0 of the Affymetrix gene chip operating software was used for the analysis of the GeneChip data.

ORGANISM(S): Mus musculus

SUBMITTER: Eri Segi-Nishida

PROVIDER: E-GEOD-54307 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Major depression is a multidimensional disorder highly prevalent in modern society. Although several classes of antidepressants (ADs) are currently available to treat depression, the effectiveness of treatment is still limited, as many patients do not show full remission; thus, there is a need to find better patients’ directed therapeutic strategies. Neuroplastic changes in several brain regions, namely in the hippocampal dentate gyrus (DG), are amongst the best correlates of depression and of ADs actions. In this study the targets and molecular mediators of chronic stress and of four ADs from different pharmacological classes (fluoxetine, imipramine, tianeptine and agomelatine) were investigated in the DG. Using the unpredictable chronic mild stress (uCMS) animal model of depression, the molecular commonalities and specificities of the ADs were determined. All ADs, except agomelatine, could reverse the behavioral deficits produced by uCMS, and the neuroplastic changes in the DG; agomelatine reversed only the anhedonic profile in the sucrose consumption test. Chronic stress induced mild but relevant molecular changes that were mostly reversed by fluoxetine, imipramine and tianeptine. Fluoxetine reduced pro-inflammatory response and increased cell metabolism pathways. Its actions were mostly dependent on molecular changes occurring in neurons. Similarities were found between imipramine and tianeptine molecular actions and targets, as both activated pathways related to cellular protection. Moreover, no particular neural cell type enrichment was found with both treatments. Agomelatine presented a very dissimilar molecular pattern impacting greatly on Rho-GTPases-related pathways in oligodendrocytes and neurons. The recognition of these molecular alterations contributes to the understanding of the processes implicated in the onset and treatment of depression and may pave the way for more effective therapeutic interventions. We compared gene expresssion in the dentate gyros of rats which were either untreated, exposed to unpredictable chronic mild stress, or exposed to the same stress and treated with either fluoxetine, imipramine, tianeptine, or agomelatine

Project description:Rationale Electroconvulsive seizure (ECS) therapy is a nonchemical treatment for depression. Since ECS up-regulates expression of c-Fos in the paraventricular nucleus of hypothalamus (PVN), the function of which is frequently influenced in depression, we hypothesized that ECS modulates functions of the PVN and contributes to its antidepressant effects. Objectives To identify gene expression changes in the mouse PVN by ECS treatment Material and methods First, we established a method to amplify nucleotides from small quantities of RNA. Mice received one shock of ECS and their brains were collected at 2 or 6 h after shock. The PVN was microdissected from dehydrated brain sections, its total RNA was extracted and microarray analysis was applied. Results At 2 h after ECS, 2.6% (589 genes) of the probes showed more than 2-fold decrease, and 0.9% (205 genes) showed more than 2-fold increase. To confirm the expression changes, genes showing differential expression with a wide range in the microarray were analyzed by qPCR. Among the genes with more than 2-fold change by ECS, down-regulated 94 genes and up-regulated 24 genes have been reported the association with anxiety, bipolar disorder or mood disorder by the Ingenuity knowledge database. The groups of down-regulated genes, which are suggested to modulate the function of the PVN or associate to psychiatric disorders, include neuropeptides (Cck), kinases (Prkcb, Prkcc, Camk2a), transcription factors (Bcl6, Tbr1), transporters (Aqp4) and others (Fmr1). Conclusion The present results indicate that ECS treatment can modulate the functions of PVN via a series of gene expression changes, and may contribute to its antidepressant effects at least in part. Mice received one shock of ECS and their brains were collected at 2 h (PVN_ECS2h_1, PVN_ECS2h_2) or 6 h after shock (PVN_ECS6h_1, PVN_ECS6h_2). The brains of sham-treated animals were collected at 2 h after treatment (PVN_sham_1, PVN_sham_2). The PVN was microdissected from dehydrated brain sections, and its total RNA was extracted. RNA samples from two or three animals were pooled to minimize the impact of biological variance. After nucleotide amplification by the ovation amplification, the gene expression profiles were obtained by the Affymetrix microarray analysis. The microarray analysis was performed twice using different sets of animals.

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Hippocampal neuronal dematuration as a common effect of antidepressant treatments

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