CUS-induced Depressive-like Behavior Research Articles

Exercise alleviates CUS-induced depressive-like behaviors by modulating paracellular and transcellular permeability of the blood-brain barrier in the prefrontal cortex

BackgroundIncreased blood-brain barrier (BBB) permeability is implicated in the pathophysiology of major depressive disorder (MDD). While aerobic exercise has shown promise in mitigating MDD symptoms by potentially preserving BBB integrity, the detailed mechanisms remain unclear. This study explores these mechanisms to assess aerobic exercise's therapeutic potential for MDD. MethodsMale C57BL/6 J mice were used in this study to investigate the effects of aerobic exercise on CUS-induced BBB permeability and depressive-like behaviors. Chronic unpredictable stress (CUS)-induced MDD mouse models were divided into three groups: Control, CUS, and CUS+Exercise. We monitored body weight, blood S100β levels, and cytokines via ELISA. Claudin-5 and Caveolin-1 (CAV-1) expressions in the medial prefrontal cortex were evaluated using Western blotting and immunofluorescence. BBB permeability was assessed using biocytin-TMR and Alb-Alexa 594 tracers. Transmission electron microscopy was used to observe ultrastructural changes in the BBB directly. Depression-related behaviors were tested through several behavioral assays. ResultsCUS significantly increased CAV-1 expression and Alb-Alexa 594 leakage, suggesting enhanced transcellular BBB permeability. Despite unchanged Claudin-5 levels, its tight junction ultrastructure was altered, leading to increased biocytin-TMR leakage. Aerobic exercise ameliorated these disruptions, reduced inflammatory cytokines, and improved behavioral outcomes in CUS mice. ConclusionDisruptions in both paracellular and transcellular BBB pathways are pivotal in depression development. Aerobic exercise offers potential therapeutic benefits for MDD linked with BBB dysfunction by mitigating stress-induced structural and functional changes.

Roles of miR-432 and circ_0000418 in mediating the anti-depressant action of ADAR1

Adenosine deaminase acting on RNA1 (ADAR1) is a newly discovered epigenetic molecule marker that is sensitive to environmental stressors. A recent study has demonstrated that ADAR1 affects BDNF expression via miR-432 and is involved in antidepressant action. However, the detailed molecular mechanism is still unclear. We have uncovered a new molecular mechanism showing the involvement of miR-432 and circ_0000418 in mediating the antidepressant action of ADAR1. We demonstrate that the ADAR1 inducer (IFN-γ) alleviates the depressive-like behaviors of BALB/c mice treated with chronic unpredictable stress (CUS) exposure. Moreover, both in vivo and in vitro studies show that ADAR1 differently impacts miR-432 and circ_0000418 expressions. Furthermore, the in vitro results demonstrate that circ_0000418 oppositely affects BDNF expression. Together, our results indicate that ADAR1 affects CUS-induced depressive-like behavior and BDNF expression by acting on miR-432 and circ_0000418. Elucidation of this new molecular mechanism will not only provide insights into further understanding the important role of ADAR1 in stress-induced depressive-like behavior but also suggest a potential therapeutic strategy for developing novel anti-depressive drugs.

MiR-497 promotes microglia activation and proinflammatory cytokines production in chronic unpredictable stress-induced depression via targeting FGF2

Depression is one of important prevalent psychiatric disorders worldwide. MiR-497 is considered as a diagnostic biomarker and a promising therapeutic target in cancers. However, the role of miR-497 in depression remains unknown. In this study, we demonstrated that CUS induced depression-like behaviors and overexpression of miR-497 in rats. Interestingly, knockdown miR-497 ameliorated CUS-induced depressive-like behavior in rats. Moreover, knockdown of miR-497 inhibited the activation of microglia and the production of proinflammatory cytokines including IL-6, IL-1β, MCP-1 and TNF-α in CUS-induced rats. Luciferase activity assay proved that Fibroblast Growth Factor-2 (FGF2) was a direct target of miR-497 and modulated by miR-497 in microglia. In rescue experiments, overexpression of FGF2 inhibited miR-497-induced proinflammatory cytokines and iNOS expression. These results showed that miR-497 aggravated hippocampal microglial activation in CUS-induced depression in rat via targeting FGF2, providing a novel potential target for treatment of depression.

Antidepressive properties of macrophage-colony stimulating factor in a mouse model of depression induced by chronic unpredictable stress

Previous studies have reported that macrophage-colony stimulating factor (M-CSF), a drug that is used to treat hematological system disease, can ameliorate chronic stress-induced depressive-like behaviors in mice. This indicates that M-CSF could be developed into a novel antidepressant. Here, we investigated the antidepressive properties of M-CSF, aiming to explore its potential values in depression treatment. Our results showed that a single M-CSF injection at the dose of 75 and 100 μg/kg, but not at 25 or 50 μg/kg, ameliorated chronic unpredictable stress (CUS)-induced depressive-like behaviors in mice at 5 h after the drug treatment. In a time-dependent experiment, a single M-CSF injection (100 μg/kg) was found to ameliorate the CUS-induced depressive-like behaviors in mice at 5 and 8 h, but not at 3 h, after the drug treatment. The antidepressant effect of the single M-CSF injection (100 μg/kg) in chronically-stressed mice persisted at least 10 days and disappeared at 14 days after the drug treatment. Moreover, 14 days after the first injection, a second M-CSF injection (100 μg/kg) still produced antidepressant effects at 5 h after the drug treatment in chronically-stressed mice who re-displayed depressive-like phenotypes. The antidepressant effect of M-CSF appeared to be mediated by the activation of the hippocampal microglia, as pre-inhibition of microglia by minocycline (40 mg/kg) or PLX3397 (290 mg/kg) pretreatment prevented the antidepressant effect of M-CSF in CUS mice. These results demonstrate that M-CSF produces rapid and sustained antidepressant effects via the activation of the microglia in the hippocampus in a dose- and time-dependent manner.

Ketamine rapidly reverses stress-induced impairments in GABAergic transmission in the prefrontal cortex in male rodents

Dysfunction of medial prefrontal cortex (mPFC) in association with imbalance of inhibitory and excitatory neurotransmission has been implicated in depression. However, the precise cellular mechanisms underlying this imbalance, particularly for GABAergic transmission in the mPFC, and the link with the rapid acting antidepressant ketamine remains poorly understood. Here we determined the influence of chronic unpredictable stress (CUS), an ethologically validated model of depression, on synaptic markers of GABA neurotransmission, and the influence of a single dose of ketamine on CUS-induced synaptic deficits in mPFC of male rodents. The results demonstrate that CUS decreases GABAergic proteins and the frequency of inhibitory post synaptic currents (IPSCs) of layer V mPFC pyramidal neurons, concomitant with depression-like behaviors. In contrast, a single dose of ketamine can reverse CUS-induced deficits of GABA markers, in conjunction with reversal of CUS-induced depressive-like behaviors. These findings provide further evidence of impairments of GABAergic synapses as key determinants of depressive behavior and highlight ketamine-induced synaptic responses that restore GABA inhibitory, as well as glutamate neurotransmission.

Gut microbiota from NLRP3-deficient mice ameliorates depressive-like behaviors by regulating astrocyte dysfunction via circHIPK2

BackgroundInflammasomes have been found to interact with the gut microbiota, and this effect is associated with depression, but the mechanisms underlying this interaction have not been elucidated in detail.ResultsThe locomotor activity of NLRP3 KO mice was significantly greater than that of their WT littermates, while cohousing and transplantation of the NLRP3 KO gut microbiota avoid the effects of NLRP3 KO on the general locomotor activity at baseline. Meanwhile, transplantation of the NLRP3 KO microbiota alleviated the CUS-induced depressive-like behaviors. The compositions of the gut microbiota in NLRP3 KO mice and WT mice were significantly different in terms of the relative abundance of Firmicutes, Proteobacteria, and Bacteroidetes. Fecal microbiota transplantation (FMT) from NLRP3 KO mice significantly ameliorated the depressive-like behavior induced by chronic unpredictable stress (CUS) in recipient mice. Given the correlation between circular RNA HIPK2 (circHIPK2) and depression and the observation that the level of circHIPK2 expression was significantly increased in CUS-treated mice compared with that in the control group, further experiments were performed. FMT significantly ameliorated astrocyte dysfunction in recipient mice treated with CUS via inhibition of circHIPK2 expression.ConclusionsOur study illustrates the involvement of the gut microbiota-circHIPK2-astrocyte axis in depression, providing translational evidence that transplantation of the gut microbiota from NLRP3 KO mice may serve as a novel therapeutic strategy for depression.

Antidepressant-like effects of embelin and its possible mechanisms of action in chronic unpredictable stress-induced mice

Objectives Embelin, a principal active constituent of embelin ribes burm, has good therapeutic effects on various diseases. To explore the effects and underlying mechanisms of embelin on depression, we made a preliminary study to clarify this issue.Methods We first used chronic unpredictable stress (CUS) to construct the model of depression in mice. Then, we determined the effects of embelin on CUS-induced behavioral dysfunction using open field test, sucrose preference test, tail suspension test and forced swimming test. Furthermore, we used the biological experiments to evaluate the changes of brain-derived neurotrophic factor (BDNF), oxidative stress, neuronal inflammation and the hypothalamic pituitary adrenal (HPA) axis after embelin treatment.Results The behavioral tests indicated embelin indeed had efficient antidepressant effects. Moreover, enhanced BDNF expression, decreased oxidative stress markers (TBARS, nitric oxide) activities, elevated antioxidants (total thiol, catalase) expression, decreased pro-inflammatory cytokines (IL-6, TNF-α, IL-1β and COX-2) expression and normalized the HPA axis activity were found after embelin treatment in CUS-induced mice. Hence, the results of biological experiments confirmed the antidepressant-like effects of embelin.Discussion These results indicated that embelin can effectively suppress CUS-induced depressive-like behaviors through increasing BDNF expression, preventing brain from oxidative stress and neuronal inflammation, and normalizing the HPA activity.

Liver X receptor β in the hippocampus: A potential novel target for the treatment of major depressive disorder?

Liver X receptors (LXRs), including LXRα and LXRβ isoforms, have been implicated in multiple physiological functions including promoting neurogenesis, improving synaptic plasticity, preventing neurodegeneration, inhibiting inflammation as well as regulating cholesterol metabolism. However, a potential role of LXRs in the treatment of major depressive disorder (MDD) has never been investigated previously. Our present results demonstrated that levels of hippocampal LXRβ but not LXRα were down-regulated in rats exposed to chronic unpredictable stress (CUS) and were negatively correlated with the severity of CUS-induced depressive-like behaviors. Furthermore, rats with LXRβ knockdown by short hairpin RNA (shRNA) in hippocampus displayed depressive-like behaviors and impaired hippocampal neurogenesis similar to those observed after CUS exposure. Conversely, LXRs activation by GW3965 (GW), a synthetic dual agonist for both LXRα and LXRβ isoforms, could improve depression-like behaviors and reverse the impaired hippocampal neurogenesis in rats exposed to CUS. LXRβ knockdown by shRNA completely abrogated the antidepressant and hippocampal neurogenesis-promoting effects of GW, suggesting that LXRβ isoform mediated the antidepressant and hippocampal neurogenesis-promoting effects of the LXRα/β dual agonist. However, ablation of hippocampal neurogenesis with x-irradiation only partly but not completely abolished the antidepressant effects of GW in the behavioral tests, implying that the antidepressant effects mediated by LXRβ isoform are likely through both neurogenesis-dependent and -independent pathways. Thus, our findings suggest that LXRβ activation may represent a potential novel target for the treatment of MDD and also provide a novel insight into the underlying mechanisms of MDD.

Uncoupling DAPK1 from NMDA receptor GluN2B subunit exerts rapid antidepressant-like effects

Several preclinical studies have reported the rapid antidepressant effects of N-methyl-D-aspartate receptor (NMDAR) antagonists, although the underlying mechanisms are still unclear. Death-associated protein kinase 1 (DAPK1) couples GluN2B subunits at extrasynaptic sites to regulate NMDAR channel conductance. In the present study, we found that chronic unpredictable stress (CUS) induced extracellular glutamate accumulation, accompanied by an increase in the DAPK1–NMDAR interaction, the high expression of DAPK1 and phosphorylated GluN2B at Ser1303, a decrease in phosphorylated DAPK1 at Ser308 and synaptic protein deficits in the rat medial prefrontal cortex (mPFC). CUS also enhanced GluN2B-mediated NMDA currents and extrasynaptic responses that were induced by bursts of high-frequency stimulation, which may be associated with the loss of astrocytes and low expression of glutamate transporter-1 (GLT-1). The blockade of GLT-1 in the mPFC was sufficient to induce depressive-like behavior and cause similar molecular changes. Selective GluN2B antagonist, DAPK1 knockdown by adeno-associated virus-mediated short-hairpin RNA or a pharmacological inhibitor, and the uncoupling of DAPK1 from the NMDAR GluN2B subunit produced rapid antidepressant-like effects and reversed CUS-induced alterations in the mPFC. The inhibition of DAPK1 and its interaction with GluN2B subunit in the mPFC also rescued CUS-induced depressive-like behavior 7 days after treatment. A selective GluN2B antagonist did not have rewarding effects in the conditioned place preference paradigm. Altogether, our findings suggest that the DAPK1 interaction with the NMDAR GluN2B subunit acts as a critical component in the pathophysiology of depression and is a potential target for new antidepressant treatments.

Acute agmatine administration, similar to ketamine, reverses depressive-like behavior induced by chronic unpredictable stress in mice

Agmatine is an endogenous neuromodulator that has been shown to have antidepressant-like properties. We have previously demonstrated that it can induce a rapid increase in BDNF levels after acute administration, suggesting that agmatine may be a fast-acting antidepressant. To investigate this hypothesis, the present study evaluated the effects of a single administration of agmatine in mice subjected to chronic unpredictable stress (CUS), a model of depression responsive only to chronic treatment with conventional antidepressants. The ability of agmatine to reverse CUS-induced behavioral and biochemical alterations was evaluated and compared with those elicited by the fast-acting antidepressant (ketamine) and the conventional antidepressant (fluoxetine). After exposed to CUS for 14days, mice received a single oral dose of agmatine (0.1mg/kg), ketamine (1mg/kg) or fluoxetine (10mg/kg), and were submitted to behavioral evaluation after 24h. The exposure to CUS caused an increased immobility time in the tail suspension test (TST) but did not change anhedonic-related parameters in the splash test. Our findings provided evidence that, similarly to ketamine, agmatine is able to reverse CUS-induced depressive-like behavior in the TST. Western blot analyses of prefrontal cortex (PFC) demonstrated that mice exposed to CUS and/or treated with agmatine, fluoxetine or ketamine did not present alterations in the immunocontent of synaptic proteins [i.e. GluA1, postsynaptic density protein 95 (PSD-95) and synapsin]. Altogether, our findings indicate that a single administration of agmatine is able to reverse behavioral alterations induced by CUS in the TST, suggesting that this compound may have fast-acting antidepressant-like properties. However, there was no alteration in the levels of synaptic proteins in the PFC, a result that need to be further investigated in other time points.

CX3CR1 (fractalkine receptor)-deficient mice exhibit resilience to chronic unpredictable stress-induced depressive-like behavior and suppressed neurogenesis

We recently demonstrated that microglia undergo dynamic alterations in activation state during the development of chronic unpredictable stress (CUS)-induced depressive-like behavior in mice. Moreover, manipulations of microglial activation, which counteracted these dynamic alternations, reversed the depressive-like behavioral symptoms. Here, we sought to determine whether CX3CR1-deficient mice, which display a mildly activated microglial phenotype, show increased or decreased sensitivity to CUS-induced depressive-like behavior. Experiments were conducted on homozygous mice with microglia-specific transgenic expression of GFP under the CX3CR1 promoter, in which the CX3CR1 gene was functionally deleted, and their C57BL wild-type (WT) controls. We found that following five weeks of CUS exposure, microglia numbers were significantly reduced in the hippocampal dentate gyrus (DG), but not CA3 region, in both WT and CX3CR1-deficient mice. However, only CUS-exposed WT mice showed a significant reduction in microglia soma size compared to controls, indicating resistance of CX3CR1-deficient microglia to stress-induced morphological changes. In addition, only CUS-exposed WT mice showed reduced sucrose preference and impaired novel object recognition memory, suggesting that CX3CR1-deficient mice do not exhibit CUS-induced depressive-like behavior, and show superior memory functioning under stress. Finally, doublecortin immunostaining of the DG revealed that exposure to CUS decreased neurogenesis in WT but not in CX3CR1-deficient mice. We conclude that CX3CR1 deficiency, which is associated with a mildly activated microglial phenotype, confers resilience to CUS-induced microglial alterations, depressive-like behavior, a nd suppressed neurogenesis.

SIRT2 is involved in the modulation of depressive behaviors.

Exposure to chronic stress produces negative effects on mood and hippocampus-dependent memory formation. SIRT2 alteration has been reported in mood disorders; however, the role of SIRT2 in depression remains unclear. Therefore, we aimed to determine whether SIRT2 can restore stress-induced suppression of neurogenesis in a rat chronic unpredictable stress (CUS) model of depression. Sucrose preference test, home-cage locomotion, forced swim test, and elevated plus maze were used to determine the role of SIRT2 in CUS model. To further determine the hippocampal neurogenesis contributes to the role of SIRT in mediating the antidepressant-like behavior, rats were exposed to X-irradiation to disrupt the process of hippocampal neurogenesis. CUS decreased expression of the SIRT2 protein in the hippocampus. Treatment with the antidepressant fluoxetine reversed the CUS-induced SIRT2 change. Furthermore, inhibiting SIRT2 by tenovin-D3 resulted in depression-like behaviors and impaired hippocampal neurogenesis in rats. Conversely, overexpression of SIRT2 by the intra-hippocampal infusion of recombinant adenovirus vector expressing mouse SIRT2 reversed the CUS-induced depressive-like behaviors, and promoted neurogenesis. Disrupting neurogenesis in the dentate gyrus by X-irradiation abolished the antidepressant-like effect of Ad-SIRT2-GFP. These findings indicate that hippocampal SIRT2 is involved in the modulation of depressant-like behaviors, possibly by regulating neurogenesis.

Antidepressant-like effects of a novel 5-HT3 receptor antagonist 6z in acute and chronic murine models of depression.

To investigate the antidepressant-like effects of a novel 5-HT3 receptor antagonist N-(benzo[d]thiazol-2-yl)-3-methoxyquinoxalin-2-carboxamide (6z) in acute and chronic murine models of depression. 5-HT3 receptor antagonism was examined in guinea pig ileum in vitro. A tail suspension test (TST) was used as acute depression model to evaluate the antidepressant-like behavior in mice treated with 6z (0.5-2 mg/kg, ip). In chronic depression model, mice were exposed to a 4-week chronic unpredictable stress (CUS) protocol, and treated with 6z (0.5-2 mg·kg(-1)·d(-1), po) or a positive drug fluoxetine (10 mg·kg(-1)·d(-1), po) in the last 2 weeks, followed by behavioral and biochemical assessments. The 5-HT3 receptor antagonism of 6z (pA2=7.4) in guinea pig ileum was more potent than that of a standard 5-HT3 receptor antagonist ondansetron (pA2=6.9). In acute depression model, 6z administration significantly decreased the immobility duration. In chronic depression model, 6z administration reversed CUS-induced depressive-like behavior, as evidenced by increased immobility duration in the forced swim test and sucrose preference in the sucrose preference test. Furthermore, chronic administration of 6z prevented CUS-induced brain oxidative stress, with significant reduction of pro-oxidant markers and elevation of antioxidant enzyme activity. Moreover, chronic administration of 6z attenuated CUS-induced hypothalamic-pituitary-adrenal axis hyperactivity, as shown by reduced plasma corticosterone levels. Similar results were observed in the fluoxetine-treated group. 6z is a novel 5-HT3 receptor antagonist with potential antidepressant-like activities, which may be related to modulating hypothalamic-pituitary-adrenal axis and attenuating brain oxidative damage.

Dynamic microglial alterations underlie stress-induced depressive-like behavior and suppressed neurogenesis

The limited success in understanding the pathophysiology of major depression may result from excessive focus on the dysfunctioning of neurons, as compared with other types of brain cells. Therefore, we examined the role of dynamic alterations in microglia activation status in the development of chronic unpredictable stress (CUS)-induced depressive-like condition in rodents. We report that following an initial period (2-3 days) of stress-induced microglial proliferation and activation, some microglia underwent apoptosis, leading to reductions in their numbers within the hippocampus, but not in other brain regions, following 5 weeks of CUS exposure. At that time, microglia displayed reduced expression of activation markers as well as dystrophic morphology. Blockade of the initial stress-induced microglial activation by minocycline or by transgenic interleukin-1 receptor antagonist overexpression rescued the subsequent microglial apoptosis and decline, as well as the CUS-induced depressive-like behavior and suppressed neurogenesis. Similarly, the antidepressant drug imipramine blocked the initial stress-induced microglial activation as well as the CUS-induced microglial decline and depressive-like behavior. Treatment of CUS-exposed mice with either endotoxin, macrophage colony-stimulating factor or granulocyte-macrophage colony-stimulating factor, all of which stimulated hippocampal microglial proliferation, partially or completely reversed the depressive-like behavior and dramatically increased hippocampal neurogenesis, whereas treatment with imipramine or minocycline had minimal or no anti-depressive effects, respectively, in these mice. These findings provide direct causal evidence that disturbances in microglial functioning has an etiological role in chronic stress-induced depression, suggesting that microglia stimulators could serve as fast-acting anti-depressants in some forms of depressive and stress-related conditions.

43. The role of dynamic microglial alterations in stress-induced depression and suppressed neurogenesis

Studies on the biological basis of major depression usually focus on abnormalities in neuronal functions. Glia cells, particularly astrocytes, have also been implicated in the pathophysiology of depression, however the role of microglia in this disease is still elusive. To elucidate the involvement of microglia in depression we examined the role of dynamic alterations in microglia activation status on the development of chronic unpredictable stress (CUS)-induced depressive-like condition in rodents. We report that following an initial period (2–3 days) of stress-induced microglial activation (reflected by proliferation, assumption of activated morphology and mRNA expression of activation markers), some microglia underwent apoptosis (reflected by activated caspase-3 and TUNEL staining), leading to reductions in their numbers within the hippocampus (but not in other brain regions) following 5-weeks of CUS exposure. At that time, microglia displayed reduced expression of activation markers as well as dystrophic morphology. The effects of CUS on microglia were blocked by chronic treatment with the tricyclic antidepressant drug imipramine. Furthermore, blockade of the initial stress-induced microglia activation by the microglial inhibitor minocycline or by transgenic interleukin-1 receptor antagonist over-expression rescued the subsequent microglia apoptosis and decline, as well as the CUS-induced depressive-like behavior and suppressed neurogenesis. These findings provide direct causal evidence that disturbances in microglial functioning have an etiological role in chronic stress-induced depression.

Ascorbic acid treatment, similarly to fluoxetine, reverses depressive-like behavior and brain oxidative damage induced by chronic unpredictable stress

Reactive oxygen species (ROS) have been shown to play a role in the pathophysiology of depression. Taking into account that experimental chronic unpredictable stress (CUS) induces depressive-like behavior and that ascorbic acid has antidepressant-like effect in animals, the objective of this study was to investigate the influence of ascorbic acid on depressive-like behavior induced by CUS paradigm, serum corticosterone levels and markers of oxidative stress in cerebral cortex and hippocampus of mice. Animals were submitted to CUS procedure during 14 days. From the 8th to the 14th day mice received ascorbic acid (10 mg/kg) or fluoxetine (10 mg/kg, conventional antidepressant, positive control) once a day by oral route. On 15th day behavioral and biochemical parameters were analyzed. CUS exposure caused a depressive-like behavior evidenced by the increased immobility time in the tail suspension test and decreased time in which mice spent grooming in the splash test. Depressive-like behavior induced by CUS was accompanied by a significant increased lipid peroxidation (cerebral cortex and hippocampus), decreased catalase (CAT) (cerebral cortex and hippocampus) and glutathione reductase (GR) (hippocampus) activities and reduced levels of glutathione (cerebral cortex). Repeated ascorbic acid or fluoxetine administration significantly reversed CUS-induced depressive-like behavior and oxidative damage. No alteration was observed in locomotor activity, corticosterone levels and glutathione peroxidase (GPx) activity. These findings indicate a rapid and robust effect of ascorbic acid in reversing behavioral and biochemical alterations induced by CUS in mice, suggesting that this vitamin may be an alternative approach for the management of depressive symptoms.

Clomipramine treatment reversed the glial pathology in a chronic unpredictable stress-induced rat model of depression

Growing evidence indicates that glia pathology contributes to the pathophysiology and possibly the etiology of depression. The study investigates changes in behaviors and glial fibrillary associated protein (GFAP) in the rat hippocampus after chronic unpredictable stress (CUS), a rat model of depression. Furthermore, we studied the effects of clomipramine, one of tricyclic antidepressants (TCAs), known to modulate serotonin and norepinephrine uptake, on CUS-induced depressive-like behaviors and GFAP levels. Rats exposed to CUS showed behavioral deficits in physical state, open field test and forced swimming test and exhibited a significant decrease in GFAP expression in the hippocampus. Interestingly, the behavioral and GFAP expression changes induced by CUS were reversed by chronic treatment with the antidepressant clomipramine. The beneficial effects of clomipramine treatment on CUS-induced depressive-like behavior and GFAP expression provide further validation of our hypothesis that glial dysfunction contributes to the pathophysiology of depression and that glial elements may represent viable targets for new antidepressant drug development.