Chronic Unpredictable Mild Stress Treatment Research Articles

Sub-anesthetic doses of ketamine exert antidepressant-like effects and upregulate the expression of glutamate transporters in the hippocampus of rats

Clinical studies on the role of the glutamatergic system in the pathogenesis of depression found that ketamine induces an antidepressant response, but the molecular mechanisms remain unclear. The present study investigated the effects of sub-anesthetic doses of ketamine on the glutamate reuptake function in the rat hippocampus. Chronic unpredictable mild stress (CUMS) was applied to construct animal models of depression. Sixty adult male Sprague-Dawley rats were randomly assigned to 5 groups and received a different regimen of CUMS and ketamine (10, 25, and 50mg/kg) treatment. The sucrose preference test and open-field test were used to assess behavioral changes. The expression levels of excitatory amino acid transporters (EAATs) were measured by western blot. Microdialysis and high-performance liquid chromatography (HPLC) were used to detect hippocampal glutamate concentrations. We found that the expression of EAAT2 and EAAT3 were obviously downregulated, and extracellular concentrations of glutamate were significantly increased in the hippocampi of depressive-like rats. Ketamine (10, 25, and 50mg/kg) upregulated the expression of EAAT2 and EAAT3, decreased the hippocampal concentration of extracellular glutamate, and alleviated the rats’ depressive-like behavior. The antidepressant effect of ketamine may be linked to the regulation of EAAT expression and the enhancement of glutamate uptake in the hippocampus of depressive-like rats.

Chronic Unpredictable Mild Stress Induces Loss of GABA Inhibition in Corticotrophin-Releasing Hormone-Expressing Neurons through NKCC1 Upregulation

Introduction: Prolonged and repeated stresses cause hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. The corticotrophin-releasing hormone (CRH)-expressing neurons in the hypothalamic paraventricular nucleus (PVN) are an essential component of the HPA axis. Materials and Methods: Chronic unpredictable mild stress (CUMS) was induced in Sprague-Dawley rats. GABA reversal potentials (E_GABA) were determined by using gramicidin-perforated recordings in identified PVN-CRH neurons through expressing enhanced green fluorescent protein driven by the CRH promoter. Plasma corticosterone (CORT) levels were measured in rats implanted with a cannula targeting the lateral ventricles and PVN. Results: Blocking the GABA_A receptor in the PVN with gabazine significantly increased plasma CORT levels in unstressed rats but did not change CORT levels in CUMS rats. CUMS caused a depolarizing shift in E_GABA in PVN-CRH neurons compared with E_GABA in PVN-CRH neurons in unstressed rats. Furthermore, CUMS induced a long-lasting increase in expression levels of the cation chloride cotransporter Na⁺-K⁺-Cl^--Cl^- (NKCC1) in the PVN but a transient decrease in expression levels of K⁺-Cl^--Cl^- in the PVN, which returned to the basal level 5 days after CUMS treatment. The NKCC1 inhibitor bumetanide decreased the basal firing activity of PVN-CRH neurons and normalized E_GABA and the gabazine-induced excitatory effect on PVN-CRH neurons in CUMS rats. In addition, central administration of bumetanide decreased basal circulating CORT levels in CUMS rats. Conclusions: These data suggest that chronic stress impairs GABAergic inhibition, resulting in HPA axis hyperactivity through upregulation of NKCC1.

Role of hypothalamic cannabinoid receptors in post-stroke depression in rats.

One of the most common psychological consequences of stroke is post-stroke depression (PSD). While more than 30 percent of stroke patients eventually develop PSD, the neurobiological mechanisms underlying such a phenomenon have not been well investigated. Given the critical involvement of hypothalamic-pituitary-adrenal axis and endocannabinoid system in response to stressful stimuli, we evaluated the hypothesis that cannabinoid receptors in the hypothalamus are critical for modulation of post-stroke depression-like behaviors in rats. To this end, rats were treated with middle cerebral artery occlusion (MCAO) followed by chronic unpredictable mild stress (CUMS) treatment procedure. We then assessed the expression of CB1 and CB2 receptors in the hypothalamus, and evaluated the effects of pharmacological stimulations of CB1 or CB2 receptors on the expression and development of depression-like behaviors in PSD rats. We found that PSD rats exhibited decreased the expression of CB1 receptor, but not CB2 receptor, in the ventral medial hypothalamus (VMH). Such an effect was not observed in the dorsally adjacent brain regions. Furthermore, intra-VMH injections of CB2 receptor agonist, but not CB1 receptor agonist, attenuated the expression of depression-like behaviors in PSD rats. Finally, repeated intraperitoneal injections of CB1 or CB2 receptor agonists during CUMS treatment inhibited the development of depression-like behaviors in PSD rats. Taken together, these results suggest that decreased CB1 receptor expression is likely associated with the development of post-stroke depression, and CB2 receptor may be a potential therapeutic target for the treatment post-stroke depressive disorders.

Loss of GABAergic Inhibition in Hypothalamus in Chronic Stress

Chronic stress increases activity of hypothalamic‐pituitary‐adrenal (HPA) axis. CRH‐expressing neuron in the PVN is an essential component of HPA axis and plays a critical role in stress response. The activity of CRH neurons is regulated by excitatory and inhibitory GABAergic synaptic inputs. We hypothesized that chronic stress diminishes GABAergic inhibition, which contributes to hyperactivity of PVN‐CRH neurons. We identified PVN‐CRH neurons by expressing green fluorescent protein (GFP) driven by CRH promoter. Chronic unpredictable mild stress (CUMS) significantly increased plasma corticosterone levels. Blocking GABAA receptor significantly increased plasma corticosterone levels in unstressed rats. Furthermore, it significantly increased firing activity of PVN‐CRH neurons in unstressed rats but did not significant change in CUMS rats, while GABAA receptor significantly decreased firing activity of PVN‐CRH neurons in unstressed rats but slightly increased in CUMS rats. CUMS treatment significantly increased Na+‐K+‐2Cl‐ cotransporter (NKCC1) protein and mRNA levels while decreased K+‐2Cl‐ (KCC2) protein and mRNA levels in the PVN tissue. Immunocytochemical staining showed that they are expressed on CRH immunoreactivity positive PVN neurons. In addition, treatment with NKCC1 specific inhibitor decreased the basal firing activity of PVN‐CRH neurons in CUMS rats, but not in unstressed rats. Furthermore, it restored gabazine‐induced excitatory effect on PVN‐CRH neurons in CUMS rats. These data suggest that GABAergic inhibition in the PVN is diminished due to upregulation of NKCC1 in chronic stress.

Integration of 1H NMR and UPLC-Q-TOF/MS for a Comprehensive Urinary Metabonomics Study on a Rat Model of Depression Induced by Chronic Unpredictable Mild Stress

Depression is a type of complex psychiatric disorder with long-term, recurrent bouts, and its etiology remains largely unknown. Here, an integrated approach utilizing 1H NMR and UPLC-Q-TOF/MS together was firstly used for a comprehensive urinary metabonomics study on chronic unpredictable mild stress (CUMS) treated rats. More than twenty-nine metabolic pathways were disturbed after CUMS treatment and thirty-six potential biomarkers were identified by using two complementary analytical technologies. Among the identified biomarkers, nineteen (10, 11, 16, 17, 21–25, and 27–36) were firstly reported as potential biomarkers of CUMS-induced depression. Obviously, this paper presented a comprehensive map of the metabolic pathways perturbed by CUMS and expanded on the multitude of potential biomarkers that have been previously reported in the CUMS model. Four metabolic pathways, including valine, leucine and isoleucine biosynthesis; phenylalanine, tyrosine and tryptophan biosynthesis; tryptophan metabolism; synthesis and degradation of ketone bodies had the deepest influence in the pathophysiologic process of depression. Fifteen potential biomarkers (1–2, 4–6, 15, 18, 20–23, 27, 32, 35–36) involved in the above four metabolic pathways might become the screening criteria in clinical diagnosis and predict the development of depression. Moreover, the results of Western blot analysis of aromatic L-amino acid decarboxylase (DDC) and indoleamine 2, 3-dioxygenase (IDO) in the hippocampus of CUMS-treated rats indicated that depletion of 5-HT and tryptophan, production of 5-MT and altered expression of DDC and IDO together played a key role in the initiation and progression of depression. In addition, none of the potential biomarkers were detected by NMR and LC-MS simultaneously which indicated the complementary of the two kinds of detection technologies. Therefore, the integration of 1H NMR and UPLC-Q-TOF/MS in metabonomics study provided an approach to identify the comprehensive potential depression-related biomarkers and helpful in further understanding the underlying molecular mechanisms of depression through the disturbance of metabolic pathways.

Corticosterone reduces brain mitochondrial function and expression of mitofusin, BDNF in depression-like rodents regardless of exercise preconditioning

Both chronic mild stress and an injection of corticosterone induce depression-like states in rodents. To further link mitochondrial dysfunction to the pathophysiology of major depression, here we describe two rat models of a depressive-like state induced by chronic unpredictable mild stress (CUMS) or corticosterone treatment (CORT). It is also a model that allows the simultaneous study of effects of exercise preconditioning on behavioral, electrophysiological, biochemical and molecular markers in the same animal. Exercise preconditioning ahead of CUMS and CORT treatment prevents many behavioral abnormalities resulted from CUMS. The changes in mitochondrial activity in brain and reduced expressions of superoxide dismutase (SOD1, SOD2), mitofusin (Mfn1, Mfn2) as well as brain-derived neurotrophic factor (BDNF) suggest that both CORT and CUMS may impair mitochondrial function and/or expressions of mitofusion and antioxidant enzymes that, in turn, may increase oxidative stress and reduce energy production in brain with depression-like behaviors. These findings suggest an underlying mechanism by which CORT, as well as CUMS, induces brain mitochondrial dysfunction that is associated with depressive-like states. Remarkably, physical exercise is identified as a helpful and preventive measure to promote mitochondrial function and expressions of mitofusin, BDNF and antioxidant enzymes in brain, so as to protect brain energy metabolism against CUMS, rather than the compound of corticosterone.

Anti-depressant effects of Xiaoyaosan on rat model of chronic unpredictable mild stress: a plasma metabonomics study based on NMR spectroscopy

To investigate the antidepressant effects of Xiaoyaosan (XYS) in a chronic unpredictable mild stress (CUMS) depression model. The changes in behaviour and plasma metabolic profiles were investigated after four-week CUMS exposure and treatment. Drugs were administered during the four-week period of CUMS, with the healthy group serving as negative controls, and the fluoxetine and venlafaxine groups serving as positive controls. Plasma samples were collected at 28th day, and the plasma metabolic profiling was measured using NMR, followed by multivariate analysis. Exposure to CUMS for four weeks caused depression-like behaviour in rats, as indicated by significant decreases in weight gain, sucrose consumption and locomotor activity. Eleven potential biomarkers, including seven in the Carr-Purcell-Meiboom-Gill spectra, five in the diffusion-edited spectra, and one in both were identified. It was found that trimethylamine-N-oxide, alanine, β-hydroxybutyrate, valine, leucine/isoleucine, low-density lipoprotein/very low-density lipoprotein and lipids were lower and phosphatidylcholine, high-density lipoprotein, choline and N-acetyl glycoproteins were higher in CUMS-treated rats, as compared with controls. XYS significantly suppressed behavioural changes and attenuated plasma metabolite changes. XYS produced an obvious antidepressant effect, and the metabonomic approach benefits estimation of the pharmacodynamic action of traditional Chinese medicine prescriptions.

Study of plasma metabolic profiling and biomarkers of chronic unpredictable mild stress rats based on gas chromatography/mass spectrometry

A metabolomic investigation of chronic unpredictable mild stress (CUMS) rats was carried out. Plasma obtained from Sprague-Dawley (SD) rats treated by CUMS was analyzed using gas chromatography/mass spectrometry. Thirty-seven metabolites were identified among the detected compounds. Subsequent data analysis using the t test and principal component analysis (PCA) revealed significant metabolic changes in the rats' plasma after CUMS treatment. Clear separation between the model and control group was achieved, and the level of twelve metabolites, including amino acids, sugar, organic acids and fatty acids, were significantly different between plasma samples from the controls and CUMS group. These observations suggested that the depressed state may be associated with perturbation of amino acid metabolism, energy metabolism and glycometabolism. The study suggested that the metabolomics approach could be used as a potential powerful tool to investigate the biochemical change in certain physiopathological conditions, such as depression, as an early diagnostic means.

Long-term treatment with peony glycosides reverses chronic unpredictable mild stress-induced depressive-like behavior via increasing expression of neurotrophins in rat brain

The root part of Paeonia lactiflora Pall., commonly known as peony, is a commonly used Chinese herb for the treatment of depression-like disorders. Previous studies in our laboratory have showed that total glycosides of peony (TGP) produced antidepressant-like action in various mouse models of behavioral despair. The present study aimed to investigate the mechanism(s) underlying the antidepressant-like action of TGP by measuring neurotrophins including brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in non-stressed and chronic unpredictable mild stress (CUMS)-treated rats. TGP (80 or 160 mg/kg/day) was administered by oral gavage to the animals for 5 weeks. The results showed that CUMS caused depression-like behavior in rats, as indicated by the significant decreases in sucrose consumption and locomotor activity (assessed by open-field test). In addition, it was found that BDNF contents in the hippocampus and frontal cortex were significantly decreased in CUMS-treated rats. CUMS treatment also significantly decreased the level of NGF in the frontal cortex of the animals. Daily intragastric administration of TGP (80 or 160 mg/kg/day) during the five weeks of CUMS significantly suppressed behavioral and biochemical changes induced by CUMS. Treating non-stressed animals with TGP (160 mg/kg) for 5 weeks also significantly increased BDNF contents in the hippocampus and frontal cortex, and NGF contents in the frontal cortex. The results suggest that the antidepressant-like action of TGP is mediated, at least in part, by increasing the expression of BDNF and NGF in selective brain tissues.