Stress-Induced Changes of Hippocampal NMDA Receptors: Modulation by Duloxetine Treatment

It is now well established that the glutamatergic system contributes to the pathophysiology of depression. Exposure to stress, a major precipitating factor for depression, enhances glutamate release that can contribute to structural abnormalities observed in the brain of depressed subjects. On the other hand, it has been demonstrated that NMDA antagonists, like ketamine, exert an antidepressant effect at preclinical and clinical levels. On these bases, the purpose of our study was to investigate whether chronic mild stress is associated with specific alterations of the NMDA receptor complex, in adult rats, and to establish whether concomitant antidepressant treatment could normalize such deficits. We found that chronic stress increases the expression of the obligatory GluN1 subunit, as well as of the accessory subunits GluN2A and GluN2B at transcriptional and translational levels, particularly in the ventral hippocampus. Concomitant treatment with the antidepressant duloxetine was able to normalize the increase of glutamatergic receptor subunit expression, and correct the changes in receptor phosphorylation produced by stress exposure. Our data suggest that prolonged stress, a condition that has etiologic relevance for depression, may enhance glutamate activity through post-synaptic mechanisms, by regulating NMDA receptors, and that antidepressants may in part normalize such changes. Our results provide support to the notion that antidepressants may exert their activity in the long-term also via modulation of the glutamatergic synapse

Notulae to the Italian alien vascular flora: 12

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1

Modulation of protein levels for NMDA receptor subunits by CMS and antidepressant treatment in rat ventral hippocampus.

<p>The protein levels of GluN1 (A), GluN2A (B) and GuN2B (C) were measured in the crude synaptosomal fraction of ventral hippocampus of non stressed and chronically stressed rats, treated for 21 days with vehicle or duloxetine and killed 24 hours after the last stress. The data, expressed as a percentage of No Stress/Vehicle (set at 100%), are the mean ± SEM of at least 5–7 independent determinations. *p<0.05 vs. No Stress/Vehicle; ^$p<0.05, ^$$p<0.01 vs. Stress/Vehicle (two-way ANOVA with SCPHT).</p

Conditions of the antibodies used in the Western blot analysis.

<p>Conditions of the antibodies used in the Western blot analysis.</p

Representative Western blotting of NMDA receptor subunits in ventral hippocampus.

<p>Representative western blot analysis of of GluN1, GluN2A, GluN2B, phospho GluN1 (Ser896), phospho GluN1 (ser897), phospho GluN2B (Ser1303), phospho GluN2B (Tyr1472) expression in crude synaptosomal fraction from adult brain ventral hippocampus. β-actin is shown as control for comparison. Veh vehicle, dlx duloxetine, CMS chronic mild stress, CMS + dlx chronic mild stress + duloxetine. Experimental conditions are described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037916#s2" target="_blank">Material and Methods</a>.</p

Sequences of forward and reverse primers used in real time PCR analysis.

<p>Sequences of forward and reverse primers used in real time PCR analysis.</p

Modulation of GluN1 and GluN2B subunits phosphorylation by CMS and antidepressant treatment in rats ventral hippocampus.

<p>The levels of pGluN1Ser896 and pGluN1Ser897 (A,B) or pGluN2BSer1303 and pGluN2BTyr1472 (C,D) were measured in the crude synaptosomal fraction of ventral hippocampus of non stressed and chronically stressed rats, treated for 21 days with vehicle or duloxetine and killed 24 hours after the last stress. The data represent the ration between phosphorylated and total subunit levels. Results, expressed as a percentage of No Stress/Vehicle (set at 100%), are the mean ± SEM of at least 5–7 independent determinations. *p<0.05, **p<0.01 vs. No Stress/Vehicle; ^$p<0.05 vs. Stress/Vehicle (two-way ANOVA with SCPHT).</p

Modulation of NMDA receptor subunits expression by chronic stress and antidepressant treatment <i>in rat brain.</i>

<p>The mRNA levels of GluN1 <i>(</i><b><i>A, D, G</i></b><i>),</i> GluN2A <i>(</i><b><i>B, E, H</i></b><i>)</i> and GuN2B <i>(</i><b><i>C, F, I</i></b><i>)</i> were measured in ventral hippocampus <i>(</i><b><i>A, B, C</i></b><i>), </i><b><i>dorsal hippocampus</i></b><i> (</i><b><i>D, E, F</i></b><i>) </i><b><i>and prefrontal cortex</i></b><i> (</i><b><i>G, H, I</i></b><i>)</i> of non stressed and chronically stressed rats, treated for 21 days with vehicle or duloxetine and killed 24 hours after the last stress. The data, expressed as a percentage of No Stress/Vehicle (set at 100%), are the mean ± SEM of at least 10–12 independent determinations. *p<0.05, **p<0.01, ***p<0.01 vs. No Stress/Vehicle; <i>^$</i><b><i>p<0.05</i></b>, ^$$$p<0.001 vs. Stress/Vehicle (two-way ANOVA with SCPHT).</p

Lack of serotonin transporter alters BDNF expression in the rat brain during early postnatal development

Item does not contain fulltextIt is well established that alterations of the serotoninergic system may contribute to the pathophysiology of mood disorders. Accordingly, it has been demonstrated that genetic deletion of the serotonin transporter (SERT) in rodents leads to an anxious and depressive phenotype, which is also associated with reduced neuronal plasticity. Indeed, we have demonstrated that adult SERT(-/-) animals show decreased brain-derived neurotrophic factor (BDNF) expression, as well as reduced levels of transcription factor regulating the neurotrophin transcription. While these changes may represent long-term consequences of impaired function of the transporter during development, no information exists with respect to the developmental profile of such changes. Using SERT(-/-) rats at different ages, we found that the impairment in neuroplasticity originates early in development and worsens during the first 3 weeks of life. Indeed, we observed that BDNF expression was reduced at birth and that the magnitude of these changes became more pronounced starting from PND21, being sustained by epigenetic mechanisms as well as alterations in the expression of specific transcription factors, including Npas4 and CaRF. These results suggest that an impairment of SERT may affect BDNF expression throughout postnatal development. These early changes may increase stress susceptibility during critical windows of brain maturation, which may eventually lead to the heightened predisposition to mood disorders found in individual carrying genetic variants of the serotonin transporter