Unpredictable Chronic Mild Stress Procedure Research Articles

The gut microbiota metabolite indole increases emotional responses and adrenal medulla activity in chronically stressed male mice

Background and aimsThe gut microbiota produces metabolites that are an integral part of the metabolome and, as such, of the host physiology. Changes in gut microbiota metabolism could therefore contribute to pathophysiological processes. We showed previously that a chronic and moderate overproduction of indole from tryptophan in male individuals of the highly stress-sensitive F344 rat strain induced anxiety-like and helplessness behaviors. The aim of the present study was to extend the scope of these findings by investigating whether emotional behaviors of male mice that are moderately stress-sensitive but chronically exposed to environmental stressors would also be affected by indole. MethodsWe colonized germ-free male C3H/HeN mice with a wild-type indole-producing Escherichia coli strain, or with the non-indole producing mutant. Gnotobiotic mice were subjected to an unpredictable chronic mild stress procedure, then to a set of tests aimed at assessing anxiety-like (novelty and elevated plus maze tests) and depression-like behaviors (coat state, splash, nesting, tail suspension and sucrose tests). Results of the individual tests were aggregated into a common z-score to estimate the overall emotional response to chronic mild stress and chronic indole production. We also carried out biochemical and molecular analyses in gut mucosa, plasma, brain hippocampus and striatum, and adrenal glands, to examine biological correlates that are usually associated with stress, anxiety and depression. ResultsChronic mild stress caused coat state degradation and anhedonia in both indole-producing and non-indole producing mice, but it did not influence behaviors in the other tests. Chronic indole production did not influence mice behavior when tests were considered individually, but it increased the overall emotionality z-score, specifically in mice under chronic mild stress. Interestingly, in the same mice, indole induced a dramatic increase of the expression of the adrenomedullary Pnmt gene, which is involved in catecholamine biosynthesis. By contrast, systemic tryptophan bioavailability, brain serotonin and dopamine levels and turnover, as well as expression of gut and brain genes involved in cytokine production and tryptophan metabolism along the serotonin and kynurenine pathways, remained similar in all mice. ConclusionsChronic indole production by the gut microbiota increased the vulnerability of male mice to the adverse effects of chronic mild stress on emotional behaviors. It also targeted catecholamine biosynthetic pathway of the adrenal medulla, which plays a pivotal role in body’s physiological adaptation to stressful events. Future studies will aim to investigate the action mechanisms responsible for these effects.

Exploration of the antidepressant‐like effect of repeated administration of Nigella fixed oil in rats

Due to the confirmation of the therapeutic properties of oils extracted from Nigella, and the constraints associated with antidepressant prescriptions, the reliance on phototherapy seems to be beneficial. The objective of the present paper is to investigate the behavioral effect of Nigella fixed oil, as well as exploring the histopathological impact on the structure of the hippocampus after exposure to the Unpredictable Chronic Mild Stress procedure in rats.Animals were randomly divided into five groups of eight. The stress procedure used in this study combines many stressful situations. These situations were randomly assigned with a frequency of two stressors per day throughout the 5‐weeks. Behavioral evaluation of antidepressant activity was based on the forced swimming test and histological evaluation of the hippocampus of rats with optical microscopy.Treatment by nigella and fluoxetine significantly reduces the struggling time during the test day of the forced swim test. Histopathological analysis showed that control treatments result in more loosely arranged cells, significant apoptotic neurons characterized by an irregular appearance, and pyknotic hyperchromatic. As well as a reduction in the thickness of the pyramid layer compared to the groups treated with nigella and fluoxetine.The results demonstrated the effect of Nigella in the forced swimming test, as well as the improvement of the pyramidal cell organization and neuronal degeneration. These data seem to be consistent with other studies, in which the neuroprotective properties of nigella refer to thymoquinone.

Saikosaponin D relieves unpredictable chronic mild stress induced depressive-like behavior in rats: involvement of HPA axis and hippocampal neurogenesis.

Saikosaponin D (SSD), a major bioactive component isolated from Radix Bupleuri, has been reported to exert neuroprotective properties. The present study was designed to investigate the anti-depressant-like effects and the potential mechanisms of SSD. Behavioural tests including sucrose preference test (SPT), open field test (OFT) and forced swim test (FST) were performed to study the antidepressant-like effects of SSD. In addition, we examined corticosterone and glucocorticoid receptor (GR) levels to evaluate hypothalamic-pituitary-adrenal (HPA) axis function. Furthermore, hippocampal neurogenesis was assessed by testing doublecortin (DCX) levels, and neurotrophic molecule levels were also investigated in the hippocampus of rats. We found that unpredictable chronic mild stress (UCMS) rats displayed lost body weight, decreased sucrose consumption in SPT, reduced locomotive activity in OFT, and increased immobility time in FST. Chronic treatment with SSD (0.75, 1.50mg/kg) remarkably ameliorated the behavioral deficiency induced by UCMS procedure. SSD administration downregulated elevated serum corticosterone levels, as well as alleviated the suppression of GR expression and nuclear translocation caused by UCMS, suggesting that SSD is able to remit the dysfunction of HPA axis. In addition, Western blot and immunohistochemistry analysis showed that SSD treatment significantly increased the generation of neurons in the hippocampus of UCMS rats indicated by elevated DCX levels. Moreover, hippocampal neurotrophic molecule levels of UCMS rats such as phosphorylated cAMP response element binding protein (p-CREB) and brain-derived neurotrophic factor (BDNF) were raised after SSD treatment. Together, Our results suggest that SSD opposed UCMS-induced depressive behaviors in rats, which was mediated, partially, by the enhancement of HPA axis function and consolidation of hippocampal neurogenesis.

P.4.c.003 - Agomelatine reverses cognition-related behavior and hippocampal gene expression alterations induced by chronic social defeat stress in mice

Depression is recognized as a predictor of increased cardiac morbidity and mortality. In addition, depressed patients exhibit an increase in the serum markers of endothelial dysfunction and platelet activation involved in the cascade of events leading to atherosclerosis. The purpose of this study was to determine the early and late-onset expression of various vascular markers in a rodent model of depression. Male DBA (an inbred strain of mice)/2J mice were exposed to either 7 weeks of controlled living conditions or unpredictable chronic mild stress (UCMS), and subsequently given daily fluoxetine (10 mg/kg) or NaCl (9%) during the last 5 weeks of the experiment. Depressive-like behavior was evaluated by using motivational and self-care behavior, including the assessment of the animal's coat state and grooming behavior. Enzyme-linked immunoassay was used to quantify matrix metalloproteinase-9 (MMP-9), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and plasminogen activator inhibitor-1 (PAI-1) expression either immediately after the end of the UCMS procedure (short term condition) or 10 months later (long-term condition). Results indicate that 1) UCMS procedure induces a short-term depressive-like behavior in mice, defined as coat state deterioration, an effect that is prevented by fluoxetine treatment; 2) UCMS procedure has no effect on the short-term expression of the studied markers; however, UCMS increases expression of plasminogen activator inhibitor-1 only in the long-term group; 3) fluoxetine treatment is unable to counteract this UCMS-induced change; 4) aging induces behavioral perturbation, defined as a decrease in grooming motivation, and an increase of all the vascular markers in both control and UCMS groups and 5) pretreatment with fluoxetine has no protective effects on aging-induced behavioral and vascular alterations. Thus, in this model of depression-like behavior, UCMS appears to induce late-onset physiological changes, which are consistent with human studies indicating that depression is a risk factor for the development of heart disease.

Antidepressant-like effects of water extract of Gastrodia elata Blume in rats exposed to unpredictable chronic mild stress via modulation of monoamine regulatory pathways

Ethnopharmacology relevanceGastrodia elata Blume (GE) is a traditional herbal medicine belonging to the Orchidaceae family, and has been used to manage neurological disorders for centuries. We have previously reported that its water extract (WGE) could improve the depressive-like behaviours in the forced swimming test (FST), an animal model of depression. Aim of the studyTo investigate the antidepressant-like effects of WGE in rats exposed to unpredictable chronic mild stress (UCMS) model, and to explore its possible molecular mechanisms. Materials and methodsUCMS rats were orally administered with WGE (0.5g/kg body weight) daily within the 4 weeks UCMS procedure. The sucrose preference test and the open field test were conducted to assess anhedonia and spontaneous behaviours, respectively. The cerebral turnover rates of monoamine neurotransmitters and the serum corticosterone levels were measured. In vitro direct and indirect monoamine oxidase A (MAO-A) inhibitory assays were employed to assess the possible antidepressant-like mechanisms of WGE (0.5mg/mL) and its major component, gastrodin (GAS, 15, 30 and 60μg/mL). Western blot was used to examine the expression of protein related to monoamine regulation, such as MAO-A and tyrosine hydroxylase (TH). ResultsWGE significantly reversed the sucrose preference and other abnormal behaviours induced by 4 weeks of UCMS. WGE significantly restored the cerebral turnover rates of serotonin and dopamine and decreased serum corticosterone levels. WGE and gastrodin inhibited the activity and protein expression of MAO-A, and increased TH levels in PC12 cells. ConclusionThe antidepressant-like effects of WGE and gastrodin might be mediated by the regulation of monoamine neurotransmitters, and therefore were beneficial in depression treatment as a complementary approach.

Antidepressant‐Like Activity of Agomelatine in the Mouse Unpredictable Chronic Mild Stress Model

Preclinical Research The present study was undertaken to investigate whether chronic agomelatine treatment which acts as an agonist of melatonergic MT1 and MT2 receptors would block unpredictable chronic mild stress (UCMS)-induced depression-like behavior in mice as compared with fluoxetine and melatonin. Male inbred BALB/c mice were treated with agomelatine (10 mg/kg i.p.), melatonin (10 mg/kg ip), fluoxetine (15 mg/kg ip), or vehicle for 5 weeks. All compounds tested blocked the stress-induced deficit in coat state during the UCMS procedure, increased total latency of grooming in the splash test, decreased attack frequency in the resident/intruder test, and reduced immobility time in the tail suspension and forced swimming tests. All compounds also reduced the levels of plasma adrenocorticotropic hormone, interleukin 6, and tumor necrosis factor-alpha in stressed mice. The results of this study indicate that agomelatine, which has a novel mode of action, can be as effective as fluoxetine for the treatment of depression.

Antidepressant‐Like Activity of Agomelatine in the Mouse Unpredictable Chronic Mild Stress Model

Abstract Preclinical Research The present study was undertaken to investigate whether chronic agomelatine treatment which acts as an agonist of melatonergic MT1 and MT2 receptors would block unpredictable chronic mild stress (UCMS)‐induced depression‐like behavior in mice as compared with fluoxetine and melatonin. Male inbred BALB/c mice were treated with agomelatine (10 mg/kg i.p.), melatonin (10 mg/kg ip), fluoxetine (15 mg/kg ip), or vehicle for 5 weeks. All compounds tested blocked the stress‐induced deficit in coat state during the UCMS procedure, increased total latency of grooming in the splash test, decreased attack frequency in the resident/intruder test, and reduced immobility time in the tail suspension and forced swimming tests. All compounds also reduced the levels of plasma adrenocorticotropic hormone, interleukin 6, and tumor necrosis factor‐alpha in stressed mice. The results of this study indicate that agomelatine, which has a novel mode of action, can be as effective as fluoxetine for the treatment of depression.

Antidepressant-like effect of flaxseed secoisolariciresinol diglycoside in ovariectomized mice subjected to unpredictable chronic stress

Secoisolariciresinol diglycoside (SDG), a predominant lignan in flaxseed, has antioxidant activity as a dietary supplement. The purpose of the present study was to investigate the antidepressant-like effect and the possible mechanism of flaxseed SDG when the ovariectomized mice were exposed to the unpredictable chronic mild stress procedure. Chronic stress induced the increases in immobility time in mouse model of despair tests, but administration with SDG (80 and 160 mg/kg, p.o.) for 21 days inhibited these behavioral changes caused by stress in both forced swimming and tail suspension tests. These doses that affected the immobile response did not affect locomotor activity. Moreover, the changes in the serum corticosterone and adrenocorticotropic hormone (ACTH) levels were also measured to explore the SDG-associated regulation of hypothalamus-pituitary-adrenals (HPA) axis. The results indicated that the chronic stress-induced increases in the serum corticosterone and ACTH were reversed by treatment with high doses of SDG. Chronic treatment with SDG also affected the body weight of mice and IL-6, IL1β levels in the frontal cortex. In addition, chronic stress procedure induced a decrease in brain-derived neurotrophic factor (BDNF) expression in the frontal cortex of mice; while treatment with SDG reversed this reduction of BDNF. All these results provide compelling evidence that the behavioral effects of flaxseed SDG in the ovariectomized mice might be related to their modulating effects on the neuroendocrine-immune network and neurotrophin factor expression.

Effects of fluoxetine, tianeptine and olanzapine on unpredictable chronic mild stress-induced depression-like behavior in mice

AimsTianeptine is an atypical antidepressant drug that has a different mechanism of action than other antidepressants. Olanzapine is an atypical antipsychotic drug used for the treatment of schizophrenia. The present study was undertaken to investigate effects of chronic administration of tianeptine or olanzapine on unpredictable chronic mild stress (UCMS)-induced depression-like behavior in mice compared to a widely used SSRI antidepressant, fluoxetine. Main methodsMale inbred BALB/c mice were subjected to different kinds of stressors several times a day for 7weeks and were treated intraperitoneally with tianeptine (5mg/kg), olanzapine (2.5mg/kg), fluoxetine (15mg/kg) or vehicle for 5weeks (n=7–8 per group). Key findingsAll the drugs tested prevented stress-induced deficit in coat state during UCMS procedure, in grooming behavior in the splash test, decreased the attack frequency in the resident intruder test and decreased the immobility time in the tail suspension test. In the open field test olanzapine had anxiolytic-like effects in both stressed and non-stressed mice. Tianeptine, olanzapine and fluoxetine decreased the enhanced levels of plasma ACTH and IL-6. Chronic treatment with tianeptine resulted in a significant increase in both total number and density of BrdU-labeled cells in stressed animals, while fluoxetine and olanzapine had a partial effect. SignificanceThe results of this study support the hypothesis that tianeptine can be as effective as fluoxetine for the treatment of depression in spite of the differences in the mechanism of action of these drugs. Moreover, olanzapine could be used effectively in psychotic patients with depression.

P.2.d.002 An atypical antidepressant tianeptine prevents unpredictable chronic mild stress-induced depressive effects in mice

Tianeptine is an atypical antidepressant drug that has a different mechanism of action than other antidepressants. Olanzapine is an atypical antipsychotic drug used for the treatment of schizophrenia. The present study was undertaken to investigate effects of chronic administration of tianeptine or olanzapine on unpredictable chronic mild stress (UCMS)-induced depression-like behavior in mice compared to a widely used SSRI antidepressant, fluoxetine.Male inbred BALB/c mice were subjected to different kinds of stressors several times a day for 7 weeks and were treated intraperitoneally with tianeptine (5 mg/kg), olanzapine (2.5 mg/kg), fluoxetine (15 mg/kg) or vehicle for 5 weeks (n = 7–8 per group).All the drugs tested prevented stress-induced deficit in coat state during UCMS procedure, in grooming behavior in the splash test, decreased the attack frequency in the resident intruder test and decreased the immobility time in the tail suspension test. In the open field test olanzapine had anxiolytic-like effects in both stressed and non-stressed mice. Tianeptine, olanzapine and fluoxetine decreased the enhanced levels of plasma ACTH and IL-6. Chronic treatment with tianeptine resulted in a significant increase in both total number and density of BrdU-labeled cells in stressed animals, while fluoxetine and olanzapine had a partial effect.The results of this study support the hypothesis that tianeptine can be as effective as fluoxetine for the treatment of depression in spite of the differences in the mechanism of action of these drugs. Moreover, olanzapine could be used effectively in psychotic patients with depression.

Early and Late-Onset Effect of Chronic Stress on Vascular Function in Mice: A Possible Model of the Impact of Depression on Vascular Disease in Aging

Depression is recognized as a predictor of increased cardiac morbidity and mortality. In addition, depressed patients exhibit an increase in the serum markers of endothelial dysfunction and platelet activation involved in the cascade of events leading to atherosclerosis. The purpose of this study was to determine the early and late-onset expression of various vascular markers in a rodent model of depression. Male DBA (an inbred strain of mice)/2J mice were exposed to either 7 weeks of controlled living conditions or unpredictable chronic mild stress (UCMS), and subsequently given daily fluoxetine (10 mg/kg) or NaCl (9%) during the last 5 weeks of the experiment. Depressive-like behavior was evaluated by using motivational and self-care behavior, including the assessment of the animal's coat state and grooming behavior. Enzyme-linked immunoassay was used to quantify matrix metalloproteinase-9 (MMP-9), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and plasminogen activator inhibitor-1 (PAI-1) expression either immediately after the end of the UCMS procedure (short term condition) or 10 months later (long-term condition). Results indicate that 1) UCMS procedure induces a short-term depressive-like behavior in mice, defined as coat state deterioration, an effect that is prevented by fluoxetine treatment; 2) UCMS procedure has no effect on the short-term expression of the studied markers; however, UCMS increases expression of plasminogen activator inhibitor-1 only in the long-term group; 3) fluoxetine treatment is unable to counteract this UCMS-induced change; 4) aging induces behavioral perturbation, defined as a decrease in grooming motivation, and an increase of all the vascular markers in both control and UCMS groups and 5) pretreatment with fluoxetine has no protective effects on aging-induced behavioral and vascular alterations. Thus, in this model of depression-like behavior, UCMS appears to induce late-onset physiological changes, which are consistent with human studies indicating that depression is a risk factor for the development of heart disease.

Evidence for a key role of the peripheral kynurenine pathway in the modulation of anxiety- and depression-like behaviours in mice: Focus on individual differences

We previously reported that confronting mice to the Unpredictable Chronic Mild Stress procedure (UCMS) resulted in peripheral and cerebral alterations of the kynurenine pathway (KP). The present study tested whether KP disturbances are associated with differences in anxiety- and depressive-like behaviors in both naïve and UCMS mice. Non-stressed and UCMS mice were subjected to the elevated plus maze test and to the forced swim test. Mice were then sacrificed for quantification of tryptophan (TRP)-serotonin (5-HT) and TRP-kynurenine (KYN) metabolites in two corticolimbic structures involved in the regulation of mood (cingulate cortex=CC; amygdala=AMY). We showed that an elevated peripheral (lung) KYN/TRP ratio is correlated to the magnitude of anxiodepressive-like phenotypes only in UCMS mice. We also observed, in UCMS mice, that a high peripheral (lung) KYN/TRP ratio is associated with an increased metabolism of 5-HT in CC and a reduced level of kynurenic acid (KYNA) in AMY. Our results suggest that elevated peripheral KP might underlie cerebral biochemical changes and might consequently be involved in the modulation of behavior but only in UCMS mice. These findings make more complete the comprehension of the KP involvement in behavioral changes induced by chronic stress and suggest that it could play a crucial role in the modulation of emotional states.

Effects of neuronal and inducible NOS inhibitor 1-[2-(trifluoromethyl) phenyl] imidazole (TRIM) in unpredictable chronic mild stress procedure in mice

Nitric oxide is an intracellular messenger which is involved in several functions and pathologies such as depression, anxiety, learning and memory. In many studies nitric oxide synthase inhibitors (NOSI) were shown to possess antidepressant-like effects in animal models of depression. The aim of this study is to investigate the effects of a selective neuronal and inducible nitric oxide synthase inhibitor TRIM (30 mg/kg/day, 35 days) in mice subjected to unpredictable chronic mild stress and then compare it's effect with a conventional selective serotonin reuptake inhibitor fluoxetine (15 mg/kg/day, 35 days). Stressed vehicle animals showed a significant disturbed coat state when compared with nonstressed animals and this effect was reversed by TRIM or fluoxetine. Both TRIM and fluoxetine prevented the stress-induced deficit in the grooming behaviour in the splash test. TRIM and fluoxetine also significantly decreased the attack frequency when compared to the stressed control group in the resident–intruder test. These results support the assumption that NOS inhibitors can be a new class of antidepressant drugs possibly acting on neuronal NOS.

Antidepressant-like effect of tramadol in the unpredictable chronic mild stress procedure: possible involvement of the noradrenergic system

Tramadol, which inhibits the reuptake of noradrenaline and serotonin, is effective in animal models of depression. Its antidepressant-like effects may be mediated mainly by the noradrenergic system. This study investigated the role of the noradrenergic system in the antidepressant-like effects of tramadol and desipramine in the unpredictable chronic mild stress model. We assessed the involvement of beta-adrenoreceptors, particularly beta2-receptors in the activity of these drugs. In addition, we measured the level of noradrenaline and its metabolite 3-methoxy-4-hydroxy-phenylglycol (MHPG) in the locus coeruleus, hypothalamus, hippocampus and cerebellum in stressed mice. Unpredictable chronic mild stress induced a degradation of coat state and decreased grooming behaviour in the splash test, which was reversed by the chronic administration of tramadol (20 mg/kg) and desipramine (10 mg/kg). The nonselective beta-adrenoreceptor antagonist propranolol (5 mg/kg, intraperitoneally) and the selective beta2-receptor antagonist ICI 118,551 (2 mg/kg, intraperitoneally) reversed the antidepressant-like effects of tramadol and desipramine. Moreover, chronic tramadol and desipramine treatment increased the level of noradrenaline (NA) and MHPG in the locus coeruleus but not in the cerebellum, whereas only MHPG level was increased in the hypothalamus. Tramadol, however, increased the levels of MHPG and NA in the hippocampus, whereas desipramine only increased NA level. These data support the view that the noradrenergic system plays an important role in the antidepressant-like action of tramadol.