The mouse forced swim test

Food insecurity in older female mice affects food consumption, coping behaviors, and memory

Food insecurity correlates with poor physical and mental health in older individuals, but has not been studied in a laboratory animal model. This explorative study developed a laboratory mouse model for analyzing the impact of food insecurity on food consumption, stress coping mechanisms, exploratory behavior, and memory. 18-month-old CD-1 female mice were assigned to either the food insecurity exposure condition (31 mice, 8 cages) or the control condition (34 mice, 8 cages) by cage. Over four weeks, the mice that were exposed to food insecurity received varied, unpredictable portions of their baseline food consumption (50%, 75%, 125%, 150% of baseline) for four days, followed by ad libitum access for three days, to approximate the inconsistent access to food observed in households experiencing food insecurity. Behavioral tasks were conducted before and after food insecurity exposure. Mice in the food insecurity exposure condition ate less compared to control mice during food insecurity (two-way ANOVA: group x time interaction: F7,93 = 10.95, P < 0.01) but ate more when given access to high fat food (two-way ANOVA, group x time interaction: F1,14 = 11.14, P < 0.01). Mice exposed to food insecurity increased active escaping behaviors in the forced swim test (repeated measures two-way ANOVA, group x time interaction: F1,63 = 5.40, P = 0.023). Exploratory behaviors were unaffected by food insecurity. Mice exposed to food insecurity showed a reduction in memory (repeated measures two-way ANOVA, group x time interaction: F1,61 = 4.81, P = 0.037). These results suggest that exposure to food insecurity is associated with differences in food consumption patterns, active coping mechanisms, and memory. The behavioral changes associated with food insecurity may inform research on food insecurity's impact on health in elderly humans.

Differential effects by sex with Kmt5b loss

Lysine methyl transferase 5B (KMT5B) has been recently highlighted as a risk gene in genetic studies of neurodevelopmental disorders (NDDs), specifically, autism spectrum disorder (ASD) and intellectual disability (ID); yet, its role in the brain is not known. The goal of this work was to neurodevelopmentally characterize the effect(s) of KMT5B haploinsufficiency using a mouse model. A Kmt5b gene-trap mouse line was obtained from the Knockout Mouse Project. Wild type (WT) and heterozygous (HET) mice were subjected to a comprehensive neurodevelopmental test battery to assess reflexes, motor behavior, learning/memory, social behavior, repetitive movement, and common ASD comorbidities (obsessive compulsion, depression, and anxiety). Given the strong sex bias observed in the ASD patient population, we tested both a male and female cohort of animals and compared differences between genotypes and sexes. HET mice were significantly smaller than WT littermates starting at postnatal day 10 through young adulthood which was correlated with smaller brain size (i.e., microcephaly). This was more severe in males than females. HET male neonates also had delayed eye opening and significantly weaker reflexes than WT littermates. In young adults, significant differences between genotypes relative to anxiety, depression, fear, and extinction learning were observed. Interestingly, several sexually dimorphic differences were noted including increased repetitive grooming behavior in HET females and an increased latency to hot plate response in HET females versus a decreased latency in HET males. LAY SUMMARY: Lysine methyl transferase 5B (KMT5B) has been recently highlighted as a risk gene in neurodevelopmental disorders (NDDs), specifically, autism spectrum disorder (ASD) and intellectual disability (ID); yet its role in the brain is not known. Our study indicates that mice lacking one genomic copy of Kmt5b show deficits in neonatal reflexes, sociability, repetitive stress-induced grooming, changes in thermal pain sensing, decreased depression and anxiety, increased fear, slower extinction learning, and lower body weight, length, and brain size. Furthermore, several outcomes differed by sex, perhaps mirroring the sex bias in ASD.

Cardiac sensory afferents modulate susceptibility to anxio-depressive behaviour in a mouse model of chronic heart failure

AIM

Impairments in cerebral structure and cognitive performance in chronic heart failure (CHF) are critical components of its comorbidity spectrum. Autonomic afferents that arise from cardiac sensory fibres show enhanced activity with CHF. Desensitization of these fibres by local application of resiniferatoxin (RTX) during myocardial infarction (MI) is known to prevent cardiac hypertrophy, sympathetic hyperactivity and CHF. Whether these afferents mediate cerebral allostasis is unknown.

METHODS

CHF was induced by myocardial infarction. To evaluate if cardiac afferents contribute to cerebral allostasis, RTX was acutely applied to the pericardial space in controls (RTX) and in MI treated animals (MI/RTX). Subjects were then evaluated in a series of behavioural tests recapitulating different symptoms of depressive disorders. Proteomics of the frontal cortices (FC) was performed to identify contributing proteins and pathways responsible for behavioural allostasis.

RESULTS

Desensitization of cardiac afferents relieves hallmarks of an anxio/depressive-like state in mice. Unique protein signatures and regulatory pathways in FCs isolated from each treatment reveal the degree of complexity inherent in the FC response to stresses originating in the heart. While cortices from the combined treatment (MI/RTX) did not retain protein signatures from the individual treatment groups, all three groups suffer dysregulation in circadian entrainment.

CONCLUSION

CHF is comorbid with an anxio/depressive-like state and ablation of cardiac afferents relieves the despair phenotype. The strikingly different proteomic profiles observed in FCs suggest that MI and RTX lead to unique brain-signalling patterns and that the combined treatment, potentially through destructive interference mechanisms, most closely resembles controls.

Late gestational exposure to dexamethasone and fetal programming of abnormal behavior in Wistar Kyoto rats

INTRODUCTION

Fetal programming was characterized a few decades ago, explaining the correlation of physiological phenotypes of offspring exposed to early-life stress. High acute or chronic prenatal stress can overwhelm the enzymatic placental barrier, inducing transcriptional changes in the fetus that can result in different adverse behavioral and physiological phenotypes. The current study investigates the impact of exposure to the synthetic glucocorticoid, dexamethasone, during late gestation on behavioral outcomes.

METHODS

Pregnant Wistar Kyoto rats were given daily subcutaneous injections from gestational days 15-21 of either dexamethasone (0.9% NaCl, 4% EtOH, 100 µg kg^-1  day^-1 ) or were physically manipulated as naïve controls. Pups were raised normally until 17 weeks of age and underwent the Porsolt swim task and elevated plus maze for depressive and anxiety-like behaviors, respectively. Neural tissue was preserved for genetic analysis using quantitative real-time polymerase chain reaction.

RESULTS

Statistical analyses show significant disruption of behavior and genetic profiles of offspring exposed to dexamethasone in-utero. Exposed animals spent more time immobile on the swim task and entered open arms of the elevated plus maze more often than their naïve counterparts. In the prefrontal cortex, there was a sex by treatment interaction on gene expression relevant to neural transmission in ryanodine receptor 2, as well as increased gene expression in SNAP25, COMT, and LSAMP in males prenatally exposed to dexamethasone compared with controls. Both dysregulated genes and behavior are linked to decreased anxiety and fear inhibition.

CONCLUSION

Our results indicate adult offspring exposed to dexamethasone in-utero have a tendency toward passive stress-coping strategies and an inhibition of anxiety on behavioral tasks. Methyltransferase activity, synaptic activity, and cellular processes were disrupted in the prefrontal cortices of these animals. Specifically, genes involved in emotional response pathways were overexpressed, supporting the link between the behavioral and genetic profiles. Combined, we determine that dexamethasone offspring have adaptive predispositions when faced with novel situations, with increased immobility in the swim task and increased exploration on the elevated plus maze.

Gut microbiota determines the social behavior of mice and induces metabolic and inflammatory changes in their adipose tissue

The link between the gut microbiota and social behavior has been demonstrated, however the translational impact of a certain microbiota composition on stable behavioral patterns is yet to be elucidated. Here we employed an established social behavior mouse model of dominance (Dom) or submissiveness (Sub). A comprehensive 16S rRNA gene sequence analysis of Dom and Sub mice revealed a significantly different gut microbiota composition that clearly distinguishes between the two behavioral modes. Sub mice gut microbiota is significantly less diverse than that of Dom mice, and their taxa composition uniquely comprised the genera Mycoplasma and Anaeroplasma of the Tenericutes phylum, in addition to the Rikenellaceae and Clostridiaceae families. Conversely, the gut microbiota of Dom mice includes the genus Prevotella of the Bacteriodetes phylum, significantly less abundant in Sub mice. In addition, Sub mice show lower body weight from the age of 2 weeks and throughout their life span, accompanied with lower epididymis white adipose tissue (eWAT) mass and smaller adipocytes together with substantially elevated expression of inflammation and metabolic-related eWAT adipokines. Finally, fecal microbiota transplantation into germ-free mice show that Sub-transplanted mice acquired Sub microbiota and adopted their behavioral and physiological features, including depressive-like and anti-social behaviors alongside reduced eWAT mass, smaller adipocytes, and a Sub-like eWAT adipokine profile. Our findings demonstrate the critical role of the gut microbiome in determining dominance vs. submissiveness and suggest an association between gut microbiota, the eWAT metabolic and inflammatory profile, and the social behavior mode.

Saffron Extract-Induced Improvement of Depressive-Like Behavior in Mice Is Associated with Modulation of Monoaminergic Neurotransmission

Depressive disorders represent a major public health concern and display a continuously rising prevalence. Importantly, a large proportion of patients develops aversive side effects and/or does not respond properly to conventional antidepressants. These issues highlight the need to identify further therapeutic strategies, including nutritional approaches using natural plant extracts with known beneficial impacts on health. In that context, growing evidence suggests that saffron could be a particularly promising candidate. This preclinical study aimed therefore to test its antidepressant-like properties in mice and to decipher the underlying mechanisms by focusing on monoaminergic neurotransmission, due to its strong implication in mood disorders. For this purpose, the behavioral and neurobiochemical impact of a saffron extract, Safr’Inside™ (6.5 mg/kg per os) was measured in naïve mice. Saffron extract reduced depressive-like behavior in the forced swim test. This behavioral improvement was associated with neurobiological modifications, particularly changes in serotonergic and dopaminergic neurotransmission, suggesting that Safr’Inside™ may share common targets with conventional pharmacological antidepressants. This study provides useful information on the therapeutic relevance of nutritional interventions with saffron extracts to improve management of mood disorders.

A Role for the Amygdala in Impairments of Affective Behaviors Following Mild Traumatic Brain Injury

Mild traumatic brain injury (TBI) results in chronic affective disorders such as depression, anxiety, and fear that persist up to years following injury and significantly impair the quality of life for patients. Although a great deal of research has contributed to defining symptoms of mild TBI, there are no adequate drug therapies for brain-injured individuals. Preclinical studies have modeled these deficits in affective behaviors post-injury to understand the underlying mechanisms with a view to developing appropriate treatment strategies. These studies have also unveiled sex differences that contribute to the varying phenotypes associated with each behavior. Although clinical and preclinical studies have viewed these behavioral deficits as separate entities with unique neurobiological mechanisms, mechanistic similarities suggest that a novel approach is needed to advance research on drug therapy. This review will discuss the circuitry involved in the expression of deficits in affective behaviors following mild TBI in humans and animals and provide evidence that the manifestation of impairment in these behaviors stems from an amygdala-dependent emotional processing deficit. It will highlight mechanistic similarities between these different types of affective behaviors that can potentially advance mild TBI drug therapy by investigating treatments for the deficits in affective behaviors as one entity, requiring the same treatment.

Synaptic and behavioral effects of chronic stress are linked to dynamic and sex-specific changes in microglia function and astrocyte dystrophy

Emerging evidence indicates that males and females display different neurobiological responses to chronic stress which contribute to varied behavioral adaptations. In particular, pyramidal neurons undergo dendritic atrophy and synapse loss in the prefrontal cortex (PFC) of male, but not female, mice. Our recent work shows that chronic stress also provokes microglia-mediated neuronal remodeling, which contributes to synaptic deficits in the PFC and associated behavioral consequences in males. Separate studies indicate that chronic stress promotes astrocyte dystrophy in the PFC which is associated with behavioral despair. Notably, these prior reports focused primarily on stress effects in males. In the present studies, male and female mice were exposed to 14 or 28 days of chronic unpredictable stress (CUS) to assess molecular and cellular adaptations of microglia, astrocytes, and neurons in the medial PFC. Consistent with our recent work, male, but not female, mice displayed behavioral and cognitive deficits with corresponding perturbations of neuroimmune factors in the PFC after 14 days of CUS. Fluorescence-activated cell sorting and gene expression analyses revealed that CUS increased expression of select markers of phagocytosis in male PFC microglia. Confocal imaging in Thy1-GFP(M) mice showed that CUS reduced dendritic spine density, decreased GFAP immunolabeling, and increased microglia-mediated neuronal remodeling only in male mice. After 28 days of CUS, both male and female mice displayed behavioral and cognitive impairments. Interestingly, there were limited stress effects on neuroimmune factors and measures of microglial phagocytosis in the PFC of both sexes. Despite limited changes in neuroimmune function, reduced GFAP immunolabeling and dendritic spine deficits persisted in male mice. Further, GFAP immunolabeling and dendritic spine density remained unaltered in the PFC of females. These findings indicate that chronic stress causes sex-specific and temporally dynamic changes in microglial function which are associated with different neurobiological and behavioral adaptations. In all, these results suggest that microglia-mediated neuronal remodeling, astrocyte dystrophy, and synapse loss contribute to stress-induced PFC dysfunction and associated behavioral consequences in male mice.

Tetragonia tetragonioides Relieves Depressive-Like Behavior through the Restoration of Glial Loss in the Prefrontal Cortex

Tetragonia tetragonioides, which is a halophyte and grows widely in Asian-Pacific regions, has been used for the treatment of digestive disorders in traditional oriental medicine. This study examined the potential antidepressant effect of Tetragonia tetragonioides in an astroglial degeneration model of depression, which was established based on the postmortem study of depressive patients' brain presenting diminished astrocytes in the prefrontal cortex. C57BL/6 male mice were exposed to glial ablation in the prefrontal cortex by the administration of the gliotoxin, L-alpha-aminoadipic acid (L-AAA) to induce depression. Tetragonia tetragonioides at doses of 100 mg/kg and 300 mg/kg, imipramine at a dose of 15 mg/kg, and distilled water were orally administrated to mice for 18 days. Behavioral tests including the open field test (OFT), sucrose preference test (SPT), forced swimming test (FST), and tail suspension test (TST) were carried out after 2 days of L-AAA injection. The expression levels of GFAP and NeuN in the prefrontal cortex were determined by immunohistochemistry. Mice subjected to glial ablation in the prefrontal cortex displayed decreased sucrose consumption in SPT and increased immobility time in FST and TST. Treatment with imipramine and Tetragonia tetragonioides remarkably ameliorated the behavioral despair induced by L-AAA. In addition, immunohistochemistry analysis showed that treatment with Tetragonia tetragonioides significantly restored the glial loss as indicated by the elevated GFAP expression level. These findings suggest that Tetragonia tetragonioides exerts an antidepressant effect through the restoration of glial loss under conditions of depression and can be a candidate for an antidepressant agent.

GSNOR and ALDH2 alleviate traumatic spinal cord injury

Traumatic spinal cord injury (SCI) enhances the activity of S-nitrosoglutathione reductase (GSNOR) and inhibits the mitochondrial aldehyde dehydrogenase 2 (ALDH2) activity, resulting in prolonged and sustained pain and functional deficits. This study's objective was to test the hypotheses that GSNOR's specific inhibitor N6022 mitigates pain and improves functional recovery in a mouse model of SCI. Furthermore, the degree of recovery is enhanced and the rate of recovery is accelerated by an ALDH2 activator Alda-1. Using both wild-type and GSNOR^-/^- mice, the SCI model deployed for groups was contusion at the T9-T10 vertebral level. The enzymatic activity of GSNOR and ALDH2 was measured, and the expression of GSNOR and ALDH2 was determined by western blot analysis. Functional improvements in experimental animals were assessed with locomotor, sensorimotor, and pain-like behavior tests. Wild-type SCI animals had enhanced GSNOR activity and decreased ALDH2 activity, leading to neurovascular dysfunction, edema, and worsened functional outcomes, including locomotor deficits and pain. Compared to wild-type SCI mice, GSNOR^-/^- mice had better functional outcomes. Monotherapy with either GSNOR inhibition by N6022 or enhanced ALDH2 activity by Alda-1 correlated well with functional recovery and lessened pain. However, combination therapy provided synergistic pain-relieving effects and more significant functional recovery compared with monotherapy. Conclusively, dysregulations in GSNOR and ALDH2 are among the causative mechanisms of SCI injury. Either inhibiting GSNOR or activating ALDH2 ameliorates SCI. Combining the specific inhibitor of GSNOR (N6022) with the selective activator of ALDH2 (Alda-1) provides greater protection to the neurovascular unit and confers greater functional recovery. The study is novel, and the combination therapy (N6022 + Alda-1) possesses translational potential.

Phoneutria nigriventer Tx3-3 peptide toxin reduces fibromyalgia symptoms in mice

Fibromyalgia is characterized by the amplification of central nervous system pain with concomitant fatigue, sleep, mood disorders, depression, and anxiety. It needs extensive pharmacological therapy. In the present study, Swiss mice were treated with reserpine (0.25 mg/kg, s.c.) over three consecutive days, in order to reproduce the pathogenic process of fibromyalgia. On day 4, the administrations of the Tx3-3 toxin produced significant antinociception in the mechanical allodynia (87.16% ±12.7%) and thermal hyperalgesia (49.46% ± 10.6%) tests when compared with the PBS group. The effects produced by the classical analgesics (duloxetine 30 mg/kg, pramipexole 1 mg/kg, and pregabalin 30 mg/kg, p.o., respectively) in both of the tests also demonstrated antinociception. The administrations were able to increase the levels of the biogenic amines (5-HTP and DE) in the brain. The treatments with pramipexole and pregabalin, but not duloxetine, decreased the immobility time in the FM-induced animals that were submitted to the forced swimming test; however, the Tx3-3 toxin (87.45% ± 4.3%) showed better results. Taken together, the data has provided novel evidence of the ability of the Tx3-3 toxin to reduce painful and depressive symptoms, indicating that it may have significant potential in the treatment of FM.

Knockout of the circadian gene, Per2, disrupts corticosterone secretion and results in depressive-like behaviors and deficits in startle responses

Background

The Period Circadian Regulator 2 (Per2) gene is important for the modulation of circadian rhythms that influence biological processes. Circadian control of the hypothalamus-pituitary-adrenal (HPA) axis is critical for regulation of hormones involved in the stress response. Dysregulation of the HPA axis is associated with neuropsychiatric disorders. Therefore, it is important to understand how disruption of the circadian rhythm alters the HPA axis. One way to address this question is to delete a gene involved in regulating a central circadian gene such as Per2 in an animal model and to determine how this deletion may affect the HPA axis and behaviors that are altered when the HPA axis is dysregulated. To study this, corticosterone (CORT) levels were measured through the transition from light (inactive phase) to dark (active phase). Additionally, CORT levels as well as pituitary and adrenal mRNA expression were measured following a mild restraint stress. Mice were tested for depressive-like behaviors (forced swim test (FST)), acoustic startle response (ASR), and pre-pulse inhibition (PPI).

Results

The present results showed that Per2 knockout impacted CORT levels, mRNA expression, depressive-like behaviors, ASR and PPI. Unlike wild-type (WT) mice, Per2 knockout (Per2) mice showed no diurnal rise in CORT levels at the onset of the dark cycle. Per2−/− mice had enhanced CORT levels and adrenal melanocortin receptor 2 (Mc2R) mRNA expression following restraint. There were no changes in expression of any other pituitary or adrenal gene. In the FST, Per2−/− mice spent more time floating (less time struggling) than WT mice, suggesting increased depressive-like behaviors. Per2−/− mice had deficits in ASR and PPI startle responses compared to WT mice.

Conclusions

In summary, these findings showed that disruption of the circadian system via Per2 gene deletion dysregulated the HPA stress axis and is subsequently correlated with increased depressive-like behaviors and deficits in startle response.

The effectiveness of Bacopa monnieri (Linn.) Wettst. as a nootropic, neuroprotective, or antidepressant supplement: analysis of the available clinical data

Bacopa monnieri (Linn.) Wettst. has been used in traditional medicine as a drug to enhance and improve memory. In this regard, this study aims to provide B. monnieri's efficacy as a neuroprotective drug and as a nootropic against various neurological diseases. Literatures were collected, following Prisma guidelines, from databases, including Scopus, PubMed, Google Scholar, and Science Direct and were scrutinized using a quality scoring system. Means, standard deviations and 'n' numbers were extracted from the metrics and analyzed. Jamovi computer software for Mac was used to carry out the meta-analysis. The selected studies suggested that the plant extracts were able to show some improvements in healthy subjects which were determined in Auditory Verbal Learning Task, digit span-reverse test, inspection time task and working memory, even though it was not significant, as no two studies found statistically significant changes in the same two tests. B. monnieri was able to express modest improvements in subjects with memory loss, wherein only a few of the neuropsychological tests showed statistical significance. B. monnieri in a cocktail with other plant extracts were able to significantly reduce the effects of Alzheimer's disease, and depression which cannot be solely credited as the effect of B. monnieri. Although in one study B. monnieri was able to potentiate the beneficial effects of citalopram; on the whole, currently, there are only limited studies to establish the memory-enhancing and neuroprotective effects of B. monnieri. More studies have to be done in the future by comparing the effect with standard drugs, in order to establish these effects clinically in the plant and corroborate the preclinical data.

Selective inhibition of monoacylglycerol lipase is associated with passive coping behavior and attenuation of stress-induced dopamine release in the medial prefrontal cortex

The endocannabinoid system is involved in the regulation of the stress response, but the relative contribution of N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) and their mechanisms have to be elucidated. In this study, we compared the effects of the pharmacological inhibition of the two major endocannabinoid-degrading enzymes [fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) for AEA and 2-AG, respectively] on stress-coping [forced swim test (FST) and tail suspension test (TST)] and anxiety-like [elevated-plus maze (EPM) and light-dark test (LDT)] behaviors in wild-type and FAAH knockout mice. In vivo microdialysis estimated the effects of FAAH and MAGL inhibition on dopamine (DA) and serotonin (5-HT) levels in the medial prefrontal cortex (mPFC) during an FST. Mice were treated with PF-3845 (FAAH inhibitor), JZL184 (MAGL inhibitor), JZL195 (dual FAAH/MAGL inhibitor) or vehicle. Our data showed that PF-3845 increased latency to immobility and decreased total immobility time in FST, but no effects were observed in TST compared with vehicle-treated wild-type mice. By contrast, JZL184 decreased latency and increased immobility in TST and FST. JZL195 in wild-type mice and JZL184 in FAAH knockout mice reproduced the same passive coping behaviors as JZL184 in wild-type mice in TST and FST. In the microdialysis experiment, FST was associated with increased DA and 5-HT levels in the mPFC. However, JZL184-treated wild-type mice displayed a significant attenuation of forced swim stress-induced DA release compared with vehicle-treated wild-type mice and PF-3845-treated wild-type mice. Finally, FAAH and/or MAGL inhibitors induced robust and consistent anxiolytic-like effects in EPM and LDT. These results suggested differences between FAAH and MAGL inhibition in stress-coping behaviors. Notably, MAGL inhibition induced a consistent avoidant coping behavior and attenuated the stress-induced mPFC DA response in FST. However, more investigation is needed to elucidate the functional association between DA and 2-AG signaling pathways, and the molecular mechanism in the regulation of passive coping strategies during inescapable stress.

•

FAAH and/or MAGL inhibition induce opposite changes in stress-coping behaviors.

•

MAGL inhibition increases passive stress-coping behaviors in mice.

•

Passive stress-coping behaviors are regulated by 2-AG rather than AEA signaling.

•

MAGL inhibition attenuates mPFC dopamine increase in the forced swim test.

•

FAAH and/or MAGL inhibitors are associated with anxiolytic-like effects.

Changes in striatal dopamine transporters in bipolar disorder and valproate treatment

Background

Previous studies suggested that a disturbance of the dopamine system underlies the pathophysiology of bipolar disorder (BD). In addition, the therapeutic action of medications for treating BD, such as valproate (VPA), might modulate dopamine system activity, but it remains unclear. Here, we aimed to investigate the role of the striatal dopamine transporter (DAT) in BD patients and in social defeat (SD) mice treated with VPA.

Methods

We enrolled community-dwelling controls (N = 18) and BD patients (N = 23) who were treated with VPA in a euthymic stage. The striatal DAT availabilities were approached by TRODAT-1 single photon emission computed tomography. We also established a chronic SD mouse model and treated mice with 350 mg/kg VPA for 3 weeks. Behavioral tests were administered, and striatal DAT expression levels were determined.

Results

In humans, the level of striatal DAT availability was significantly higher in euthymic BD patients (1.52 ± 0.17 and 1.37 ± 0.23, p = 0.015). Moreover, the level of striatal DAT availability was also negatively correlated with the VPA concentration in BD patients (r = −0.653, p = 0.003). In SD mice, the expression of striatal DAT significantly increased (p < 0.001), and the SD effect on DAT expression was rescued by VPA treatment.

Conclusions

The striatal DAT might play a role in the pathophysiology of BD and in the therapeutic mechanism of VPA. The homeostasis of DAT might represent a new therapeutic strategy for BD patients.

A Comparison of Isolation Stress and Unpredictable Chronic Mild Stress for the Establishment of Mouse Models of Depressive Disorder

This study aimed to help to understand the influence of stress on depression, which reflects the social environments of especially solitary life and the increasing prevalence of depressive disorders. To determine the distinguishable features of two-representative animal models of stress-induced depressive disorder, we compared isolation stress (IS) and unpredictable chronic mild stress (UCMS). After 4-week of stress, both models showed significant depressive- and anxiety-like behaviors in an open field test (OFT; p < 0.01 for IS, p < 0.01 for UCMS), forced swimming test (FST; p < 0.01 for IS, p < 0.01 for UCMS), and tail suspension test (TST; p < 0.01 for IS, p < 0.05 for UCMS) along with alterations in serum corticosterone levels, serotonin activity in the dorsal raphe nuclei (DRN) and microglial activity in the dentate gyrus of the hippocampus (p < 0.05 for both parameters). In a comparison of the two stress models, IS strongly induced depressive and anxiety features, as indicated by all parameters: behavior test scores (p < 0.05 for OFT, FST, and TST), serum corticosterone levels (p < 0.05), immunohistological alterations for serotonin activity (p < 0.05) and microglial activity (p = 0.072). Our results indicate the suitability of IS for the development of animal models of depressive disorders and may reveal the medical impact of social isolation environment in modern society.

Effects of Withania somnifera (Ashwagandha) on Stress and the Stress- Related Neuropsychiatric Disorders Anxiety, Depression, and Insomnia

BACKGROUND

Withania somnifera (WS), also known as Ashwagandha, is commonly used in Ayurveda and other traditional medicine systems. WS has seen an increase in worldwide usage due to its reputation as an adaptogen. This popularity has elicited increased scientific study of its biological effects, including a potential application for neuropsychiatric and neurodegenerative disorders.

OBJECTIVE

This review aims to provide a comprehensive summary of preclinical and clinical studies examining the neuropsychiatric effects of WS, specifically its application in stress, anxiety, depression, and insomnia.

METHODS

Reports of human trials and animal studies of WS were collected primarily from the PubMed, Scopus, and Google Scholar databases.

RESULTS

WS root and leaf extracts exhibited noteworthy anti-stress and anti-anxiety activity in animal and human studies. WS also improved symptoms of depression and insomnia, though fewer studies investigated these applications. WS may alleviate these conditions predominantly through modulation of the hypothalamic-pituitary-adrenal and sympathetic-adrenal-medullary axes, as well as through GABAergic and serotonergic pathways. While some studies link specific withanolide components to its neuropsychiatric benefits, there is evidence for the presence of additional, as yet unidentified, active compounds in WS.

CONCLUSION

While benefits were seen in the reviewed studies, significant variability in the WS extracts examined prevents a consensus on the optimum WS preparation or dosage for treating neuropsychiatric conditions. WS generally appears safe for human use; however, it will be important to investigate potential herb-drug interactions involving WS if used alongside pharmaceutical interventions. Further elucidation of active compounds of WS is also needed.

Microbiota metabolites modulate the T helper 17 to regulatory T cell (Th17/Treg) imbalance promoting resilience to stress-induced anxiety- and depressive-like behaviors

Chronic stress disrupts immune homeostasis while gut microbiota-derived metabolites attenuate inflammation, thus promoting resilience to stress-induced immune and behavioral abnormalities. There are both peripheral and brain region-specific maladaptations of the immune response to chronic stress that produce interrelated mechanistic considerations required for the design of novel therapeutic strategies for prevention of stress-induced psychological impairment. This study shows that a combination of probiotics and polyphenol-rich prebiotics, a synbiotic, attenuates the chronic-stress induced inflammatory responses in the ileum and the prefrontal cortex promoting resilience to the consequent depressive- and anxiety-like behaviors in male mice. Pharmacokinetic studies revealed that this effect may be attributed to specific synbiotic-produced metabolites including 4-hydroxyphenylpropionic, 4-hydroxyphenylacetic acid and caffeic acid. Using a model of chronic unpredictable stress, behavioral abnormalities were associated to strong immune cell activation and recruitment in the ileum while inflammasome pathways were implicated in the prefrontal cortex and hippocampus. Chronic stress also upregulated the ratio of activated proinflammatory T helper 17 (Th17) to regulatory T cells (Treg) in the liver and ileum and it was predicted with ingenuity pathway analysis that the aryl hydrocarbon receptor (AHR) could be driving the synbiotic's effect on the ileum's inflammatory response to stress. Synbiotic treatment indiscriminately attenuated the stress-induced immune and behavioral aberrations in both the ileum and the brain while in a gut-immune co-culture model, the synbiotic-specific metabolites promoted anti-inflammatory activity through the AHR. Overall, this study characterizes a novel synbiotic treatment for chronic-stress induced behavioral impairments while defining a putative mechanism of gut-microbiota host interaction for modulating the peripheral and brain immune systems.

Shared neuroimmune and oxidative pathways underpinning Chagas disease and major depressive disorder

The cellular and molecular basis to understand the relationship between Chagas disease (CD), a infection caused by Trypanosoma cruzi, and depression, a common psychiatric comorbidity in CD patients, is largely unknown. Clinical studies show an association between CD and depression and preclinical evidence suggests that depressive-like behaviors in T. cruzi infected mice are due, at least partially, to immune dysregulation. However, mechanistic studies regarding this issue are still lacking. Herein, we present and discuss the state of art of data on CD and depression, and revise the mechanisms that may explain the development of depression in CD. We also discuss how the knowledge generated by current and future data may contribute to the discovery of new mechanisms underlying depressive symptoms associated with CD and, hence, to the identification of new therapeutic targets, which ultimately may change the way we see and treat CD and its psychiatric comorbidities.

Bufo viridis secretions improve anxiety and depression-like behavior following intracerebroventricular injection of amyloid β

Background and purpose:

Venenum Bufonis is a Chinese traditional medicine produced from the glandular secretions of toads that contain biogenic amines, which have anti-inflammatory properties. The present study aimed to examine the effect of Bufo viridis secretions (BVS) on anxiety and depression-like behavior and hippocampal senile plaques volume in an animal model of Alzheimer's disease (AD).

Experimental approach:

Thirty-eight male Wistar rats were used. AD was induced by amyloid-beta (Aβ_1-42) (10 μg/2 μL, intracerebroventricular injection, icv) and then BVS at 20, 40, and 80 mg/kg were injected intraperitoneally (ip) in six equal intervals over 21 days. Anxiety and depression-like behavior were assessed using behavioral tests including open field test (OFT), elevated plus maze (EPM), and forced swimming test (FST) 21 days after the surgery. The volume of senile plaques was assessed based on the Cavalieri principle.

Findings/Results:

Results of the OFT showed that the central crossing number and the time in the AD group were significantly decreased compared to the sham group (P < 0.01 and P < 0.001, respectively). Also, the values of these two parameters significantly increased in the AD + BVS80 group than the AD group (P < 0.05 and P < 0.001, respectively). The time spent in the closed arm in the EPM dramatically increased in the AD group compared to the sham group (P < 0.05) and significantly decreased in the AD + BVS80 group compared to the AD group (P < 0.05). Results of the FST indicated that immobility time had a reduction in the AD + BVS20 (P < 0.01), AD + BVS40, and AD + BVS80 groups compared to the AD group (P < 0.001). The volume of senile plaques in the hippocampus showed a reduction in the treatment groups in comparison with the AD group (P < 0.001 for all).

Conclusion and implications:

Results revealed that BVS injection could improve symptoms of anxiety and depression and decrease senile plaques in the hippocampus in an animal model of AD.

Selection and validation of optimal endogenous reference genes for analysis of quantitative PCR in four tissues pathologically associated with Kidney-yang deficiency syndrome following influenza A infection

Kidney-yang deficiency syndrome (KYDS) infected with the influenza virus is a suitable model to imitate a population at high-risk to influenza infection with a high rate of morbidity and mortality. However, the specific molecular mechanisms underlying this disease remain unclear. A stable reference gene is essential as an internal control for molecular biology research of this condition. Reverse-transcription-quantitative PCR (RT-qPCR) is considered an extremely sensitive technique used for absolute and relative quantification of target genes transcript levels. To accurately estimate the relative expression of genes in cells from mice with KYDS in response to infection with influenza A virus subtype H1N1 (A/H1N1) virus using RT-qPCR, it is necessary to identify suitable reference genes. In the present study, analysis of 10 reference genes (Act-β, β2m, GAPDH, Gusβ, Tubα, Grcc10, Eif4h, Rnf187, Nedd8 and Ywhae) was performed across a set of 4 tissue types: Lung; heart; liver; and kidney. KYDS mice were inoculated with A/H1N1 virus or a mock control. For analysis, geNorm, BestKeeper, NormFinder, and Bio-Rad Maestro^™ statistical programs were used for the estimation of the stability of the reference genes. The results were authenticated through extended experimental settings using a group of 10 samples, parallel to 3 additional innate immune system-associated genes of the host, TLR3, TLR7 and RIG-I, which were also analyzed using the same algorithms. From the 4 algorithms, taking into account the joint analyses of the ranking order outputs, the 2 genes Ywhae and Nedd8 were identified to be the most stable for mice with KYDS following infection with A/H1N1 virus. In contrast, the least stable genes in all 4 tissues were GAPDH and β2m. These results may affect the choice of reference genes in future studies that use RT-qPCR analysis of target genes in experimental conditions, such as mice with KYDS infected with influenza A virus.

Chronic but not acute pharmacological activation of SERCA induces behavioral and neurochemical effects in male and female mice

Intracellular calcium (Ca²⁺) homeostasis is a vital process to nerve cell survival and function with an intricate regulatory network. It is well established that the endoplasmic reticulum (ER) is a major intraneuronal Ca²⁺ storage and that the sarco/endoplasmic reticulum (SR/ER) calcium (Ca²⁺)-ATPase (SERCA) pump is a key regulator of cytosolic Ca²⁺ levels. SERCA pumps play a critical role in brain pathophysiology, thus SERCA comprises an emerging pharmacological target for the treatment of brain diseases. Interestingly, preclinical studies in rodents suggest that chronic pharmacological activation of SERCA2 by the quinoline derivative CDN1163 comprises a potential pharmacotherapeutic target in Alzheimer's and Parkinson's diseases. As little is known about the behavioral and neurochemical consequences of CDN1163 administration, in the current study we investigated the potential effects of acute (i.e., at 1 h) and chronic (i.e., 17 days) CDN1163 administration (i.e., 10 mg/kg and 20 mg/kg; intraperitoneally) on locomotor activity and relevant affective behaviors, as well as on monoaminergic neurotransmission in naïve C57BL/6J mice of both sexes. Interestingly, chronic, but not acute, CDN1163 administration induced anxiogenic and depressive-like behavioral effects in mice, as assessed in the open field (OF) test and the forced swim test (FST), respectively. In addition, chronic CDN1163 administration induced sustained sex- and brain region-dependent noradrenergic and serotonergic neurochemical effects ex vivo. Taken together, present findings support the critical role of SERCA-dependent Ca²⁺ handling in regulating behavior and neurochemical activity, and further highlight the need to consider sex in the development of SERCA-targeting pharmacotherapies for the treatment of debilitating brain disorders.

Colonization with the commensal fungus Candida albicans perturbs the gut-brain axis through dysregulation of endocannabinoid signaling

Anxiety disorders are the most prevalent mental health disorder worldwide, with a lifetime prevalence of 5-7 % of the human population. Although the etiology of anxiety disorders is incompletely understood, one aspect of host health that affects anxiety disorders is the gut-brain axis. Adolescence is a key developmental window in which stress and anxiety disorders are a major health concern. We used adolescent female mice in a gastrointestinal (GI) colonization model to demonstrate that the commensal fungus Candida albicans affects host health via the gut-brain axis. In mice, bacterial members of the gut microbiota can influence the host gut-brain axis, affecting anxiety-like behavior and the hypothalamus-pituitary-adrenal (HPA) axis which produces the stress hormone corticosterone (CORT). Here we showed that mice colonized with C. albicans demonstrated increased anxiety-like behavior and increased basal production of CORT as well as dysregulation of CORT production following acute stress. The HPA axis and anxiety-like behavior are negatively regulated by the endocannabinoid N-arachidonoylethanolamide (AEA). We demonstrated that C. albicans-colonized mice exhibited changes in the endocannabinoidome. Further, increasing AEA levels using the well-characterized fatty acid amide hydrolase (FAAH) inhibitor URB597 was sufficient to reverse both neuroendocrine phenotypes in C. albicans-colonized mice. Thus, a commensal fungus that is a common colonizer of humans had widespread effects on the physiology of its host. To our knowledge, this is the first report of microbial manipulation of the endocannabinoid (eCB) system that resulted in neuroendocrine changes contributing to anxiety-like behavior.

Hyper-Activation of mPFC Underlies Specific Traumatic Stress-Induced Sleep-Wake EEG Disturbances

Sleep disturbances have been recognized as a core symptom of post-traumatic stress disorders (PTSD). However, the neural basis of PTSD-related sleep disturbances remains unclear. It has been challenging to establish the causality link between a specific brain region and traumatic stress-induced sleep abnormalities. Here, we found that single prolonged stress (SPS) could induce acute changes in sleep/wake duration as well as short- and long-term electroencephalogram (EEG) alterations in the isogenic mouse model. Moreover, the medial prefrontal cortex (mPFC) showed persistent high number of c-fos expressing neurons, of which more than 95% are excitatory neurons, during and immediately after SPS. Chemogenetic inhibition of the prelimbic region of mPFC during SPS could specifically reverse the SPS-induced acute suppression of delta power (1–4 Hz EEG) of non-rapid-eye-movement sleep (NREMS) as well as most of long-term EEG abnormalities. These findings suggest a causality link between hyper-activation of mPFC neurons and traumatic stress-induced specific sleep–wake EEG disturbances.

Chronic postnatal chemogenetic activation of forebrain excitatory neurons evokes persistent changes in mood behavior

Early adversity is a risk factor for the development of adult psychopathology. Common across multiple rodent models of early adversity is increased signaling via forebrain Gq-coupled neurotransmitter receptors. We addressed whether enhanced Gq-mediated signaling in forebrain excitatory neurons during postnatal life can evoke persistent mood-related behavioral changes. Excitatory hM3Dq DREADD-mediated chemogenetic activation of forebrain excitatory neurons during postnatal life (P2–14), but not in juvenile or adult windows, increased anxiety-, despair-, and schizophrenia-like behavior in adulthood. This was accompanied by an enhanced metabolic rate of cortical and hippocampal glutamatergic and GABAergic neurons. Furthermore, we observed reduced activity and plasticity-associated marker expression, and perturbed excitatory/inhibitory currents in the hippocampus. These results indicate that Gq-signaling-mediated activation of forebrain excitatory neurons during the critical postnatal window is sufficient to program altered mood-related behavior, as well as functional changes in forebrain glutamate and GABA systems, recapitulating aspects of the consequences of early adversity.

Stress and adversity in early childhood can have long-lasting effects, predisposing people to mental illness and mood disorders in adult life. The weeks immediately before and after birth are critical for establishing key networks of neurons in the brain. Therefore, any disruption to these neural circuits during this time can be detrimental to emotional development. However, it is still unclear which cellular mechanisms cause these lasting changes in behavior.

Studies in animals suggest that these long-term effects could result from abnormalities in a few signaling pathways in the brain. For example, it has been proposed that overstimulating the cells that activate circuits in the forebrain – also known as excitatory neurons – may contribute to the behavioral changes that persist into adulthood.

To test this theory, Pati et al. used genetic engineering to modulate a signaling pathway in male mice, which is known to stimulate excitatory neurons in the forebrain. The experiments showed that prolonged activation of excitatory neurons in the first two weeks after birth resulted in anxious and despair-like behaviors as the animals aged. The mice also displayed discrepancies in how they responded to certain external sensory information, which is a hallmark of schizophrenia-like behavior. However, engineering the same changes in adolescent and adult mice had no effect on their mood-related behaviors.

This animal study reinforces just how critical the first few weeks of life are for optimal brain development. It provides an insight into a possible mechanism of how disruption during this time could alter emotional behavior. The findings are also relevant to psychiatrists interested in the underlying causes of mental illness after early childhood adversity.

Variation in the response to exercise stimulation in Drosophila: marathon runner versus sprinter genotypes

Animals' behaviors vary in response to their environment, both biotic and abiotic. These behavioral responses have significant impacts on animal survival and fitness, and thus, many behavioral responses are at least partially under genetic control. In Drosophila, for example, genes impacting aggression, courtship behavior, circadian rhythms and sleep have been identified. Animal activity also is influenced strongly by genetics. My lab previously has used the Drosophila melanogaster Genetics Reference Panel (DGRP) to investigate activity levels and identified over 100 genes linked to activity. Here, I re-examined these data to determine whether Drosophila strains differ in their response to rotational exercise stimulation, not simply in the amount of activity, but in activity patterns and timing of activity. Specifically, I asked whether there are fly strains exhibiting either a 'marathoner' pattern of activity, i.e. remaining active throughout the 2 h exercise period, or a 'sprinter' pattern, i.e. carrying out most of the activity early in the exercise period. The DGRP strains examined differ significantly in how much activity is carried out at the beginning of the exercise period, and this pattern is influenced by both sex and genotype. Interestingly, there was no clear link between the activity response pattern and lifespan of the animals. Using genome-wide association studies (GWAS), I identified 10 high confidence candidate genes that control the degree to which Drosophila exercise behaviors fit a marathoner or sprinter activity pattern. This finding suggests that, similar to other aspects of locomotor behavior, the timing of activity patterns in response to exercise stimulation is under genetic control.

Behavioral Deficits in Animal Models of Blast Traumatic Brain Injury

Blast exposure has been identified to be the most common cause for traumatic brain injury (TBI) in soldiers. Over the years, rodent models to mimic blast exposures and the behavioral outcomes observed in veterans have been developed extensively. However, blast tube design and varying experimental parameters lead to inconsistencies in the behavioral outcomes reported across research laboratories. This review aims to curate the behavioral outcomes reported in rodent models of blast TBI using shockwave tubes or open field detonations between the years 2008–2019 and highlight the important experimental parameters that affect behavioral outcome. Further, we discuss the role of various design parameters of the blast tube that can affect the nature of blast exposure experienced by the rodents. Finally, we assess the most common behavioral tests done to measure cognitive, motor, anxiety, auditory, and fear conditioning deficits in blast TBI (bTBI) and discuss the advantages and disadvantages of these tests.

Structural and biochemical imaging reveals systemic LPS-induced changes in the rat brain

Despite mounting evidence for the role of inflammation in Major Depressive Disorder (MDD), in vivo preclinical investigations of inflammation-induced negative affect using whole brain imaging modalities are scarce, precluding a valid model within which to evaluate pharmacological interventions. Here we used an E. coli lipopolysaccharide (LPS)-based model of inflammation-induced depressive signs in rats to explore brain changes using multimodal neuroimaging methods. During the acute phase of the LPS response (2 h post injection), prior to the emergence of a task-quantifiable depressive phenotype, striatal glutamine levels and splenial, retrosplenial, and peri-callosal hippocampal cortex volumes were greater than at baseline. LPS-induced depressive behaviors observed at 24 h, however, occurred concurrently with lower than control levels of striatal glutamine and a reversibility of volume expansion (i.e., shrinkage of splenial, retrosplenial, and peri-callosal hippocampal cortex to baseline volumes). In both striatum and hippocampus at 24 h, mRNA expression in LPS relative to control animals demonstrated alterations in enzymes and transporters regulating glutamine homeostasis. Collectively, the observed behavioral, in vivo structural and metabolic, and mRNA expression alterations suggest a critical role for astrocytic regulation of inflammation-induced depressive behaviors.

Antidepressant-like activity and safety profile evaluation of 1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione derivatives as 5-HT1A receptor partial agonists

Current antidepressant therapy has several disadvantages related to the properties of antidepressants. Considering their unfavourable features, the process of searching for new antidepressant drugs with better safety and tolerability requires consistent efforts and many complementary studies. Serotonin 5-HT_1A receptor is considered as an interesting target of antidepressant therapy. In the present study, the intrinsic activity at different signaling pathways coupled to serotonin 5-HT_1A receptor, antidepressant-like and pharmacokinetic properties, and the safety profile of two novel imidazopurine-2,4-dione derivatives, namely compounds AZ-853 (8-(4-(4-(2-fluorophenyl)piperazin-1-yl)butyl)-1,3-dimethyl-1H- imidazo[2,1-f]purine-2,4(3H,8H)-dione) and AZ-861 (1,3-dimethyl-8-(4-(4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)butyl)-1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione), were studied in animal models through in vitro and in vivo experiments. We demonstrated that AZ-853 and AZ-861, which structurally differ by one substituent and its placement in the phenyl ring, showed varied functional, pharmacological, and pharmacokinetic properties as well as side effect profiles. AZ-861 exhibited stronger agonistic action in all functional assays. After acute and repeated administration in mice, both compounds showed antidepressant-like activity in the forced swim test, which was partially mediated by 5-HT_1A receptor activation. AZ-853 showed a more potent antidepressant-like effect, presumably due to its better penetration into brain structures. Both compounds did not show anticholinergic properties, but after repeated administration, they induced weak sedation and lipid metabolism disturbances without affecting serum glucose level. The stronger α₁-adrenolytic effect of AZ-853 is responsible for decreased systolic blood pressure, and in contrast to AZ-861, AZ-853 induced weight gain in mice. The interesting comparative pharmacological profiles of AZ-853 and AZ-861 encourage to conduct further experiments to fully understand their mechanisms and differences in action.

Traumatic Stress Induces Prolonged Aggression Increase through Synaptic Potentiation in the Medial Amygdala Circuits

Traumatic stress can lead to heightened aggression which may be a symptom of psychiatric diseases such as PTSD and intermittent explosive disorder. The medial amygdala (MeA) is an evolutionarily conserved subnucleus of the amygdala that regulates attack behavior and behavioral responses to stressors. The precise contribution of the MeA in traumatic stress-induced aggression, however, requires further elucidation. In this study, we used foot shock to induce traumatic stress in mice and examine the mechanisms of prolonged aggression increase associated with it. Foot shock causes a prolonged increase in aggression that lasts at least one week. In vivo electrophysiological recordings revealed that foot shock induces potentiation of synapses formed between the MeA and the ventromedial hypothalamus (VmH) and bed nucleus of the stria terminalis (BNST). This synaptic potentiation lasts at least one week. Induction of synaptic depotentiation with low-frequency photostimulation (LFPS) immediately after foot shock suppresses the prolonged aggression increase without affecting non-aggressive social behavior, anxiety-like and depression-like behaviors, or fear learning. These results show that potentiation of the MeA-VmH and MeA-BNST circuits is essential for traumatic stress to cause a prolonged increase in aggression. These circuits may be potential targets for the development of therapeutic strategies to treat the aggression symptom associated with psychiatric diseases.

Potential Involvement of Adiponectin Signaling in Regulating Physical Exercise-Elicited Hippocampal Neurogenesis and Dendritic Morphology in Stressed Mice

Adiponectin, a cytokine secreted by mature adipocytes, proves to be neuroprotective. We have previously reported that running triggers adiponectin up-regulation which subsequently promotes generation of hippocampal neurons and thereby alleviates depression-like behaviors in non-stressed mice. However, under the stressing condition, whether adiponectin could still exert antidepressant-like effects following exercise remained unexplored. In this study, by means of repeated corticosterone injections to mimic stress insult and voluntary wheel running as physical exercise intervention, we examined whether exercise-elicited antidepressive effects might involve adiponectin's regulation on hippocampal neurogenesis and dendritic plasticity in stressed mice. Here we show that repeated injections of corticosterone inhibited hippocampal neurogenesis and impaired dendritic morphology of neurons in the dentate gyrus of both wild-type and adiponectin-knockout mice comparably, which subsequently evoked depression-like behaviors. Voluntary wheel running attenuated corticosterone-suppressed neurogenesis and enhanced dendritic plasticity in the hippocampus, ultimately reducing depression-like behaviors in wild-type, but not adiponectin-knockout mice. We further demonstrate that such proneurogenic effects were potentially achieved through activation of the AMP-dependent kinase (AMPK) pathway. Our study provides the first evidence that adiponectin signaling is essential for physical exercise-triggered effects on stress-elicited depression by retaining the normal proliferation of neural progenitors and dendritic morphology of neurons in the hippocampal dentate gyrus, which may depend on activation of the AMPK pathway.

Metformin Enhances Antidepressant/Antipsychotic Combination Therapy of Schizophrenia With Comorbid Depression in a Murine Model

Comorbid depressive disorders confound the diagnosis and therapy of schizophrenia. Using a murine model incorporating both MK801 and chronic unpredictable mild stress exposures, we successfully replicated both psychosis and depression. Ex vivo patch clamp recordings and in vivo calcium imaging demonstrated impaired neural activity in the prefrontal cortex (PFC). We then administered triple-drug combinations consisting of two antidepressants (mirtazapine and venlafaxine) plus an antipsychotic (either clozapine or olanzapine), and found improved PFC neuronal activity and performance in behavioral assays. Moreover, the addition of metformin to both psychotropic drug combinations brought further improvements in depressive and schizophrenic-like behaviors and physiological parameters. In summary, our data modeled the neuropathophysiology of schizophrenia with comorbid depression, and may inform drug intervention strategies.

Short-active photoperiod gestation induces psychiatry-relevant behavior in healthy mice but a resiliency to such effects are seen in mice with reduced dopamine transporter expression

A higher incidence of multiple psychiatric disorders occurs in people born in late winter/early spring. Reduced light exposure/activity level impacts adult rodent behavior and neural mechanisms, yet few studies have investigated such light exposure on gestating fetuses. A dysfunctional dopamine system is implicated in most psychiatric disorders, and genetic polymorphisms reducing expression of the dopamine transporter (DAT) are associated with some conditions. Furthermore, adult mice with reduced DAT expression (DAT-HT) were hypersensitive to short active (SA; 19:5 L:D) photoperiod exposure versus their wildtype (WT) littermates. Effects of SA photoperiod exposure during gestation in these mice have not been examined. We confirmed adult females exhibit a heightened corticosterone response when in SA photoperiod. We then tested DAT-HT mice and WT littermates in psychiatry-relevant behavioral tests after SA or normal active (NA; 12:12 L:D) photoperiod exposure during gestation and early life. SA-born WT mice exhibited sensorimotor gating deficits (males), increased reward preference, less immobility, open arm avoidance (females), less motivation to obtain a reward, and reversal learning deficits, vs. NA-born WT mice. DAT-HT mice were largely resilient to these effects, however. Future studies will determine the mechanism(s) by which SA photoperiod exposure influences brain development to predispose toward emergence of psychiatry-relevant behaviors.

Perinatal exposure to bisphenol A at the intersection of stress, anxiety, and depression

Endocrine-disrupting compounds (EDCs) are common contaminants in our environment that interfere with typical endocrine function. EDCs can act on steroid and nuclear receptors or alter hormone production. One particular EDC of critical concern is bisphenol A (BPA) due to its potential harm during the perinatal period of development. Previous studies suggest that perinatal exposure to BPA alters several neurotransmitter systems and disrupts behaviors associated with depression and anxiety in the rodent offspring later in life. Thus, dysregulation in neurotransmission may translate to behavioral phenotypes observed in mood and arousal. Many of the systems disrupted by BPA also overlap with the stress system, although little evidence exists on the effects of perinatal BPA exposure in relation to stress and behavior. The purpose of this review is to explore studies involved in perinatal BPA exposure and the stress response at neurochemical and behavioral endpoints. Although more research is needed, we suggest that perinatal BPA exposure is likely inducing variations in behavioral phenotypes that modulate their action through dysregulation of neurotransmitter systems sensitive to stress and endocrine disruption.

Neuroinflammatory and Behavioral Outcomes Measured in Adult Offspring of Mice Exposed Prenatally to E-Cigarette Aerosols

BACKGROUND

In an effort to decrease the rates of smoking conventional tobacco cigarettes, electronic cigarettes (e-cigarettes) have been proposed as an effective smoking cessation tool. However, little is known about their toxicological impacts. This is concerning given that e-cigarette use is perceived as less harmful than conventional tobacco cigarettes during pregnancy for both the mother and fetus.

OBJECTIVE

The goal of this study was to test the neurodevelopmental consequences of maternal e-cigarette use on adult offspring behavior and neuroimmune outcomes.

METHODS

Pregnant female CD-1 mice were randomly assigned to one of three treatment groups (n=8-10 per group) and exposed daily to either filtered air, propylene glycol and vegetable glycerol (50:50 PG/VG vehicle), or to PG/VG with 16mg/mL nicotine (+Nic). Whole-body exposures were carried out for 3 h/d, 7 d/week, from gestational day (GD)0.5 until GD17.5. Adult male and female offspring (8 weeks old) were assessed across a battery of behavioral assessments followed by region-specific quantification of brain cytokines using multiplex immunoassays.

RESULTS

Adult offspring of both sexes exposed to +Nic exhibited elevated locomotor activity in the elevated plus maze and altered stress-coping strategies in the forced swim task. Moreover, male and female offspring exposed to PG/VG with and without nicotine had a 5.2% lower object discrimination score in the novel object recognition task. In addition to differences in offspring behavior, maternal e-cigarette exposure with nicotine led to a reduction in interleukin (IL)-4 and interferon-gamma (IFNγ) in the diencephalon, as well as lower levels of hippocampal IFNγ (females only). E-cigarette exposure without nicotine resulted in a 2-fold increase of IL-6 in the cerebellum.

DISCUSSION

These findings support previous adverse findings of e-cigarette exposure on neurodevelopment in a mouse model and provide substantial evidence of persistent adverse behavioral and neuroimmunological consequences to adult offspring following maternal e-cigarette exposure during pregnancy. https://doi.org/10.1289/EHP6067.

Expression of Behavioral Phenotypes in Genetic and Environmental Mouse Models of Schizophrenia

Schizophrenia is a neuropsychiatric disorder characterized by multifactorial etiology involving complex interactions among genetic and environmental factors. "Multiple-hit" models of the disorder can explain its variable incidence and prevalence in related individuals. Hence, there is a dire need to understand these interactions in the emergence of schizophrenia. To test these factors in the emergence of schizophrenia-like behaviors, we employed a genetic mouse model of the disorder (harboring the DISC1 mutation) along with various environmental insults, such as early life stress (maternal separation of pups) and/or pharmacological interventions (ketamine injections). When assessed on a battery of behavioral tests, we found that environmental interventions affect the severity of behavioral phenotypes in terms of increased negative behavior, as shown by reduced mobility in the forced swim and tail suspension tests, and changes to positive and cognitive symptoms, such as increased locomotion and disrupted PPI along with reduced working memory, respectively. Among the various interventions, the genetic mutation had the most profound effect on behavioral aberrations, followed by an environmental intervention by ketamine injections and ketamine-injected animals that were maternally separated during early postnatal days. We conclude that although environmental factors increased the prevalence of aberrant behavioral phenotypes, genetic background is still the predominant influence on phenotypic alterations in these mouse models of schizophrenia.

Co-expression Network of mRNAs and lncRNAs Regulated by Stress-Linked Behavioral Assays

RATIONALE

Mood-related behavioral assays, designed typically on rodents' natural aversion to certain threats, are useful in studying the mechanisms of mood and in discovering effective treatments for neuropsychiatric disorders.

OBJECTIVES

Although reasonable attention has been paid to the conducted sequence, few studies address the argument whether a behavioral assay itself affects the intrinsic signaling, gene expression, and the subsequent performance of mice.

METHODS

We examined the short- (1 day) and long-term effects (7 and 14 days) of commonly used behavioral assays for anxiety and depression, including the elevated plus maze test (EPM), forced swimming test (FST), and tail suspension test (TST), on behaviors. We also investigated the effects of repeated behavioral assays on behaviors. The alterations in the expression profiles in the hippocampus experienced behavioral assays were explored via the integrative analysis of mRNA and lncRNA transcriptomes generated by RNA sequencing.

RESULTS

We found that one FST or TST can induce anxiety-related behaviors, while repeated FST or TST resulted in depression-related behaviors in mice. The altered behaviors were associated with extensive transcriptional alterations in the FST and TST hippocampus of mice. KEGG pathway analyses indicated that differentially expressed genes (DEGs) in the FST and TST hippocampus were enriched in anxiety- and metabolic-related pathways, respectively. Moreover, differentially expressed lncRNAs, showing correlations with DEGs, were linked to anxiety-related pathways in the FST hippocampus and metabolic-related pathways in the TST hippocampus.

CONCLUSIONS

Our study identified the unique and shared mRNAs and lncRNAs regulated by mood-related behavioral assays, emphasizing the importance of the sequence of and intervals between them.

Podoplanin Gene Disruption in Mice Promotes in vivo Neural Progenitor Cells Proliferation, Selectively Impairs Dentate Gyrus Synaptic Depression and Induces Anxiety-Like Behaviors

Podoplanin (Pdpn), a brain-tumor-related glycoprotein identified in humans and animals, is endogenously expressed in several organs critical for life support such as kidney, lung, heart and brain. In the brain, Pdpn has been identified in proliferative nestin-positive adult neural progenitor cells and in neurons of the neurogenic hippocampal dentate gyrus (DG), a structure associated to anxiety, critical for learning and memory functions and severely damaged in people with Alzheimer's Disease (AD). The in vivo role of Pdpn in adult neurogenesis and anxiety-like behavior remained however unexplored. Using mice with disrupted Pdpn gene as a model organism and applying combined behavioral, molecular biological and electrophysiological assays, we here show that the absence of Pdpn selectively impairs long-term synaptic depression in the neurogenic DG without affecting the CA3-Schaffer's collateral-CA1 synapses. Pdpn deletion also enhanced the proliferative capacity of DG neural progenitor cells and diminished survival of differentiated neuronal cells in vitro. In addition, mice with podoplanin gene disruption showed increased anxiety-like behaviors in experimentally validated behavioral tests as compared to wild type littermate controls. Together, these findings broaden our knowledge on the molecular mechanisms influencing hippocampal synaptic plasticity and neurogenesis in vivo and reveal Pdpn as a novel molecular target for future studies addressing general anxiety disorder and synaptic depression-related memory dysfunctions.

Recent Studies on Anti-Depressant Bioactive Substances in Selected Species from the Genera Hemerocallis and Gladiolus: A Systematic Review

Herbal therapy is a potential alternative applied to pharmacological alleviation of depression symptoms and treatment of this disorder, which is predicted by the World Health Organization (WHO) to be the most serious health problem worldwide over the next several years. It has been well documented that many herbs with psychotropic effects have far fewer side effects than a variety of pharmaceutical agents used by psychiatrists for the treatment of depression. This systematic review presents literature data on the antidepressant activity of representatives of the genera Hemerocallis (H. fulva and H. citrina Baroni, family Xanthorrhoeaceae) and Gladiolus (G. dalenii, family Iridaceae) and on biologically active compounds and their mechanisms of action to consider the application of herbal preparations supporting the treatment of depression.

Ovarian status dictates the neuroinflammatory and behavioral consequences of sub-chronic stress exposure in middle-aged female mice

Ovarian hormones influence the outcomes of stress exposure and are implicated in stress-related disorders including depression, yet their roles are often complex and seemingly contradictory. Importantly, depression and stress exposure are associated with immune dysregulation, and ovarian hormones have immunomodulatory properties. However, how ovarian hormones can influence the inflammatory outcomes of stress exposure is poorly understood. Here, we examined the effects of long-term ovariectomy on the behavioral and neuroinflammatory outcomes of sub-chronic stress exposure in middle-aged mice. Briefly, sham-operated and ovariectomized mice were assigned to non-stress groups or exposed to 6 days of variable stress. Mice were assessed on a battery of behavioral tests, and cytokine concentrations were quantified in the frontal cortex and hippocampus. In the frontal cortex, postsynaptic density protein-95 expression was examined as an index of excitatory synapse number and/or stability, and phosphorylated mitogen-activated protein kinases (MAPKs) were measured to explore potential cell signaling pathways elicited by stress exposure and/or ovarian hormones. Long-term ovariectomy modified the central cytokine profile by robustly reducing cytokine concentrations in the frontal cortex and modestly increasing concentrations in the hippocampus. Under non-stress conditions, long-term ovariectomy also reduced extracellular signal-regulated kinase (ERK) phosphoprotein expression in the frontal cortex and increased some measures of depressive-like behavior. The effects of sub-chronic stress exposure were however more pronounced in sham-operated mice. Notably, in sham-operated mice only, sub-chronic stress exposure increased IL-1β and IL-6:IL-10 ratio in the frontal cortex and hippocampus and reduced pERK1/2 expression in the frontal cortex. Further, although sub-chronic stress exposure increased anhedonia-like behavior regardless of ovarian status, it increased passive-coping behavior in sham-operated mice only. These data indicate that long-term ovariectomy has potent effects on the central cytokine milieu and dictates the neuroinflammatory and behavioral effects of sub-chronic stress exposure in middle-aged mice. These findings therefore suggest that the immunomodulatory properties of ovarian hormones are of relevance in the context of stress and possibly depression.

Chronic Stress Induces Activity, Synaptic, and Transcriptional Remodeling of the Lateral Habenula Associated with Deficits in Motivated Behaviors

Chronic stress (CS) is a major risk factor for the development of depression. Here, we demonstrate that CS-induced hyperactivity in ventral tegmental area (VTA)-projecting lateral habenula (LHb) neurons is associated with increased passive coping (PC), but not anxiety or anhedonia. LHb→VTA neurons in mice with increased PC show increased burst and tonic firing as well as synaptic adaptations in excitatory inputs from the entopeduncular nucleus (EP). In vivo manipulations of EP→LHb or LHb→VTA neurons selectively alter PC and effort-related motivation. Conversely, dorsal raphe (DR)-projecting LHb neurons do not show CS-induced hyperactivity and are targeted indirectly by the EP. Using single-cell transcriptomics, we reveal a set of genes that can collectively serve as biomarkers to identify mice with increased PC and differentiate LHb→VTA from LHb→DR neurons. Together, we provide a set of biological markers at the level of genes, synapses, cells, and circuits that define a distinctive CS-induced behavioral phenotype.

Spatiotemporal Role of Transforming Growth Factor Beta 2 in Developing and Mature Mouse Hindbrain Serotonergic Neurons

Transforming growth factor betas are integral molecular components of the signalling cascades defining development and survival of several neuronal groups. Among TGF-β ligands, TGF-β2 has been considered as relatively more important during development. We have generated a conditional knockout mouse of the Tgf-β2 gene with knock-in of an EGFP reporter and subsequently a mouse line with cell-type specific deletion of TGF-β2 ligand from Krox20 expressing cells (i.e., in cells from rhombomeres r3 and r5). We performed a phenotypic analysis of the hindbrain serotonergic system during development and in adulthood, determined the neurochemical profile in hindbrain and forebrain, and assessed behavioural performance of wild type and mutant mice. Mutant mice revealed significantly decreased number of caudal 5-HT neurons at embryonic day (E) 14, and impaired development of caudal dorsal raphe, median raphe, raphe magnus, and raphe obscurus neurons at E18, a phenotype that was largely restored and even overshot in dorsal raphe of mutant adult mice. Serotonin levels were decreased in hindbrain but significantly increased in cortex of adult mutant mice, though without any behavioural consequences. These results highlight differential and temporal dependency of developing and adult neurons on TGF-β2. The results also indicate TGF-β2 being directly or indirectly potent to modulate neurotransmitter synthesis and metabolism. The novel floxed TGF-β2 mouse model is a suitable tool for analysing the in vivo functions of TGF-β2 during development and in adulthood in many organs.

Glucocorticoid receptor antagonism prevents microglia-mediated neuronal remodeling and behavioral despair following chronic unpredictable stress

Synaptic deficits and neuronal dystrophy in the prefrontal cortex (PFC) are linked to behavioral and cognitive symptoms in depressed individuals. Preclinical studies indicate that chronic stress causes synaptic deficits on pyramidal neurons in the PFC that contribute to behavioral and cognitive impairments. Our recent work shows that chronic stress provokes microglia-mediated neuronal remodeling via neuronal colony stimulating factor (CSF)-1 signaling, leading to synaptic deficits and depressive-like behaviors. Other reports indicate that elevated corticosterone causes pyramidal neuron atrophy and microglia activation in the medial PFC, implicating glucocorticoid signaling in microglia-mediated neuronal remodeling following chronic stress. In this study, male mice were exposed to chronic unpredictable stress (CUS) and received daily administration of glucocorticoid receptor antagonist RU486 (25 mg/kg, i.p.). As expected, CUS exposure caused adrenal hypertrophy and elevated plasma corticosterone levels. Glucocorticoid receptor blockade prevented behavioral despair and cognitive impairments following CUS. Moreover, RU486 administration diminished CUS-induced CSF1 signaling in the PFC and reduced markers of phagocytosis on purified microglia. Confocal imaging in Thy1-GFP(M) mice showed that CUS increased microglia-mediated neuronal remodeling, and RU486 administration attenuated microglial engulfment of neuronal elements and prevented dendritic spine density deficits on pyramidal neurons following CUS. These results demonstrate that chronic stress-induced glucocorticoid signaling promotes CSF1 signaling and microglia-mediated neuronal remodeling in the medial PFC, which contributes to development of behavioral despair and cognitive impairments. This study presents primary evidence that neuroendocrine responses engage neuron-microglia interactions in the PFC; further implicating microglia in stress-induced neuronal remodeling, PFC dysfunction, and associated behavioral consequences.

Conclusions from a behavioral aging study on male and female F2 hybrid mice on age-related behavior, buoyancy in water-based tests, and an ethical method to assess lifespan

Due to strain-specific behavioral idiosyncrasies, inbred mouse strains are suboptimal research models for behavioral aging studies. The aim of this study is to determine age-related behavioral changes of F2 hybrid C57BL/6NxBALB/c male and female mice. Lifespan was followed (n_males=48, n_females=51) and cohorts of mature adult (7 months), middle-aged (15 months), and old mice (22 months of age; n=7-12 per group) were assessed regarding open-field activity, exploration, passive avoidance learning/memory, and depressive-like behavior. We found that both males and females demonstrated decreased exploratory behavior with age, while memory and depressive-like behavior were maintained. Females exhibited enhanced depressive-like behavior compared to males; however, a correlation between fat mass and swimming activity in the test directly accounted for 30-46% of this behavioral sex difference. In addition, we suggest a method to qualitatively estimate natural lifespan from survival analyses in which animals with signs of pain or severe disease are euthanized. This is, to our knowledge, the first behavioral study to consider both sex and aging in hybrid mice. We here define decreased exploratory behavior as a conserved hallmark of aging independent of sex, highlight the effect of buoyancy in water tests, and provide a method to assay lifespan with reduced animal suffering.

The animal cachexia score (ACASCO)

BACKGROUND

None of the published studies involving cancer cachexia experimental models have included a measure of the severity of the syndrome like the scoring system previously developed for human subjects. The aim of the present investigation was to define and validate a cachexia score usable in both rat and mouse tumor models.

METHODS

In order to achieve this goal, we included in the study one rat model (Yoshida AH-130ascites hepatoma) and two mouse models (Lewis lung carcinoma and Colon26 carcinoma). The Animal cachexia score (ACASCO) includes five components: (a) body and muscle weight loss, (b) inflammation and metabolic disturbances, (c) physical performance, (d) anorexia, and (e) quality of life measured using discomfort symptoms and behavioral tests.

RESULTS

Using the ACASCO values, three cut-off values were estimated by applying hierarchical cluster analysis. Four groups were originally described, one exactly below the observed mean, a second exactly over the mean, and two other groups adjusted to every cue (inferior and superior). The three cut-off values were estimated through maximization of the classification function. This was accomplished by using a similarity matrix based on the metric properties of the variables and assuming multinormal distribution. The results show that the four groups were: no cachexia, mild cachexia, moderate cachexia and advanced cachexia.

CONCLUSIONS

The results obtained allow us to conclude that the score could be very useful as an endpoint in pre-clinical studies involving therapeutic strategies for cancer cachexia. The potential usefulness of ACASCO relates to the primary endpoint in pre-clinical cancer cachexia drug evaluations.

Influence of intranasal exposure of MPTP in multiple doses on liver functions and transition from non-motor to motor symptoms in a rat PD model

Besides the effects on the striatum, the impairment of visceral organs including liver functions has been reported in Parkinson's disease (PD) patients. However, it is yet unclear if liver functions are affected in the early stage of the disease before the motor phase has appeared. The aim of our present study was thus to assess the effect of intranasal administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in different doses on striatum and liver functions. Deterioration of non-motor activities appeared on single exposure to MPTP along with rise in striatum oxidative stress and decline in antioxidant levels. Decreases in dopamine, noradrenaline, and GABA and increase in serotonin were detected in striatum. Motor coordination was impaired with a single dose of MPTP, and with repeated MPTP exposure, there was further significant impairment. Locomotor activity was affected from second exposure of MPTP, and the impairment increased with third MPTP exposure. Impairment of liver function through increase in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels was observed after first MPTP insult, and it worsened with second and third administrations. First administration of MPTP triggered systemic inflammation showing significant increase in inflammatory markers in the liver. Our data shows for the first time that an intranasal route of entry of MPTP affects liver from the non-motor phase of PD itself, occurring concomitantly with the reduction of striatal dopamine. It also suggests that a single dose is not enough to bring about progression of the disease from non-motor to locomotor deficiency, and a repeated dose is needed to establish the motor severity phase in the rat intranasal MPTP model.

Locus coeruleus-CA1 projections are involved in chronic depressive stress-induced hippocampal vulnerability to transient global ischaemia

Depression and transient ischaemic attack represent the common psychological and neurological diseases, respectively, and are tightly associated. However, studies of depression-affected ischaemic attack have been limited to epidemiological evidences, and the neural circuits underlying depression-modulated ischaemic injury remain unknown. Here, we find that chronic social defeat stress (CSDS) and chronic footshock stress (CFS) exacerbate CA1 neuron loss and spatial learning/memory impairment after a short transient global ischaemia (TGI) attack in mice. Whole-brain mapping of direct outputs of locus coeruleus (LC)-tyrosine hydroxylase (TH, Th:) positive neurons reveals that LC-CA1 projections are decreased in CSDS or CFS mice. Furthermore, using designer receptors exclusively activated by designer drugs (DREADDs)-based chemogenetic tools, we determine that Th:LC-CA1 circuit is necessary and sufficient for depression-induced aggravated outcomes of TGI. Collectively, we suggest that Th:LC-CA1 pathway plays a crucial role in depression-induced TGI vulnerability and offers a potential intervention for preventing depression-related transient ischaemic attack.

Comparative Behavioral Correlation of High and Low-Performing Mice in the Forced Swim Test

Behavioral analysis in mice provided important contributions in helping understand and treat numerous neurobehavioral and neuropsychiatric disorders. The behavioral performance of animals and humans is widely different among individuals but the neurobehavioral mechanism of the innate difference is seldom investigated. Many neurologic conditions share comorbid symptoms that may have common pathophysiology and therapeutic strategy. The forced swim test (FST) has been commonly used to evaluate the "antidepressant" properties of drugs yet the individual difference analysis of this test was left scantly investigated along with the possible connection among other behavioral domains. This study conducted an FST-screening in outbred CD-1 male mice and segregated them into three groups: high performers (HP) or the active swimmers, middle performers (MP), and low performers (LP) or floaters. After which, a series of behavioral experiments were performed to measure their behavioral responses in the open field, elevated plus maze, Y maze, three-chamber social assay, novel object recognition, delay discounting task, and cliff avoidance reaction. The behavioral tests battery revealed that the three groups displayed seemingly correlated differences in locomotor activity and novel object recognition but not in other behaviors. This study suggests that the HP group in FST has higher locomotor activity and novelty-seeking tendencies compared to the other groups. These results may have important implications in creating behavior database in animal models that could be used for predicting interconnections of various behavioral domains, which eventually helps to understand the neurobiological mechanism controlling the behaviors in individual subjects.

Modulation of the neurotransmitter systems through the anti-inflammatory and antidepressant-like effects of squalene from Aurantiochytrium sp

Although algae have been the focal point of biofuel research, studies on their biological activities have been limited. In recent years, however, the importance of algae as sources of functional ingredients has been recognized due to their health beneficial effects. In this study, we evaluated the antidepressant-like activities of ethanol extract of Aurantiochytrium sp. (EEA) in the forced swimming test (FST)-induced depression in ICR mice. Imipramine, a commercially available tricyclic antidepressant drug, was used as positive control. Animals were administered EEA orally for 14 consecutive days and were subjected to the locomotor activity testing. Additionally, changes in gene expression in mice brain were assessed by real-time PCR and microarray assays to understand the molecular mechanisms underlying the effect of EEA. We found that the immobility time in FST was significantly reduced in the EEA-treated mice compared to that of in the control mice. Microarray and real-time PCR results revealed that EEA treatment induced changes in several genes in mice brain associated with pro-inflammation and dopaminergic, cholinergic, glutamatergic, and serotonergic synapses. It has previously been reported that several cytokines, such as IL-6 and TNF-α, which mediate neuroinflammation, are also responsible for indirectly altering brain neurotransmitter levels in neuropsychiatric disorders. Therefore, the regulation of the expression of pro-inflammatory genes in EEA-administered mice brain is considered to contribute to the enhancement of neurotransmitter systems-related gene expression in our study. Moreover, our in vitro study suggested that squalene, a component produced by Aurantiochytrium, was one of the active substances in EEA. In conclusion, our study provides the first evidence that Aurantiochytrium sp. can reduce neuroinflammation that may contribute to the modulation of the neurotransmitter systems, which could underlie its antistress and antidepressant effects.