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:Background: Examining transcriptional regulation by existing antidepressants in key neural circuits implicated in depression, and understanding the relationship to transcriptional mechanisms of susceptibility and natural resilience, may help in the search for new therapeutics. Further, given the heterogeneity of treatment response in human populations, examining both treatment response and non-response is critical. Methods: We compared the effects of a conventional monoamine-based tricyclic antidepressant, imipramine (14 daily injections), and a rapidly acting, experimental, non-monoamine-based antidepressant, ketamine (single injection), in mice subjected to chronic social defeat stress, a validated model of depression, and used RNA-sequencing to analyze transcriptional profiles associated with susceptibility, resilience and antidepressant response and non-response in prefrontal cortex (PFC), nucleus accumbens, hippocampus, and amygdala. Results: We identified approximately equal numbers of responder and non-responder mice following ketamine or imipramine treatment. Ketamine induced more expression changes in hippocampus than other brain regions; imipramine induced more expression changes in nucleus accumbens and amygdala. Transcriptional profiles in ketamine and imipramine responders were most similar in PFC, where the least transcriptional regulation occurred for each drug. Non-response reflected both the lack of response-associated gene expression changes and unique gene regulation. In responders, both drugs reversed susceptible associated transcriptional changes as well as induced resilient associated transcription in PFC, with effects varying by drug and brain region studied. Conclusions: We generated a uniquely large resource of gene expression data in four inter-connected limbic brain regions implicated in depression and its treatment with imipramine or ketamine. Our analyses highlight the PFC as a key site of common transcriptional regulation by both antidepressant drugs and in both reversing susceptibility and inducing resilience associated molecular adaptations. In addition, we found region-specific effects of each drug suggesting both common and unique effects of imipramine versus ketamine. mRNA profiles of susceptibility to chronic social defeat stress as well as treatment response were generated across 4 separate brain regions, with a sample size of 3-5 per group.

Project description:Background: Examining transcriptional regulation by existing antidepressants in key neural circuits implicated in depression, and understanding the relationship to transcriptional mechanisms of susceptibility and natural resilience, may help in the search for new therapeutics. Further, given the heterogeneity of treatment response in human populations, examining both treatment response and non-response is critical. Methods: We compared the effects of a conventional monoamine-based tricyclic antidepressant, imipramine (14 daily injections), and a rapidly acting, experimental, non-monoamine-based antidepressant, ketamine (single injection), in mice subjected to chronic social defeat stress, a validated model of depression, and used RNA-sequencing to analyze transcriptional profiles associated with susceptibility, resilience and antidepressant response and non-response in prefrontal cortex (PFC), nucleus accumbens, hippocampus, and amygdala. Results: We identified approximately equal numbers of responder and non-responder mice following ketamine or imipramine treatment. Ketamine induced more expression changes in hippocampus than other brain regions; imipramine induced more expression changes in nucleus accumbens and amygdala. Transcriptional profiles in ketamine and imipramine responders were most similar in PFC, where the least transcriptional regulation occurred for each drug. Non-response reflected both the lack of response-associated gene expression changes and unique gene regulation. In responders, both drugs reversed susceptible associated transcriptional changes as well as induced resilient associated transcription in PFC, with effects varying by drug and brain region studied. Conclusions: We generated a uniquely large resource of gene expression data in four inter-connected limbic brain regions implicated in depression and its treatment with imipramine or ketamine. Our analyses highlight the PFC as a key site of common transcriptional regulation by both antidepressant drugs and in both reversing susceptibility and inducing resilience associated molecular adaptations. In addition, we found region-specific effects of each drug suggesting both common and unique effects of imipramine versus ketamine.

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Molecular regulation in the hippocampal dentate gyrus in the onset and treatment of depression

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