Effect of chronic unpredictable mild stress on brain–pancreas relative protein in rat brain and pancreas

Dynamic regulation of phosphorylation of NMDA receptor GluN2B subunit tyrosine residues mediates ketamine rapid antidepressant effects

The rapid antidepressant effects of ketamine depend on the N-methyl-D-aspartate (NMDA) receptor containing 2B subunit (NR2B), whose function is influenced by its phosphorylated regulation and distribution within and outside synapses. It remains unclear if ketamine's rapid onset of antidepressant effects relies on the dynamic phosphorylated regulation of NR2B within and outside synapses. Here, we show that ketamine rapidlyalleviated depression-like behaviors and normalized abnormal expression of pTyr1472NR2B and striatal-enriched protein tyrosine phosphatase (STEP) 61 within and outside synapses in the medial prefrontal cortex (mPFC) induced by chronic unpredictable stress (CUS) and conditional knockdown of STEP 61, a key phosphatase of NR2B, within 1 hour after administration Together, our results delineate the rapid initiation of ketamine's antidepressant effects results from the restoration of NR2B phosphorylation homeostasis within and outside synapses. The dynamic regulation of phosphorylation of NR2B provides a new perspective for developing new antidepressant strategies.

The effect of Vortioxetine on the NLRP3 pathway and microglial activity in the prefrontal cortex in an experimental model of depression

BACKGROUND

Increasing evidence suggests that early life stress (ELS) and neuroinflammation are associated with the pathophysiology of depression. The purpose of this study was to determine the effects of Vortioxetine (VOR), a novel antidepressant, on ELS-induced behavioral changes and neuroinflammation.

METHOD

Wistar Albino 4-week-old male rats were divided into four groups: control; chronic unpredictable stress (CUMS), VOR, CUMS + VOR. Neurobehavioral assessment was performed on the first, 21st, and 42nd days. RT-PCR was used to detect the expression of P2X7, NLRP3, IL1β, IL18 in the prefrontal cortex. To assess the microglial activities of the prefrontal cortex, immunohistochemically stained CD68, and leukocyte common antigen (LCA) preparations were scanned with Manual WSI software, Basler camera, and scored.

RESULT AND DISCUSSION

Exposure to CUMS was associated with depression and anxiety-like behaviors, and administration of VOR led to improvement in these behaviors. NLRP3, IL-1β, and IL-18 were shown to be upregulated in the prefrontal cortex of CUMS rats, while their high expression was inhibited by VOR treatment. CD68 and LCA expressions were significantly higher in the CUMS group compared to the other groups.

CONCLUSION

According to these results, it may be considered that NLRP3 inflammasome-associated neuroinflammatory response and microglial activation may play a role in the etiopathogenesis of ELS.

Gynura procumbens and selected metabolites: Amelioration of depressive-like behaviors in mice and risperidone-induced hyperprolactinemia in rats

Gynura procumbens (Lour.) Merr., utilized in traditional Chinese medicine, is known for its liver-protective, liver-soothing, and depression-alleviating properties. This research examines the antidepressant and anti-hyperprolactinemia potentials of an ethanol extract from G. procumbens stems (EEGS) and specific metabolites. To model depression and hyperprolactinemia, chronic unpredictable mild stress (CUMS) was induced in mice and risperidone was administered to rats, respectively. Treatments involved administering low (5 mg/kg), medium (25 mg/kg), and high (125 mg/kg) doses of EEGS and certain metabolites to both models. Behavioral assessments were conducted in the CUMS-induced mice, while the CA3 neuronal damage in mice and histopathological alterations in rat mammary glands were evaluated using Nissl and Hematoxylin & Eosin staining techniques, respectively. EEGS decreased immobility times in the forced swimming and tail suspension tests in mice, enhancing their exploration of the central zone. It elevated the serum levels of 5-hydroxytryptamine, norepinephrine, estradiol, luteinizing hormone (LH), and testosterone in mice. Moreover, EEGS restored the neuronal cell arrangement in the CA3 area, reduced interleukin-1beta mRNA production, and increased the expression of interleukin-10 and beta-catenin mRNA. In the context of risperidone-induced hyperprolactinemia, EEGS lowered blood prolactin levels, reduced the dimensions of rat nipples, and enhanced LH, progesterone, and dopamine levels, alongside mitigating mammary hyperplasia. Among the EEGS selected metabolites, the combined effect of chlorogenic acid and trans-p-coumaric acid was found to be more effective than the action of each compound in isolation. Collectively, the findings indicate that EEGS and its selected metabolites offer promising antidepressant benefits while counteracting hyperprolactinemia.

Solifenacin promotes remyelination in cuprizone mouse model by inhibiting the Wnt/β-catenin signaling pathway

Demyelinating diseases are a type of neurological disorder characterized by the damage to the myelin sheath in the central nervous system. Promoting the proliferation and differentiation of oligodendrocyte precursor cells (OPCs) is crucial for treatment. Non-selective muscarinic receptor (MR) antagonists have been shown to improve remyelination in rodent models, although the mechanisms are still unclear. In this study, we treated cuprizone (CPZ)-induced demyelination mouse model with different concentrations of Solifenacin (Sol), a selective M3 receptor antagonist, to determine the optimal concentration for promoting remyelination. Behavioral tests and Luxol fast blue (LFB) staining were used to observe the extent of remyelination, while immunofluorescence was used to measure the expression levels of myelin-related proteins, including myelin basic protein (MBP) and platelet-derived growth factor receptor alpha (PDGFR-α). Western blot analysis was employed to analyze the expression levels of molecules associated with the Wnt/β-catenin signaling pathway. The results showed that Sol treatment significantly promoted myelin regeneration and OPCs differentiation in CPZ-induced demyelination mouse model. Additionally, Sol treatment inhibited the Wnt/β-catenin signaling pathway and reversed the effects of CPZ on OPCs differentiation. In conclusion, Sol may promote the differentiation of OPCs by inhibiting the Wnt/β-catenin signaling pathway, making it a potential therapeutic option for central nervous system demyelinating diseases.

A quantitative proteomic study reveals oxidative stress and synapse-related proteins contributed to TDCIPP exposure induced neurotoxicity

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) has been consistently identified in various environmental media and biological specimens. Current understanding of the in vivo toxicities of TDCIPP is limited, especially for potential for neurotoxic and cognitive impairment effects. To better evaluate the potential adverse effect of the chemical on learning and memory, Sprague Dawley (SD) rats were administered TDCIPP via gavage at doses of 40, 120, and 360 mg/kg/day for a period of 90 days. Quantitative proteomic analysis, immunohistochemistry, and Western blotting were employed to assess alterations in proteins following exposure to TDCIPP. An open field test and the Morris Water Maze were used to assess anxiety and spatial learning memory capacity. Administration of TDCIPP induced anxiety and cognitive impairments in rats. Additionally, a noteworthy decrease in the number of neurons was observed in the hippocampal CA3 and dentate gyrus (DG) regions. Proteomic and bioinformatic analyses revealed dysregulation of numerous hippocampal proteins, particularly those associated with synapses (PKN1) or oxidative stress (GSTM4, NQO1, and BMAL1), which was further confirmed by Western blot analysis. In sum, the cognitive impairment of rats caused by TDCIPP exposure was associated with dysregulation of synaptic and oxidative stress-related proteins.

Investigation of non-invasive focused ultrasound efficacy on depressive-like behavior in hemiparkinsonian rats

Depression is a common non-motor symptom in Parkinson's disease (PD) that includes anhedonia and impacts quality of life but is not effectively treated with conventional antidepressants clinically. Vagus nerve stimulation improves treatment-resistant depression in the general population, but research about its antidepressant efficacy in PD is limited. Here, we administered peripheral non-invasive focused ultrasound to hemiparkinsonian ('PD') and non-parkinsonian (sham) rats to mimic vagus nerve stimulation and assessed its antidepressant-like efficacy. Following 6-hydroxydopamine (6-OHDA) lesion, akinesia-like immobility was assessed in the limb-use asymmetry test, and despair- and anhedonic-like behaviors were evaluated in the forced swim test and sucrose preference test, respectively. After, tyrosine hydroxylase immuno-staining was employed to visualize and quantify dopaminergic degeneration in the substantia nigra pars compacta, ventral tegmental area, and striatum. We found that PD rats exhibited akinesia-like immobility and > 90% reduction in tyrosine hydroxylase immuno-staining ipsilateral to the lesioned side. PD rats also demonstrated anhedonic-like behavior in the sucrose preference test compared to sham rats. No 6-OHDA lesion effect on immobility in the forced swim test limited conclusions about the efficacy of ultrasound on despair-like behavior. However, ultrasound improved anhedonic-like behavior in PD rats and this efficacy was sustained through the end of the 1-week recovery period. The greatest number of animals demonstrating increased sucrose preference was in the PD group receiving ultrasound. Our findings here are the first to posit that peripheral non-invasive focused ultrasound to the celiac plexus may improve anhedonia in PD with further investigation needed to reveal its potential for clinical applicability.

Study on the drunkenness of Chinese Baijiu with representative flavor based on behavioral characteristics

The essential role of drunkenness on the healthy development of Chinese Baijiu was studied in this research. This study revealed the effects of Baijiu on the behaviors of mice and evaluated the degree of drunkenness of soy sauce-, strong-, light-, and light and soy sauce-flavored Baijiu. The parameters obtained from the open field test were transformed into the behavioral drunkenness index by mathematical statistical analysis and the drunkenness-associated key compounds of Baijiu were analyzed. The results showed that strong- and light-flavored Baijiu presented higher levels of drunkenness and sobriety than soy sauce-flavored Baijiu. Interestingly, light and soy sauce-flavored Baijiu showed low drunkenness but a high sobriety degree. Specifically, the degree of drunkenness was positively correlated with fusel alcohol and aldehydes but negatively correlated with esters and acids. This study will enrich references for Baijiu behavior studies and lay a foundation for the research and development of healthy Baijiu.

Continuous Ingestion of Lacticaseibacillus rhamnosus JB-1 during Chronic Stress Ensures Neurometabolic and Behavioural Stability in Rats

The intestinal microbiome composition and dietary supplementation with psychobiotics can result in neurochemical alterations in the brain, which are possible due to the presence of the brain–gut–microbiome axis. In the present study, magnetic resonance spectroscopy (MRS) and behavioural testing were used to evaluate whether treatment with Lacticaseibacillus rhamnosus JB-1 (JB-1) bacteria alters brain metabolites’ levels and behaviour during continuous exposure to chronic stress. Twenty Wistar rats were subjected to eight weeks of a chronic unpredictable mild stress protocol. Simultaneously, half of them were fed with JB-1 bacteria, and the second half was given a daily placebo. Animals were examined at three-time points: before starting the stress protocol and after five and eight weeks of stress onset. In the elevated plus maze behavioural test the placebo group displayed increased anxiety expressed by almost complete avoidance of exploration, while the JB-1 dietary supplementation mitigated anxiety which resulted in a longer exploration time. Hippocampal MRS measurements demonstrated a significant decrease in glutamine + glutathione concentration in the placebo group compared to the JB-1 bacteria-supplemented group after five weeks of stress. With the progression of stress, the decrease of glutamate, glutathione, taurine, and macromolecular concentrations were observed in the placebo group as compared to baseline. The level of brain metabolites in the JB-1-supplemented rats were stable throughout the experiment, with only the taurine level decreasing between weeks five and eight of stress. These data indicated that the JB-1 bacteria diet might stabilize levels of stress-related neurometabolites in rat brain and could prevent the development of anxiety/depressive-like behaviour.

Baicalin Attenuates Continuous Activation of β-Catenin Induced by Lipopolysaccharide (LPS) and Depression Complicated by Infertility in Male Rats

Background

Baicalin (BA) is a potential candidate drug to inhibit depressive behavior. However, the mechanism of BA's role on depression complicated with male infertility (DCMI) is still unclear. This study aimed to investigate the role of BA in alleviating inflammatory factor-induced DCMI by regulating β-catenin.

Methods

Firstly, we performed sucrose preference test (SPT), open field test (OFT), tail suspension test (TST), and forced swim test (FST) in the chronic unpredictable mild stress (CUMS) + lipopolysaccharide (LPS) model rats to study the effect of BA on depressive behavior. The levels of neuropeptide Y (NPY), testosterone (T), and IL-1β, IL-6, TNF-α, IL-10, and IL-4 in the peripheral blood plasma of normal people, patients with depression, and patients with DCMI were measured. Then, the levels of IL-1β, IL-6, TNF-α, IL-10, IL-4, β-catenin in rat testis and peripheral blood and ANXA2, APP, SEMG1, and SEMG2 in seminal plasma proteins were examined. Moreover, the level of β-catenin in the testicular tissue was detected. LPS was used to treat Sertoli cells, and the level of β-catenin was detected. Finally, we evaluated the reproductive phenotype and sperm motility of rats.

Results

BA (especially 100 mg/kg) could notably ameliorate depression-like behavior induced by CUMS + LPS. The levels of IL-4, IL-10, T, and NPY in depression patients, DCMI patients, and CUMS + LPS model rats elevated, while the levels of IL-1β, IL-6, and TNF-α were reduced. However, BA alleviated the changes in these factors. Moreover, BA alleviated male rat depression induced by CUMS + LPS. LPS upregulated β-catenin (NP) but could not adjust β-catenin (TP) level in rat Sertoli cells. BA relieved the symptoms of DCMI by regulating β-catenin. Furthermore, BA ameliorated the reproductive ability of depressed rats.

Conclusion

BA modulated β-catenin in the relief of inflammatory factor-induced DCMI.

Development and Clinical Application of Positron Emission Tomography Imaging Agents for Monoamine Oxidase B

Monoamine oxidase B (MAO-B) is a high-density protein in the brain mainly found on outer mitochondrial membranes, primarily in astroglia, but additionally in serotonergic neurons and in the substantia nigra in the midbrain. It is an enzyme that participates in the oxidative metabolism of important monoamines including dopamine, norepinephrine, benzylamine, and phenylethylamine. Elevated MAO-B density may be associated with astrogliosis and inhibiting MAO-B may reduce astrogliosis. MAO-B density is elevated in postmortem sampling of pathology for many neuropsychiatric diseases including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and alcohol use disorder. Initial development of positron emission tomography (PET) imaging agents focused on analogs of [¹¹C]L-deprenyl, with the most commonly applied being the deuterium substituted [¹¹C]L-deprenyl-D2. This latter radiotracer was modeled with an irreversible trapping compartment reflecting its irreversible binding to MAO-B. Subsequently, [¹¹C]SL25.1188, a reversible binding MAO-B radioligand with outstanding properties including high specific binding and excellent reversibility was developed. [¹¹C]SL25.1188 PET was applied to discover a substantive elevation of MAO-B binding in the prefrontal cortex in major depressive disorder (MDD) with an effect size of more than 1.5. Longer duration of MDD was associated with greater MAO-B binding throughout most gray matter regions in the brain, suggesting progressive astrogliosis. Important applications of [¹¹C]L-deprenyl-D2 PET are detecting a 40% loss in radiotracer accumulation in cigarette smokers, and substantial occupancy of novel therapeutics like EVT301 and sembragiline. Given the number of diseases with elevations of MAO-B density and astrogliosis, and the advance of [¹¹C]SL25.1188, clinical applications of MAO-B imaging are still at an early stage.

Regulation of the kynurenine/serotonin pathway by berberine and the underlying effect in the hippocampus of the chronic unpredictable mild stress mice

BACKGROUND

Depression is a common mental disorder and is one of the main causes of disability. Berberine (BBR), the major constituent alkaloid originally from the famous Chinese herb Huanglian (Coptis chinensis), has been shown to exert antidepressant-like effects. This study was to investigate the hypothesis that BBR treats depressive-like behavior by shifting the balance of the kynurenine (KYN)/serotonin (5-HT) pathway toward the 5-HT pathway through downregulated indoleamine 2,3-dioxygenase 1 (IDO1), monoamine oxidase A (MAOA) and upregulated dopamine decarboxylase (DDC) in hippocampus.

METHOD

A chronic unpredictable mild stress (CUMS) mice model of depression was established via 21 days unpredictable stimulation. Then the mice were randomly assigned into six groups, namely control, model, fluoxetine [FLU, (10 mg/kg)], BBRL (25 mg/kg), BBRM (50 mg/kg), and BBRH (100 mg/kg) groups. Behavioral assessments were conducted to evaluate the antidepressant effects of BBR. The levels of 5-HT, KYN, tryptophan (TRP), and 5-hydroxyindoleacetic acid (5-HIAA) in hippocampus were estimated using high performance liquid chromatography (HPLC). The mRNA and protein levels of DDC, MAOA and IDO1 in hippocampus were detected by real-time quantitative polymerase chain reaction (qRT-PCR) and western blot (WB), respectively.

RESULT

The results showed that a successful CUMS mice model was established through 21 days of continuous unpredictable stimulation, as indicated by the significant decrease in locomotor activity and increase in immobility time, reduction in body weight and sucrose preference rate etc. Compared with the normal group, the concentrations of KYN/TRP had significantly increased (p^## <0.01) and 5-HT/5-HIAA had decreased (p^#<0.05) at day 21 in the control group, but then improved after drug treatment with FLU and BBR. Compared with the normal group, the mRNA of IDO1 and MAOA were significantly upregulated (p^#<0.05) in the control group, MAOA and IDO1 gene were downregulated by FLU and BBR treatment. Protein expressions of IDO1 and MAOA was significantly increased (p^#<0.05) and DDC downregulated (p^##<0.01). BBR treatment downregulated IDO1 and MAOA, upregulated DDC.

CONCLUSIONS

BBR reversed the abnormalities of the KYN/5-HT pathway in depressed mice and achieved an excellent antidepressant effect. Its direct impact may be observed as changes in biological indicators in mice hippocampus tissue.

Imaging of astrocytes in posttraumatic stress disorder: A PET study with the monoamine oxidase B radioligand [11C]SL25.1188

Posttraumatic stress disorder (PTSD) is a debilitating mental health condition that results from exposure to traumatic event(s). Decreased astrocyte-related proteins (e.g., glial fibrillary acidic protein, GFAP) and atrophic astrocytes in corticolimbic brain areas implicated in PTSD have been reported in experimental models suggesting that astrocyte pathology may be a feature of this disorder. We used positron emission tomography (PET) of the monoamine oxidase (MAO)-B probe [¹¹C]SL25.1188 to test the hypothesis that levels of MAO-B, an index of astrocyte levels is decreased in PTSD. MAO-B availability ([¹¹C]SL25.1188 distribution volume) was measured in 13 participants with PTSD (∼39 years, 6F) and 17 healthy controls (HC) (∼31 years, 9F). A magnetic resonance image was acquired to delineate 6 cortiolimbic brain regions. PTSD was associated with a trending reduction in [¹¹C]SL25.1188 availability across regions (8-17%; p = 0.067) implicating the ventral striatum (p uncorrected = 0.015) and medial prefrontal cortex (p uncorrected = 0.060). [¹¹C]SL25.1188 availability was ∼30% lower in corticolimbic regions in PTSD with co-morbid major depressive disorder (MDD) (n = 4) vs HC (p = 0.001) and vs PTSD without MDD (p = 0.005). Our preliminary results do not suggest astrogliosis (inferred from elevated availability) in PTSD, but rather point to a loss of astrocytes or an independent downregulation of MAO-B in PTSD with more severe negative affect. These exploratory findings, which are partly in line with preclinical literature and recent PET observations of decreased microglia marker, Translocator Protein, in PTSD, warrant replication in a larger PTSD cohort.

A comprehensive gene-centric pleiotropic association analysis for 14 psychiatric disorders with GWAS summary statistics

BACKGROUND

Recent genome-wide association studies (GWASs) have revealed the polygenic nature of psychiatric disorders and discovered a few of single-nucleotide polymorphisms (SNPs) associated with multiple psychiatric disorders. However, the extent and pattern of pleiotropy among distinct psychiatric disorders remain not completely clear.

METHODS

We analyzed 14 psychiatric disorders using summary statistics available from the largest GWASs by far. We first applied the cross-trait linkage disequilibrium score regression (LDSC) to estimate genetic correlation between disorders. Then, we performed a gene-based pleiotropy analysis by first aggregating a set of SNP-level associations into a single gene-level association signal using MAGMA. From a methodological perspective, we viewed the identification of pleiotropic associations across the entire genome as a high-dimensional problem of composite null hypothesis testing and utilized a novel method called PLACO for pleiotropy mapping. We ultimately implemented functional analysis for identified pleiotropic genes and used Mendelian randomization for detecting causal association between these disorders.

RESULTS

We confirmed extensive genetic correlation among psychiatric disorders, based on which these disorders can be grouped into three diverse categories. We detected a large number of pleiotropic genes including 5884 associations and 2424 unique genes and found that differentially expressed pleiotropic genes were significantly enriched in pancreas, liver, heart, and brain, and that the biological process of these genes was remarkably enriched in regulating neurodevelopment, neurogenesis, and neuron differentiation, offering substantial evidence supporting the validity of identified pleiotropic loci. We further demonstrated that among all the identified pleiotropic genes there were 342 unique ones linked with 6353 drugs with drug-gene interaction which can be classified into distinct types including inhibitor, agonist, blocker, antagonist, and modulator. We also revealed causal associations among psychiatric disorders, indicating that genetic overlap and causality commonly drove the observed co-existence of these disorders.

CONCLUSIONS

Our study is among the first large-scale effort to characterize gene-level pleiotropy among a greatly expanded set of psychiatric disorders and provides important insight into shared genetic etiology underlying these disorders. The findings would inform psychiatric nosology, identify potential neurobiological mechanisms predisposing to specific clinical presentations, and pave the way to effective drug targets for clinical treatment.

Identifying pleiotropic genes for complex phenotypes with summary statistics from a perspective of composite null hypothesis testing

Pleiotropy has important implication on genetic connection among complex phenotypes and facilitates our understanding of disease etiology. Genome-wide association studies provide an unprecedented opportunity to detect pleiotropic associations; however, efficient pleiotropy test methods are still lacking. We here consider pleiotropy identification from a methodological perspective of high-dimensional composite null hypothesis and propose a powerful gene-based method called MAIUP. MAIUP is constructed based on the traditional intersection-union test with two sets of independent P-values as input and follows a novel idea that was originally proposed under the high-dimensional mediation analysis framework. The key improvement of MAIUP is that it takes the composite null nature of pleiotropy test into account by fitting a three-component mixture null distribution, which can ultimately generate well-calibrated P-values for effective control of family-wise error rate and false discover rate. Another attractive advantage of MAIUP is its ability to effectively address the issue of overlapping subjects commonly encountered in association studies. Simulation studies demonstrate that compared with other methods, only MAIUP can maintain correct type I error control and has higher power across a wide range of scenarios. We apply MAIUP to detect shared associated genes among 14 psychiatric disorders with summary statistics and discover many new pleiotropic genes that are otherwise not identified if failing to account for the issue of composite null hypothesis testing. Functional and enrichment analyses offer additional evidence supporting the validity of these identified pleiotropic genes associated with psychiatric disorders. Overall, MAIUP represents an efficient method for pleiotropy identification.

Decreased expression of microRNA-17 in hippocampal tissues and blood from mice with depression up-regulates the expression of PAI-1 mRNA and protein

This study determined the expression of plasminogen activator inhibitor-1 (PAI-1) and microRNA (miR)-17 in a mouse depression model. Forty male mice were divided evenly into control and depression groups. A chronic unpredictable mild stress (CUMS) model was constructed. qRT-PCR was used to determine the expression of PAI-1 mRNA and miR-17. Western blotting and ELISA were used to determine expression of PAI-1 protein. Dual luciferase reporter assay was carried out to identify direct interaction between miR-17 and PAI-1 mRNA. The mice with depression had elevated PAI-1 mRNA and protein in hippocampal tissues and blood. Expression of miR-17 was decreased in hippocampal tissues and blood from mice with depression. miR-17 bound with the 3'-UTR of PAI-1 mRNA to regulate its expression. This study demonstrated that miR-17 expression in hippocampal tissues and blood from mice with depression was decreased while expression of PAI-1 mRNA and protein was up-regulated. miR-17 participated in depression in mice by regulating PAI-1.

Cerebral MAO Activity Is Not Altered by a Novel Herbal Antidepressant Treatment

Inhibition of monoamine oxidase (MAO)-A/B can ameliorate depressive- and anxiety-related symptoms via increase of monoamine extracellular levels. However, such inhibition can also instigate hypertensive response following exposure to dietary tyramine (i.e., "the cheese effect"). Novel herbal treatment (NHT) is an herbal formula that has been demonstrated to reduce depressive- and anxiety-like symptoms in pre-clinical studies. The aim of the current study was to examine whether the therapeutic potential of NHT is underlain by inhibition of MAO-A/B and whether NHT poses a risk for tyramine hyper-potentiation. Unpredictable chronic mild stress (UCMS)-exposed mice and naïve mice were treated for 3 weeks with NHT (30 mg/kg; i.p.), the selective serotonin reuptake inhibitor (SSRI) escitalopram (15 mg/kg; i.p.), or saline. Subsequently, MAO-A/B activities in the hypothalamus, striatum, and prefrontal cortex (PFC) were assessed. Exposure to UCMS led to significant increases in both MAO-A and MAO-B activities in the hypothalamus (p < 0.001) and in the PFC (p < 0.01 for MAO-A; p < 0.001 for MAO-B). Neither NHT nor escitalopram had any notable effects. Treatment with NHT was supported as safe in terms of risk for inducing a hypertensive response. The antidepressant- and anxiolytic-like effects of NHT are mediated via pathways other than MAO-A/B inhibition.

Monoamine Oxidase B Total Distribution Volume in the Prefrontal Cortex of Major Depressive Disorder: An [11C]SL25.1188 Positron Emission Tomography Study

IMPORTANCE

Monoamine oxidase B (MAO-B) is an important, high-density enzyme in the brain that generates oxidative stress by hydrogen peroxide production, alters mitochondrial function, and metabolizes nonserotonergic monoamines. Recent advances in positron emission tomography radioligand development for MAO-B in humans enable highly quantitative measurement of MAO-B distribution volume (MAO-B VT), an index of MAO-B density. To date, this is the first investigation of MAO-B in the brain of major depressive disorder that evaluates regions beyond the raphe and amygdala.

OBJECTIVE

To investigate whether MAO-B VT is elevated in the prefrontal cortex in major depressive episodes (MDEs) of major depressive disorder.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study was performed at a tertiary care psychiatric hospital from April 1, 2014, to August 30, 2018. Twenty patients with MDEs without current psychiatric comorbidities and 20 age-matched controls underwent carbon 11-labeled [11C]SL25.1188 positron emission tomography scanning to measure MAO-B VT. All participants were drug and medication free, nonsmoking, and otherwise healthy.

MAIN OUTCOMES AND MEASURES

The MAO-B VT in the prefrontal cortex (PFC). The second main outcome was to evaluate the association between MAO-B VT in the PFC and duration of major depressive disorder illness.

RESULTS

Twenty patients with MDEs (mean [SD] age, 34.2 [13.2] years; 11 women) and 20 healthy controls (mean [SD] age, 33.7 [13.1] years; 10 women) were recruited. Patients with MDEs had significantly greater MAO-B VT in the PFC (mean, 26%; analysis of variance, F1,38 = 19.6, P < .001). In individuals with MDEs, duration of illness covaried positively with MAO-B VT in the PFC (analysis of covariance, F1,18 = 15.2, P = .001), as well as most other cortex regions and the thalamus.

CONCLUSIONS AND RELEVANCE

Fifty percent (10 of 20) of patients with MDEs had MAO-B VT values in the PFC exceeding those of healthy controls. Greater MAO-B VT is an index of MAO-B overexpression, which may contribute to pathologies of mitochondrial dysfunction, elevated synthesis of neurotoxic products, and increased metabolism of nonserotonergic monoamines. Hence, this study identifies a common pathological marker associated with downstream consequences poorly targeted by the common selective serotonin reuptake inhibitor treatments. It is also recommended that the highly selective MAO-B inhibitor medications that are compatible for use with other antidepressants and have low risk for hypertensive crisis should be developed or repurposed as adjunctive treatment for MDEs.

Chronic unpredictable environmental stress impair biochemical and physiological homeostasis: Role in diabetes mellitus

AIMS

Chronic unpredictable environmental stress (CUES) may induce predisposition to diabetes mellitus. This study investigates the role of CUES on impaired homeostasis.

MATERIAL AND METHODS

Stressed group mice (n = 20) were exposed to CUES for 16 weeks. Weekly body weight, feed consumption, feed efficiency ratio, fasting blood glucose were monitored. Plasma HbA1c, plasma cortisol, plasma epinephrine and plasma insulin, serum lipids, antioxidants and carbohydrate metabolizing enzymes activity were assessed along with DNA damage and histopathological examination of liver, kidney, pancreas, spleen and skeletal muscles.

RESULTS AND CONCLUSION

s: Fasting blood glucose levels & HbA1c in the stressed were significantly higher compared to control (p < 0.001). Serum lipids were found insignificantly higher in stressed mice compared to control. Body weights of the stressed mice and feed efficiency ratio were found significant (p < 0.001). Plasma corticosterone, plasma epinephrine, HOMA-IR was found to be significantly higher in the stressed group (p < 0.001). Plasma insulin level was found to be significantly lower in the stressed group (p < 0.001). Significant changes were observed in antioxidants level, carbohydrate metabolizing enzymes activity, peripheral tissues and DNA integrity. CUES initiates pathogenesis of diabetes.

Involvement of Hepatic SHIP2 and PI3K/Akt Signalling in the Regulation of Plasma Insulin by Xiaoyaosan in Chronic Immobilization-Stressed Rats

Background: Long-term exposure to chronic stress is thought to be a factor closely correlated with the development of metabolic disorders, such as diabetes mellitus and metabolic syndrome. Xiaoyaosan, a Chinese herbal formula, has been described in many previous studies to exert anxiolytic-like or antidepressant effects in chronically stressed rats. However, few studies have observed the effects of Xiaoyaosan on the metabolic disorders induced by chronic stress. Objective: We sought to investigate the effective regulation of Xiaoyaosan on 21-day chronic immobility stress (CIS, which is 3 h of restraint immobilization every day)-induced behavioural performance and metabolic responses and to further explore whether the effects of Xiaoyaosan were related to SHIP2 expression in the liver. Methods: Sixty male Sprague Dawley rats were randomly divided into a control group, a CIS group, a Xiaoyaosan group and a rosiglitazone group. The latter three groups were subjected to 21 days of CIS to generate the stress model. After 21 days of CIS, the effects of Xiaoyaosan on body weight, food intake, and behaviour in the open field test, the sucrose preference test and the forced swimming test were observed following chronic stress. Plasma insulin, cholesterol (CHOL), triglyceride (TG), low-density lipoprotein (LDL-C) and high-density lipoprotein (HDL-C) concentrations and blood glucose were examined, and the protein and mRNA expression levels of SHIP2, p85 and Akt in the liver were measured using RT-qPCR and immunohistochemical staining. Results: Rats exposed to CIS exhibited depression-like behaviours, decreased levels of plasma insulin, CHOL, LDL-C, TG and HDL-C, and increased blood glucose. Increased SHIP2 expression and reduced Akt, p-Akt and p85 expression were also observed in the liver. Xiaoyaosan exerted antidepressant effects and effectively reversed the changes caused by CIS. Conclusions: These results suggest that Xiaoyaosan attenuates depression-like behaviours and ameliorates stress-induced abnormal levels of insulin, blood glucose, CHOL, LDL-C and HDL-C in the plasma of stressed rats, which may be associated with the regulation of SHIP2 expression to enhance PI3K/Akt signalling activity in the liver.

Ω-3 fatty acids-supplementary in gestation alleviates neuroinflammation and modulates neurochemistry in rats

Background

The mechanisms underlying the association between immune activation and postpartum depression remained elusive. Although Ω-3 fatty acids possess anti-inflammatory properties, there is limited evidence directly linking the modulating effects of Ω-3 fatty acids on neuroimmune and neurochemistry to the antidepressant actions.

Methods

A between-groups design was used to assess the effects of reproductive status (virgin or parous) and Ω-3 fatty acids content (control and supplementary). Serum inflammatory cytokine levels (IL-1a, IL-1β, IL-2, IL-6, IL-12, TNF-a, IFN-γ) were evaluated using the Bio-Plex Luminex System. Moreover, we also measured the protein levels of Purinergic type 2X7 receptor (P2X7R), NOD-like receptor pyrin domain containing 3 (NLRP3) and Nuclear factor-kappaB (NF-κB). Lastly, we assessed the function of various neurotransmitter systems to link the inflammatory response and neurotransmitter metabolism.

Results

Pro-inflammatory cyrokines, including IL-1a, IL-6, TNF-a and IFN-γ were markedly induced in the serum of parous rats, although no significantly depressive-like behavior was found. Meanwhile, NLRP3 and NF-κB were decreased in certain brain areas. Moreover, gestational stress significantly induced neurochemical disturbance, which is partly restored by Ω-3 fatty acids supplementation.

Conclusions

These findings strengthen the link between inflammation, neurochemistry and postpartum depression, and further provide novel insights into the antidepressant effect of Ω-3 fatty acids.

The Unpredictable Chronic Mild Stress Protocol for Inducing Anhedonia in Mice

Depression is a highly prevalent and debilitating condition, only partially addressed by current pharmacotherapies. The lack of response to treatment by many patients prompts the need to develop new therapeutic alternatives and to better understand the etiology of the disorder. Pre-clinical models with translational merits are rudimentary for this task. Here we present a protocol for the unpredictable chronic mild stress (UCMS) method in mice. In this protocol, adolescent mice are chronically exposed to interchanging unpredictable mild stressors. Resembling the pathogenesis of depression in humans, stress exposure during the sensitive period of mice adolescence instigates a depressive-like phenotype evident in adulthood. UCMS can be used for screenings of antidepressants on the variety of depressive-like behaviors and neuromolecular indices. Among the more prominent tests to assess depressive-like behavior in rodents is the sucrose preference test (SPT), which reflects anhedonia (core symptom of depression). The SPT will also be presented in this protocol. The ability of UCMS to induce anhedonia, instigate long-term behavioral deficits and enable reversal of these deficits via chronic (but not acute) treatment with antidepressants strengthens the protocol's validity compared to other animal protocols for inducing depressive-like behaviors.

Elevated monoamine oxidase A activity and protein levels in rodent brain during acute withdrawal after chronic intermittent ethanol vapor exposure

BACKGROUND

A key component of alcohol dependence (AD), a severe form of alcohol use disorder, is the negative emotional state during withdrawal. Monoamine oxidase A (MAO-A) is an important enzyme that metabolizes monoamines and creates oxidative stress. Elevations in MAO-A level, especially in the prefrontal and anterior cingulate cortex (PFC and ACC), are associated with low mood states, including the dysphoria of early alcohol withdrawal in humans. The aim of the present study was to determine whether chronic alcohol vapor exposure causes an upregulation of MAO-A activity or level in the PFC and ACC of rodents during acute withdrawal.

METHODS

Sprague-Dawley rats were exposed to ethanol vapor or control condition for 17 h per day for 8 weeks. MAO-A activity and protein levels were measured immediately after exposure, acute withdrawal (24 h), protracted withdrawal (4 day), and protracted abstinence (3 weeks) (n = 16/group; 8 alcohol exposed, 8 control).

RESULTS

Chronic ethanol vapor exposure significantly elevated MAO-A activity and protein levels in the PFC and ACC at 24-h withdrawal (multivariate analysis of variance (MANOVA), activity: F_2,13 = 3.82, p = .05, protein: F_2,13 = 5.13, p = .02). There were no significant changes in MAO-A level or activity at other timepoints.

CONCLUSIONS

The results of this study suggest a causal relationship between acute alcohol withdrawal and elevated MAO-A levels and activity, clarifying the observation of greater MAO-A binding in human alcohol withdrawal. This has important implications for developing methods of targeting MAO-A and/or sequelae of its dysregulation in alcohol dependence.

MicroRNA-27a participates in the pathological process of depression in rats by regulating VEGFA

The present study aimed to determine the expression of vascular endothelial growth factor A (VEGFA) and microRNA (miRNA/miR)-27a in hippocampal tissues, and serum from a depression model of rats. In addition, the present study aimed to understand the mechanism of regulation of miR-27a in depression. A total of 40 male rats were selected, and divided into the control and depression model groups. The rats in the model group were subjected to 14 types of stimulations to model depression. By determining the body weight, syrup consumption rate and open field test score, the extent of depression in the rats was evaluated. Quantitative-polymerase chain reaction was used to determine the expression of VEGFA mRNA and miR-27a in hippocampal tissues, and serum. ELISA was used to measure the content of VEGFA protein in serum, while western blotting was employed to determine the expression of VEGFA protein in hippocampal tissues. A dual luciferase assay was carried out to identify the interactions between VEGFA mRNA and miR-27a. The rats in the depression model group showed depression symptoms and the depression model was successfully constructed. Rats with depression had lower VEGFA mRNA and protein expression in the hippocampus, and peripheral blood compared with the control group. Rats in the depression model group had reduced levels of miR-27a in the hippocampus and peripheral blood, which may be associated with the levels of VEGFA. miR-27a was able to bind with the 3′-untranslated region of VEGFA mRNA to regulate its expression. The present study demonstrated that miR-27a expression in hippocampal tissues and blood from rats with depression is upregulated, while the expression of VEGFA mRNA and protein is downregulated. miR-27a may participate in the pathological process of depression in rats by regulating VEGFA.

The antidepressant-like effect of trans-astaxanthin involves the serotonergic system

The antidepressant-like effect of trans-astaxanthin, a compound present rich in algae, was evaluated through behavioral and neurochemical methods. Results showed that trans-astaxanthin treatment significantly decreased the immobility time in force swim test and tail suspension test, but did not influence locomotor activity. Trans-astaxanthin treatment did not effectively antagonize hypothermia and ptosis induced by reserpine. However, pre-treatment with para-chlorophenylalanine abolished the anti-immobility effect of trans-astaxanthin in force swim and tail suspension test. These results suggested that the mechanism of antidepressant-like effect of trans-astaxanthin may involve the serotonergic system, but not noradrenaline system. This hypothesis was confirmed by neurochemical assays which showed that trans-astaxanthin increased serotonin levels in the hippocampus, frontal cortex, striatum and hypothalamus. Furthermore, our data suggested that trans-astaxanthin decreased indoleamine 2, 3-dioxygenase activity in the hippocampus, frontal cortex and hypothalamus. Inhibition of indoleamine 2,3-dioxygenase activity subsequently decreased the kynurenine/tryptophan ratio and increased the serotonin/tryptophan ratio in these brain regions. Taken together, these findings indicate that the antidepressant-like effect of trans-astaxanthin involves the serotonergic system.

An Ω-3 fatty acid-deficient diet during gestation induces depressive-like behavior in rats: the role of the hypothalamo–pituitary–adrenal (HPA) system

Low intake of omega-3 (Ω-3) polyunsaturated fatty acids (PUFAs) especially docosahexaenoic acid (DHA) is associated with postpartum depression.

Chronic Unpredictable Mild Stress Causing Cardiac and Thoracic Spinal Cord Electrophysiological Abnormalities May Be Associated with Increased Cardiac Expression of Serotonin and Growth-Associated Protein-43 in Rats

BACKGROUND

The aim of this study was to investigate the potential mechanisms by which chronic unpredictable mild stress (CMS) might induce cardiovascular disease.

METHODS

Twenty male Sprague-Dawley rats (weighing 180-250 g) were divided into the CMS group (CMS for 3 weeks) and control group (n = 10/group). Sucrose solution consumption, sucrose solution preference rate, and the open field test (horizontal and vertical movements) were used to confirm the establishment of the CMS model. Heart rate was determined in Langendorff-perfused hearts, and field action potential duration (FAPD) was measured in cardiac atrial tissue, cardiac ventricular tissue, and thoracic spinal cord segments 1-5. The expressions of serotonin (5-HT) and growth-associated protein-43 (GAP-43) in cardiac ventricular tissue were analyzed using immunohistochemistry and immunofluorescence.

RESULTS

Compared with the control group, sucrose solution consumption, sucrose solution preference rate, horizontal movement, and vertical movement were significantly lower in the CMS group (P < 0.01). The CMS group exhibited significant decreases in atrial and ventricular FAPDs (P < 0.05), as well as significant increases in heart rates (P < 0.05) and T1-5 spinal cord FAPD (P < 0.01), as compared with the control group. The expressions of 5-HT and GAP-43 in cardiac ventricular tissue were significantly higher in the CMS group than in controls (P < 0.01).

CONCLUSIONS

CMS causes cardiac and T1-5 spinal cord electrophysiological abnormalities as well as increased cardiac expression of 5-HT and GAP-43, indicating that CMS could potentially increase the risk of cardiovascular disease.

Paeoniflorin, the Main Active Ingredient of Shuyu Capsule, Inhibits Cav1.2 and Regulates Calmodulin/Calmodulin-Dependent Protein Kinase II Signalling

The aim of this study was to explore the mechanism underlying the antidepression activity of paeoniflorin, the main active ingredient of paeony extract and Shuyu capsules, and determine its effect on the calmodulin/calmodulin-dependent protein kinase II (CaM/CaMKII) signalling pathway and on the possible target, the voltage-gated calcium channel (Ca_v). Rats at the nonacceptance stage were selected for premenstrual syndrome (PMS) depression modelling. Behavioural assays were used for model testing. Rats were given Shuyu capsules, paeony extract, and bupleurum. Western blot analysis was used to assess the expression levels of calcium voltage-gated channel subunit alpha 1 C (CACNA1C), brain-derived neurotrophic factor, and CaM/CaMKII signalling pathway proteins. Intracellular Ca²⁺ concentration in CHO cell line was measured using Fluo-4-AM and whole-cell patch clamps. The PMS depression model was successfully established and demonstrated that Shuyu can mitigate depressive behaviour in a rat PMS model. Paeony extract did not affect CACNA1C protein expression in rat hippocampi but did affect Ca_v1.2-mediated CaM/CaMKII signalling pathways. Paeoniflorin significantly inhibited KCl-induced increases in intracellular Ca²⁺ concentration and Ca_v1.2 current density. Further, it may function via the CaM/CaMKII pathway and its downstream signalling molecules by regulating Ca_v1.2, thus playing an important role in the treatment and alleviation of affective disorders.

Re-evaluation of the interrelationships among the behavioral tests in rats exposed to chronic unpredictable mild stress

The chronic unpredictable mild stress model of depression has been widely used as an experimental tool to investigate human psychopathology. Our objective was to provide an update on the validity and reliability of the chronic unpredictable mild stress model, by analyzing the interrelationships among the indexes using stepwise discriminant analysis and Pearson correlation coefficient to examine the possible combinations. We evaluated the depressive rats in both the presence and the absence of chronic unpredictable mild stress, using weight change, percentage of sucrose preference, coat state, splash test, open-field test, elevated plus-maze test, forced swimming test, and Morris water maze test. The results showed that 6-week-long chronic unpredictable mild stress produces significant depression and anxiety-like behavior. The combination of body weight change, percentage of sucrose preference, coat state score, open-field score, grooming latency of splash test, immobility time in force swimming test, and platform crossing in the Morris water maze test can effectively discriminate between normal and chronic unpredictable mild stress rats. Strong interrelationships were noted among these indexes in both open-field test and elevated plus-maze test. In conclusion, there might be certain criteria for the combination of behavioral endpoints, which is advantageous to more effectively and reliably assess the chronic unpredictable mild stress induced depression model.

Banxia-houpu decoction restores glucose intolerance in CUMS rats through improvement of insulin signaling and suppression of NLRP3 inflammasome activation in liver and brain

ETHNOPHARMACOLOGICAL RELEVANCE

Banxia-houpu decoction is a famous formula in traditional Chinese medicine (TCM) with the powerful anti-depressant activity.

AIM OF THE STUDY

This study aimed to investigate the effect of Banxia-houpu decoction on glucose intolerance associated with anhedonia in chronic unpredictable mild stress (CUMS) rats, then to explore its underlying pharmacological mechanisms.

MATERIALS AND METHODS

After 6-week CUMS procedure, male Wistar rats were given Banxia-houpu decoction (3.29 and 6.58g/kg, intragastrically) for 6 weeks. Sucrose solution consumption test was employed to evaluate the anhedonia behavior. Oral glucose tolerance test (OGTT) was used to determine glucose tolerance. Serum levels of corticosterone, corticotropin-releasing factor (CRF), insulin and interleukin-1 beta (IL-1β) were measured by commercial enzyme-linked immunosorbent assay kits, respectively. Furthermore, the key proteins for insulin signaling, as well as nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, were analyzed by Western blot in periphery liver and brain regions hypothalamus, hippocampus and prefrontal cortex, respectively.

RESULTS

Banxia-houpu decoction significantly increased sucrose solution consumption and decreased serum corticosterone and CRF levels in CUMS rats, further demonstrating its antidepressant activity. More importantly, Banxia-houpu decoction improved glucose tolerance in OGTT in this animal model. Furthermore, it protected against CUMS-induced insulin signaling impairment in the liver, as well as hypothalamus and prefrontal cortex in rats. Although without significant effect on serum IL-1β levels, Banxia-houpu decoction inhibited NLRP3 inflammasome activation in the liver, hypothalamus, hippocampus and prefrontal cortex of CUMS rats, respectively.

CONCLUSIONS

The present study demonstrates that Banxia-houpu decoction suppresses NLRP3 inflammasome activation and improves insulin signaling impairment in both periphery liver and brain regions in CUMS rats, possibly contributing to its anti-depressive effect with glucose tolerance improvement. These results may provide the evidence that Banxia-houpu decoction is a potential antidepressant with the advantage to reduce the risk of comorbid depression with type 2 diabetes mellitus.

Acupuncture for behavioral changes of experimental depressive disorder: a systematic review and meta-analysis

Acupuncture is considered to be a promising alternative therapy for depression. Nevertheless, up to now, it remains controversial on the effects exerted by acupuncture on behavioral changes in depression models. Consequently, it’s necessary to develop a systematic review and meta-analysis to assess the effect of acupuncture for model rats of depression. Ultimately, 90 studies involving 1861 models were identified. Behavioral indicators including the number of crossings (NC) and the number of rearings (NR) in open field test (OFT), the capacity of sucrose intake (CSI) and the rate of sucrose intake (RSI) in sucrose intake test (SIT), final weight (FW) and gain weight (GW) were employed as main outcomes in depression model rats. The pooled results showed that acupuncture had not less effect than western medicine on improving NC, NR, FW, GW, RSI (P > 0.05). However, the CSI improvement was poorer compared with west medicine (P < 0.05). In conclusion, acupuncture has not less effect on behavior changes than western medicine, including improving NC, NR, RSI, FW and GW in depression models.

Subchronic glucocorticoids, glutathione depletion and a postpartum model elevate monoamine oxidase a activity in the prefrontal cortex of rats

Recent human brain imaging studies implicate dysregulation of monoamine oxidase-A (MAO-A), in particular in the prefrontal cortex (PFC) and anterior cingulate cortex (ACC), in the development of major depressive disorder (MDD). This study investigates the influence of four alterations underlying important pathologies of MDD, namely, chronic elevation of glucocorticoid levels, glutathione depletion, changes in female gonadal sex hormones and serotonin concentration fluctuation, on MAO-A and MAO-B activities in rats. Young adult rats exposed chronically to the synthetic glucocorticoid dexamethasone at 0, 0.05, 0.5, and 2.0mg/kg/day (osmotic minipumps) for eight days showed significant dose-dependent increases in activities of MAO-A in PFC (+17%, p<0.001) and ACC (+9%, p<0.01) and MAO-B in PFC (+14%, p<0.001) and increased serotonin turnover in the PFC (+31%, p<0.01), not accounted for by dexamethasone-induced changes in serotonin levels, since neither serotonin depletion nor supplementation affected MAO-A activity. Sub-acute depletion of the major antioxidant glutathione by diethyl maleate (5mmol/kg, i.p.) for three days, which resulted in a 36% loss of glutathione in PFC (p=0.0005), modestly, but significantly, elevated activities of MAO-A in PFC and MAO-B in PFC, ACC and hippocampus (+6-9%, p<0.05). Changes in estrogen and progesterone representing pseudopregnancy were associated with significantly elevated MAO-A activity in the ACC day 4-7 postpartum (10-18%, p<0.05 to p<0.0001) but not the PFC or hippocampus. Hence, our study provides data in support of strategies targeting glucocorticoid and glutathione systems, as well as changes in female sex hormones for normalization of MAO-A activities and thus treatment of mood disorders.

Decreased expression of 5-HT1A in the circumvallate taste cells in an animal model of depression

OBJECTIVE

It has been reported that stress can cause anhedonia, a core symptom of depression, and also affect taste responses of the stressed subjects. Anhedonia refers to a reduction of the ability to experience pleasure, which can be detected by decreased response to palatable food in rats. The present study was conducted to examine if stress-induced anhedonia is accompanied by changes in gene expression for taste.

DESIGN

For anhedonia test, rats had free choices of cookies, a palatable food, and chow for 1h following 1h of daily restraint sessions. To examine the development of behavioral depression by restraint stress, ambulatory activity and forced swim tests were performed. Taste cells were harvested from the circumvallate papillae of rats on the 1st, 3rd and 7th day of stress exposure and subjected to the analysis of gene expression for taste.

RESULTS

One hour of daily stress exposure did not affect chow intake during the entire experimental period. However, from day 2 cookie intake was suppressed, suggesting the development of anhedonia. Ambulatory activity was significantly decreased, and immobility during forced swim test was increased, after the 7th day of stress exposure, but not before. 5-HT1A mRNA expression, but not T1R2, T1R3, T2R6, α-gustducin or PLCβ2 mRNA expression, appeared to be decreased after the 3rd day of stress exposure.

CONCLUSION

Reduced expression of 5-HT1A in the taste cells, possibly leading to a reduced processing of taste information for palatable food, may additively contribute to the development of anhedonia as a pre-symptomatic feature of depression in stressed subjects.

Shuyu Capsules Relieve Premenstrual Syndrome Depression by Reducing 5-HT3AR and 5-HT3BR Expression in the Rat Brain

The effects of the Shuyu capsule on 5-HT_3AR and 5-HT_3BR expression in a rat model of premenstrual syndrome (PMS) depression and on 5-HT_3AR and 5-HT_3BR expression and hippocampal neuron 5-HT₃ channel current were investigated, to elucidate its mechanism of action against PMS depression. PMS depression model rats were divided into depression and Shuyu- and fluoxetine-treated groups, which were compared to control rats for frontal lobe and hippocampal 5-HT_3AR and 5-HT_3BR expression and behavior. The depressed model rats displayed symptoms of depression, which were reduced in treated and normal control rats. Frontal lobe and hippocampal 5-HT_3AR and 5-HT_3BR levels were significantly higher in the model versus the control group and were significantly lower in the Shuyu group. As compared to control rats, the 5-HT₃R channel current in the model group was significantly higher; the 5-HT₃R channel current in hippocampal neurons treated with serum from Shuyu group rats was significantly lower than that in those treated with model group serum. Thus, PMS depression may be related to 5-HT_3AR and 5-HT_3BR expression and increased 5-HT₃ channel current. Shuyu capsules rectified abnormal 5-HT_3AR and 5-HT_3BR expression and 5-HT₃ channel current changes in a rat model; this finding may provide insight into treating PMS depression.

Piperine potentiates the effects of trans-resveratrol on stress-induced depressive-like behavior: involvement of monoaminergic system and cAMP-dependent pathway

Stress can act as a precipitation factor in the onset of emotional disorders, particularly depression. Trans-resveratrol is a polyphenolic compound enriched in polygonum cuspidatum and has been found to exert antidepressant-like effects in our previous studies. In present study, we assessed the effects of trans-resveratrol used in combination with piperine, commonly known as a bioavailability enhancer, on chronic unpredictable mild stress-induced depressive-like behaviors and relevant molecular targets. Trans-resveratrol used alone reduced the immobility time of rats in the forced swimming test, with the maximal effects of trans-resveratrol around 60 % inhibition at the highest dose tested, 40 mg/kg. However, when a subthreshold dose of piperine, 2.5 mg/kg was used in combination with trans-resveratrol, the minimum effective dose of trans-resveratrol in reducing the immobility time was reduced to 20 mg/kg. Further evidence from neurochemical (monoamines in the frontal cortex and the hippocampus), biochemical (monoamine oxidase, MAO activities) and molecular biological (cAMP, PKA, CREB and BDNF) assays supported the findings in the behavioral studies. These results suggest that the co-treatment strategy with trans-resveratrol and piperine might be an alternative therapy that provides efficacious protection against chronic stress.

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 RELEVANCE

Gastrodia 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 STUDY

To 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 METHODS

UCMS 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).

RESULTS

WGE 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.

CONCLUSION

The 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.

Depression mediates impaired glucose tolerance and cognitive dysfunction: A neuromodulatory role of rosiglitazone

Comorbidity of depression and diabetes is a serious risk factor worsening the complications such as cognitive function and locomotion. Treatment under this condition becomes extremely complicated. Insulin signaling and autophagy pathways are involved in modulation of learning and memory. Rosiglitazone (ROSI) ameliorate cognitive deficit associated with depression and insulin resistance. In the present study, we investigated the effect of ROSI against chronic unpredictable stress (CUS) induced depression as a risk factor for diabetes and behavioral dysfunctions. Adult male Swiss albino mice were exposed to CUS alongside ROSI (5mg/kg/day) treatment for 21days. Thereafter, animals were subjected to different behavioral studies to assess depressive like behavior, cognition and locomotion. The effect of ROSI on insulin signaling, autophagy and apoptosis were evaluated in the hippocampus. CUS resulted in depressive like behavior, cognitive impairment and hypolocomotion associated with oxidative stress, impaired glucose tolerance and hypercorticosteronemia. CUS significantly impaired hippocampal insulin signaling, membrane translocation of glucose transporter type 4 (GLUT4) as well as decreased the expression of autophagy5, autophagy7, B-cell lymphoma 2 and apoptosis inhibitory protein 2. ROSI significantly reduced depressive like behavior, postprandial blood glucose, hypercorticosteronemia, oxidative and inflammatory stress, and apoptosis in stressed mice. Moreover, ROSI treatment effectively improved hippocampal insulin signaling, GLUT4 membrane translocation and cognitive performance in depressed mice. ROSI administration might prove to be effective for neurological disorders associated with depressive like behavior and impaired glucose tolerance.

Effects of Electroacupuncture on Chronic Unpredictable Mild Stress Rats Depression-Like Behavior and Expression of p-ERK/ERK and p-P38/P38

We investigate the antidepressant-like effect and mechanism of electroacupuncture (EA) on a chronic unpredictable mild stress rats depression-like behavior. In our study, depression in rats was induced by unpredictable chronic mild stress (UCMS) and isolation for four weeks. Male Sprague-Dawley rats were randomly divided into four groups: Normal, Model, EA, and Sham EA. EA treatment was administered for two weeks, once a day for five days a week. Two acupoints, Yintang (EX-HN3) and Baihui (GV20), were selected. For sham EA, acupuncture needles were inserted shallowly into the acupoints: EX-HN3 and GV20. No electrostimulator was connected. The antidepressant-like effect of the electroacupuncture treatment was measured by sucrose intake test, open field test, and forced swimming test in rats. The protein levels of phosphorylated extracellular regulated protein kinases (p-ERK1/2)/ERK1/2 and p-P38/P38 in the hippocampus (HP) were examined by Western blot analysis. Our data demonstrate that EA treatment decreased the immobility time of forced swimming test and improved the sucrose solution intake in comparison to unpredictable chronic mild stress and placebo sham control. Electroacupuncture may act on depression by enhancing p-ERK1/2 and p-p38 in the hippocampus.

Orientin improves depression-like behavior and BDNF in chronic stressed mice

SCOPE

Oxidative stress is involved in chronic stress-induced depression and the disruption of neurotransmission and neuroplasticity. Recently, orientin, a phenolic compound abundant in some fruits, millet, and herbs, has been shown to have antioxidant properties. This study investigated the potential antidepressant effects of orientin against chronic stress and its underlying mechanisms.

METHODS AND RESULTS

The chronic unpredictable mild stress (CUMS) model was used to investigate the effects of orientin on behavior and biochemical alterations in mice. After 2 weeks of the CUMS protocol, the mice were treated with orientin (20 mg/kg and 40 mg/kg, oral gavage) for 3 weeks. Administration of orientin significantly alleviated the CUMS-induced depression-like behavior, including sucrose preference reduction, locomotor activity decline, and hypomotility. Orientin treatment attenuated the oxidative stress markers and increased the concentrations of serotonin and norepinephrine in the hippocampus and prefrontal cortex of CUMS mice. Orientin treatment also increased the brain-derived neurotrophic factor and synapse-associated proteins (synaptophysin and postsynaptic density protein 95) of CUMS mice.

CONCLUSION

Orientin exerts antidepressant-like effects on CUMS mice, specifically by improving central oxidative stress, neurotransmission, and neuroplasticity. Therefore, supplementation with orientin-enriched food or fruit could be beneficial as a preventive strategy for chronic stress-induced depression.

Dopamine Receptor D2 and Associated microRNAs Are Involved in Stress Susceptibility and Resistance to Escitalopram Treatment

BACKGROUND

Early life stress has been demonstrated to increase the risk of developing depression in adulthood. However, the roles and associated molecular mechanisms of stresses in the onset and relapse of depression have yet to be fully elucidated.

METHODS

Depression-like behaviors were induced in rats by maternal deprivation and chronic unpredictable stress. Depression- and anxiety-like behaviors of rats, dopamine receptor D2 level, and microRNAs expression in rats' brain tissues were measured.

RESULTS

Chronic unpredictable stress alone induced depression-like behaviors in rats, but maternal deprivation enhanced the effect of chronic unpredictable stress. Escitalopram significantly decreased depression-like behaviors in chronic unpredictable stress rats but was less effective in maternal deprivation with chronic unpredictable stress rats. Maternal deprivation increased dopamine receptor D2 messenger RNA expression and decreased microRNA-9 expression in the striatum. Chronic unpredictable stress increased dopamine receptor D2 mRNA and protein levels and decreased microRNA-9 expression in the nucleus accumbens. Furthermore, maternal deprivation enhanced the effect of chronic unpredictable stress on dopamine receptor D2 gene and microRNA-9 expression. Chronic unpredictable stress increased the expression of microRNA-326 in the nucleus accumbens but decreased it in the striatum, whereas maternal deprivation elevated microRNA-326 expression in the striatum. Escitalopram normalized microRNA-326 expression but had no effect on the expression of microRNA-9, dopamine receptor D2 mRNA, and dopamine receptor D2 protein in both the nucleus accumbens and striatum. The in vitro study showed that only microRNA-9 directly targeted the 3' untranslated region of dopamine receptor D2 mRNA and inhibited dopamine receptor D2 protein expression.

CONCLUSION

Early life stress enhanced the susceptibility to late life stress and resistance to escitalopram treatment through decreasing microRNA-9 expression and subsequently upregulating dopamine receptor D2 expression in the nucleus accumbens. microRNA-326 may be a novel target of escitalopram.

Reduced cholesterol is associated with the depressive-like behavior in rats through modulation of the brain 5-HT1A receptor

Background

Low serum cholesterol levels are related to an increased risk of depression and its serious consequences. However, the effect of central cholesterol on depressive disorder and its potential regulatory mechanism is poorly understood. Therefore, brain cholesterol in patients with depression may not only decrease the risk for developing this disease but also increase the beneficial effects of treatment for depression.

Methods

In current study, rats were exposed to chronic mild stress (CMS) for consecutive 28 days, and the depressive-like behavior was tested by sucrose preference test, immobility in the forced swim test, locomotor activity in the open field test, decreased bodyweight and food intake. Additionally, the total cholesterol levels in the medial prefrontal cortex (mPFC) and the hippocampus of rats were measured by gas chromatograph mass spectrometer. Finally, 5-HT1A receptor antagonist WAY100635 was used to determine the potential role of serotonin system in the interaction between central cholesterol and depression.

Results

CMS significantly reduced total cholesterol levels in the mPFC but not in the hippocampus and resulted in depressive-like behavior. Chronic supplementation of cholesterol by food reversed the depressive-like behavior induced by CMS. Furthermore, pre-injection of 5-HT1A receptor antagonist WAY100635 into the mPFC blocked the treatment effects of cholesterol on the reversal of behavioral response.

Conclusion

This finding suggested that cholesterol in the mPFC may have an impact on the sensitivity of the 5-HT1A receptor in the development and treatment of depression. The treatment benefits of cholesterol could be through modulation of the brain 5-HT1A receptor.

Danzhi Xiaoyao San ameliorates depressive-like behavior by shifting toward serotonin via the downregulation of hippocampal indoleamine 2,3-dioxygenase

ETHNOPHARMACOLOGICAL RELEVANCE

Danzhi Xiaoyao San (DXS) is a canonical Chinese medicine formula from Principles of Internal Medicine, which was written during the Ming dynasty. This formula is approved and commercialized for use in the prevention and treatment of affective disorders. This study is aimed to investigate the hypothesis that DXS treats depressive-like behavior by shifting the balance of the kynurenine (Kyn)/serotonin (5-HT) pathway toward the 5-HT pathway through the downregulation of hippocampal indoleamine 2,3-dioxygenase (IDO).

MATERIALS AND METHODS

Chemical fingerprints of gardenoside, paeoniflorin, ferulic acid, paeonol, and ligustilide in standard extraction were used as the material bases of DXS. Rats with depressive-like behavior induced by chronic unpredictable mild stress (CUMS) were randomly divided into four groups, namely the control, model, DXS, and fluoxetine groups. Cytokines, IDO, and tryptophan (Trp) catabolites were analyzed by enzyme-linked immunosorbent assay, western blot, and liquid chromatography-electrospray ionization tandem mass spectrometry, respectively.

RESULTS

DXS significantly increased crossing grid numbers, sucrose consumption, and body weight. This treatment significantly decreased the serum levels of tumor necrosis factor-α and interleukin 6 (IL-6). However, DXS elicited no significant effects on IL-1β, IL-2, and interferon γ. DXS downregulated the activity of IDO and subsequent production of Kyn in the hippocampus. This treatment upregulated the hippocampal contents of Trp and 5-HT but did not influence 5-HT turnover.

CONCLUSIONS

DXS exhibited antidepressant-like effects on rats exposed to CUMS. DXS reduced IDO activity to shift the balance of the Kyn/5-HT pathway toward the 5-HT pathway.

Anhedonia was associated with the dysregulation of hippocampal HTR4 and microRNA Let-7a in rats

OBJECTIVE

Depression is a serious mental illness. However, the molecular mechanisms responsible for the development of depression remain unknown.

METHODS

In this study, animal models of depression were established using maternal deprivation (MD) and chronic unpredictable stress (CUPS). Behavioral performance of rats was monitored by open field test, forced swim test, and sucrose consumption test. The expression of serotonin receptor-4 (Htr4) mRNA and Let-7a microRNA was detected by real-time PCR, while Htr4 protein level was measured by Western blot.

RESULTS

In the open field test, rats subjected to MD and CUPS exhibited significant decreases in vertical activity. CUPS rats spent less time in the central area and excreted more fecal pellets than MD and control rats. In the forced swim and sucrose consumption tests, CUPS and MD rats exhibited significantly longer floating time and consumed less sucrose than control rats. MD rats exhibited significantly shorter floating time and consumed less sucrose than CUPS rats. MD rats showed significantly lower Htr4 mRNA and protein expression and significantly higher Let-7a level in the hippocampus than control rats. Htr4 mRNA and protein expression negatively correlated with Let-7a expression. Htr4 mRNA expression positively correlated with sucrose preference rate, while Let-7a expression negatively correlated with the sucrose preference rate.

CONCLUSION

Anhedonia, not despair or a decline in exploratory interest, may be associated with upregulation of Let-7a and downregulation of Htr4 expression in the hippocampus. The hippocampal Htr4 level may be regulated by Let-7a in rats.