Identifying fast-onset antidepressants using rodent models

Evaluation of behavioural and neurochemical effects of psilocybin in mice subjected to chronic unpredictable mild stress

Depression and anxiety are disabling and high incidence mental disorders characterized by phenotypic heterogeneity. Currently available treatments show severe limitations. Thus, there is an urgent need for effective treatments in this population. In the search for novel rapid-acting antidepressants, the psychedelic psilocybin has emerged as a promising therapy in several clinical trials. However, its antidepressant mechanism of action is still not well understood. The aim of the present study was to evaluate the therapeutic potential of psilocybin in ameliorating the adverse behavioural and neurochemical consequences of chronic stress. To this end, a chronic unpredictable mild stress (CUMS) animal model was used, and psilocybin treatment was administered (two doses of 1 mg/kg, i.p., administered 7 days apart). Psilocybin reversed impairments in anhedonia and behavioural despair dimensions of depressive phenotype but not in apathy-related behaviour. Psilocybin administration was also able to exert an anxiolytic-like effect on treated animals. Physiological alterations caused by stress, indicative of a hyperactive hypothalamic-pituitary-adrenal axis (HPA), were not reversed by psilocybin. When neuroplasticity-related proteins were assessed in cerebral cortex, brain-derived neurotrophic factor (BDNF) was found to be decreased in stressed animals, and treatment did not reverse such impairment. Psilocybin administration increased the expression and function of serotonin-2A-receptor (5HT2AR) in brain cortex of control and CUMS groups. Furthermore, psilocybin treatment caused a selective increase in the expression of glucocorticoid-receptor (GR) in brain cortex of CUMS mice. In conclusion, psilocybin was able to rescue impairments in the depressive phenotype, and to induce anxiolytic-like effects. Furthermore, an enhancement in sensitivity to psilocybin-induced HTR was observed following a booster dose. Altogether, this work provides new knowledge on the putative benefit/risk actions of psilocybin and contributes to the understanding of the therapeutic mechanism of action of psychedelics.

Activation patterns in male and female forebrain areas during habituation to food and context novelty

Novelty has significant effects on feeding behavior. New foods and unfamiliar environments suppress consumption, and adaptation to novelty is fundamental to survival. Yet, little is known about habituation to eating in a novel environment. The aim of the current study was to determine if context familiarity impacts habituation to novel food and to identify underlying neural substrates. Adult male and female rats were tested for consumption of a novel, palatable food in a novel or familiar environment across four habituation sessions and a final test session. Test-induced Fos expression was measured in amygdalar, thalamic, prefrontal, and hippocampal regions known to be recruited during the first exposure to novelty. Rats in the novel context ate less compared to rats in the familiar context during each habituation session and test, and females ate less than males during the first session. Habituation to eating in the novel context robustly induced Fos in the majority of regions analyzed, including the central, basolateral, and basomedial nuclei of the amygdala, thalamic paraventricular and reuniens nuclei, and the hippocampal field CA1. Females had overall higher Fos induction in most regions analyzed and higher in the novel condition in the reuniens nucleus. Bivariate correlation analyses of Fos induction between regions found a large number of correlations in the novel context condition. Females tested in the novel context had uniquely large number of correlations between all regions analyzed, except for one thalamic subregion. These results suggest that novelty from context remains relevant late in habituation and recruits a distinct and more interactive network in females than in males.

Neuroimaging pattern interactions for suicide risk in depression captured by ensemble learning over transcriptome-defined parcellation

BACKGROUND

For suicide in major depression disorder, it is urgent to seek for a reliable neuroimaging biomarker with interpretable links to molecular tissue signatures. Accordingly, we developed an ensemble learning scheme over transcriptome-defined parcellations (TDP) to explore homogeneously parcellated brain patterns and their interactions.

METHODS

96 depressed patients without suicide attempt (SA), 86 with SA and 102 healthy controls were recruited for resting state fMRI scanning. Six genetic dimensions were created by homogenous transcriptomic delineations from Allen Human Brain Atlas. Spatially-continuous TDPs were generated according to expression-levels of each brain region along diverse dimensions. Subsequently, TDPs were integrated with a three-layer ensemble learning scheme, where brain dysfunction of each TDP related to suicide was quantified with a resting-state functional abnormality (RSFA) score. Then, personalized index of brain dysfunction was produced according to the interactive pattern across TDPs.

RESULTS

Ensemble learning over TDPs displayed higher suicide predictive performance, relative to that over the regions level, and over null model (95 % CI of accuracy: 73.23 ± 1.07 %; 64.59 ± 3.00 %; 65.41 ± 3.97 %, respectively). Empowered by specific parieto-occipital TDP (PO-TDP) pattern quantified with RSFA score in suicide risk prediction, its alternations of SA effects were spatially associated with transcriptional profiles of GRIN2A and GABRG2. Moreover, glutamatergic and GABAergic synapse were overrepresented in enrichment analysis.

CONCLUSION

Glutamatergic and GABAergic dysfunction in the visual cortex was suggested via the PO-TDP specific interaction pattern. The inherent excitatory/inhibitory imbalance could contribute to aberrant emotional processing and neurocognitive impairment, ultimately leading to suicide.

Music therapy as a preventive intervention for postpartum depression: modulation of synaptic plasticity, oxidative stress, and inflammation in a mouse model

Postpartum depression (PPD) significantly impacts women's mental health and social functioning, yet effective therapies remain limited. This study investigates the preventive effects of music therapy on PPD-like behaviors and the underlying neurobiological mechanisms in a mouse model subjected to ovarian hormone withdrawal (HW). Mice exposed to daily music sessions exhibited markedly reduced depression- and anxiety-like behaviors, as evidenced by enhanced performance in behavioral tests such as the open field test (OFT), forced swim test (FST), elevated plus maze test (EPM), sucrose preference test (SPT), novelty-suppressed feeding (NSF) test, and tail suspension test (TST). Furthermore, music therapy normalized oxidative stress indicators (NO, MDA, SOD, CAT, GSH-Px, T-AOC, ATP, and glutamate) in the serum, hippocampus, and prefrontal cortex. Additionally, music exposure reduced levels of proinflammatory factors (IL-6, IL-1β, iNOS, TNF-α, and TGF-β) and the activation of microglia and astrocytes in these brain regions. Notably, music therapy preserved neuronal integrity, promoted neurogenesis, and maintained synaptic plasticity, evidenced by the restoration of dendritic spines. Transcriptome sequencing identified differential gene expression in pathways related to synaptic plasticity, inflammation, and oxidative stress. These findings suggest that music therapy prevents PPD by modulating oxidative stress, inflammation, and synaptic integrity, providing robust preclinical evidence for its potential as a natural preventive intervention for PPD. This study underscores the need for further clinical research to validate the therapeutic efficacy of music in preventing PPD in humans, highlighting its promise as a non-invasive and accessible treatment modality.

Neuroprotection vs. Neurotoxicity: The Dual Impact of Brain Lipids in Depression

Growing neurochemical evidence highlights cerebral lipid dysregulation as a key factor in the pathophysiology of major depressive disorder (MDD). This review systematically explores the dual roles of lipid species in both normal behavioral regulation and MDD development. By critically examining the recent literature, we classify these lipid species into two functional categories based on their functional neuroactivity: (1) neuroprotective lipids (sphingomyelin, cholesterol, cardiolipin, sphingosine, phosphatidic acid, and phosphatidylserine), which exert neuroprotective effects by modulating membrane fluidity and supporting synaptic vesicle trafficking; and (2) neurotoxic lipids (ceramides, phosphatidylinositol, phosphocholine, and phosphatidylethanolamine), which promote apoptotic signaling cascades and disrupt mitochondrial bioenergetics. An unresolved but critical question pertains to the maintenance of homeostatic equilibrium between these opposing lipid classes. This balance is essential, given their significant impact on membrane protein localization and function, monoaminergic neurotransmitter metabolism, energy homeostasis, and redox balance in neural circuits involved in mood regulation. This emerging framework positions cerebral lipidomics as a promising avenue for identifying novel therapeutic targets and developing biomarker-based diagnostic approaches for MDD treatment.

Chronic treatment of mixture of two iridoids proportional to prescriptional dose of Yueju improves hippocampal PACAP-related neuroinflammation and neuroplasticity signaling in the LPS-induced depression model

ETHNOPHARMACOLOGICAL RELEVANCE

Geniposide (GP) and shanzhiside methyl ester (SM) are the two important bioactive compounds in the classical traditional Chinese herbal medicine Yueju Pill, which is currently used as an over-the-counter (OTC) medicine in China. Yueju has been demonstrated with antidepressant-like effects with the prescriptional dose. As GP and SM both have antidepressant potential, the synergism of them could be crucial to the function of Yueju.

OBJECTIVES

The neuropeptide pituitary adenylyl cyclase-activating polypeptide (PACAP) has been implicated in the onset of antidepressant-like response. Here we investigated the synergism of the chronic treatment with GP and SM, at proportional doses to Yueju, on antidepressant-like effects, and underlying mechanism of PACAP-related signaling in a neuroinflammation-based depression model.

MATERIALS AND METHODS

Depression-related behaviors were tested in the lipopolysaccharide (LPS)-induced depression model. The molecular signaling of neuroinflammation and neuroplasticity was investigated using Western blot analysis, immunofluorescence and pharmacological inhibition of mTOR signaling.

RESULTS

Chronic treatment of GP and SM (GS) at the dose which is proportional to the prescriptional dose of Yueju synergistically elicited antidepressant-like effects. Chronic treatment of the GS or the conventional antidepressant fluoxetine (FLX) showed antidepressant-like effects in LPS-injected mice. In vitro analysis indicated the synergism of GS on PACAP expression. In the hippocampus of LPS-injected mice, both GS and FLX enhanced PACAP expression, downregulated the inflammatory signaling of Iba-1/NF-кB/IL-1β and NLRP3, and upregulated the neuroplasticity signaling of mTOR-BDNF/PSD95. Additionally, both treatments reduced microglia activation indicated by Iba-1 immunofluorescent staining. Rapamycin, an mTOR inhibitor, blunted the antidepressant-like effects and the upregulation of BDNF expression induced by chronic GS.

CONCLUSION

The antidepressant-like effects elicited by chronic fluoxetine or by synergistic doses of GS were involved in the upregulation of hippocampal PACAP levels, in association with ameliorated neuroinflammation and neuroplasticity signaling in LPS-injected mice. GS synergism may play a key part in the antidepressant-like effects of the prescriptional dose of Yueju.

Bidirectional relationship between sleep and depression

Patients with depression almost inevitably exhibit abnormalities in sleep, such as shortened latency to enter rapid eye movement (REM) sleep and decrease in electroencephalogram delta power during non-REM sleep. Insufficient sleep can be stressful, and the accumulation of stress leads to the deterioration of mental health and contributes to the development of psychiatric disorders. Thus, it is likely that depression and sleep are bidirectionally related, i.e. development of depression contributes to sleep disturbances and vice versa. However, the relation between depression and sleep seems complicated. For example, acute sleep deprivation can paradoxically improve depressive symptoms. Thus, it is difficult to conclude whether sleep has beneficial or harmful effects in patients with depression. How antidepressants affect sleep in patients with depression might provide clues to understanding the effects of sleep, but caution is required considering that antidepressants have diverse effects other than sleep. Recent animal studies support the bidirectional relation between depression and sleep, and animal models of depression are expected to be beneficial for the identification of neuronal circuits that connect stress, sleep, and depression. This review provides a comprehensive overview regarding the current knowledge of the relationship between depression and sleep.

Sugemule-7 alleviates oxidative stress, neuroinflammation, and cell death, promoting synaptic plasticity recovery in mice with postpartum depression

Postpartum depression (PPD) profoundly impacts the mental and physical health of women globally and is an incurable psychological disorder. Traditional pharmacological treatments often have strong side effects and may adversely affect infant health through breastfeeding, underscoring the critical need for natural and gentle treatment strategies. Sugemule-7, a traditional Chinese medicine comprising multiple natural plant ingredients, represents a potentially safer and more effective alternative. To investigate its preventive effects on PPD, we established an animal model and administered the drug Sugemule-7. Our study demonstrated that varying doses of Sugemule-7 effectively alleviated depressive and anxiety-like behaviors in PPD mice, as assessed through a battery of tests, including the open field test, tail suspension test, sucrose preference test, forced swim test, novelty-suppressed feeding test, and elevated plus maze test. Furthermore, Sugemule-7 significantly improved oxidative stress levels in the serum, prefrontal cortex, and hippocampus of PPD-induced mice while also suppressing inflammatory responses and abnormal neuronal death in these brain regions. Transcriptomic sequencing of hippocampal and prefrontal cortex tissues supported our findings, revealing that differential gene expression is primarily involved in regulating synaptic plasticity. Overall, our study confirms the efficacy of Sugemule-7 in treating PPD at different concentrations, potentially alleviating depressive behaviors by enhancing synaptic plasticity, mitigating oxidative stress, reducing inflammation, and protecting neurons.

Hindbrain networks: Exploring the hidden anxiety circuits in rodents

Anxiety disorders are multifaceted conditions that engage numerous brain regions and circuits. While the hindbrain is pivotal in fundamental biological functions, its role in modulating emotions has been underappreciated. This review will uncover critical targets and circuits within the hindbrain that are essential for both anxiety and anxiolytic effects, expanding on research obtained through behavioral tests. The bidirectional neural pathways between the hindbrain and other brain regions, with a spotlight on vagal afferent signaling, provide a crucial framework for unraveling the neural mechanisms underlying anxiety. Exploring neural circuits within the hindbrain can help to unravel the neurobiological mechanisms of anxiety and elucidate differences in the expression of these circuits between genders, thereby providing valuable insights for the development of future anxiolytic drugs.

Brain region-specific roles of brain-derived neurotrophic factor in social stress-induced depressive-like behavior

Brain-derived neurotrophic factor is a key factor in stress adaptation and avoidance of a social stress behavioral response. Recent studies have shown that brain-derived neurotrophic factor expression in stressed mice is brain region-specific, particularly involving the corticolimbic system, including the ventral tegmental area, nucleus accumbens, prefrontal cortex, amygdala, and hippocampus. Determining how brain-derived neurotrophic factor participates in stress processing in different brain regions will deepen our understanding of social stress psychopathology. In this review, we discuss the expression and regulation of brain-derived neurotrophic factor in stress-sensitive brain regions closely related to the pathophysiology of depression. We focused on associated molecular pathways and neural circuits, with special attention to the brain-derived neurotrophic factor-tropomyosin receptor kinase B signaling pathway and the ventral tegmental area-nucleus accumbens dopamine circuit. We determined that stress-induced alterations in brain-derived neurotrophic factor levels are likely related to the nature, severity, and duration of stress, especially in the above-mentioned brain regions of the corticolimbic system. Therefore, BDNF might be a biological indicator regulating stress-related processes in various brain regions.

Laser-Induced Olfactory Bulbectomy in Adult Zebrafish as a Novel Putative Model for Affective Syndrome: A Research Tribute to Brian Leonard

Inducing multiple neurobehavioural and neurochemical deficits, olfactory bulbectomy (OBX) has been developed as a rodent model of depression with potential for antidepressant drug screening. However, the generality of this model in other vertebrate taxa remains poorly understood. A small freshwater teleost fish, the zebrafish (Danio rerio), is rapidly becoming a common model species in neuroscience research. Capitalizing on a recently developed model of noninvasive targeted laser ablation of zebrafish brain, here we report an OBX model in adult fish. An easy-to-perform noninvasive method of inducing affective syndrome-like behavioural deficits in fish, it extends the generality of OBX to other taxa beyond mammals, also offering several practical advantages and novel lines of research in experimental modelling of CNS disorders. The work is a scientific tribute to the legacy of Brian Leonard (1936-2023), a great friend and a brilliant scientist who introduced OBX as a rodent model for affective pathobiology and whose advice and encouragement have inspired the present study.

Circadian desynchrony in early life leads to enduring autistic-like behavioral changes in adulthood

Circadian rhythm regulates a variety of biological processes in almost all living organisms. Modern lifestyles, e.g. transmeridian travel, night shift, light at night, etc., frequently disrupt people's regular sleep-wake cycles and create a misalignment (circadian desynchrony) between the natural environment and the endogenous body clock, and between different circadian oscillators within the body. The long-term consequences of circadian desynchrony on neurodevelopment and adult behavior remain elusive. Increasing clinical evidence supports a correlation between the disruption of the circadian system and neurodevelopmental disorders, such as autism spectrum disorders. Despite clinical correlations, experimental evidence is yet to establish a link between circadian disturbance in early life and adult behavioral changes. Here, using a "short day" (SD) mouse model, in which mice were exposed to an 8 h/8 h light/dark (LD) cycle mimicking a "shift work" schedule from gestation day 1 to postnatal day 21, we performed a battery of behavioral tests to assess changes in adult behaviors, including sociability, affective behaviors, stereotypy, cognition and locomotor functions. In contrast to the control mice kept in a 12 h/12 h LD cycle, the adult SD mice entrained to the 8 h/8 h LD cycle, but their free running rhythms remained normal in constant darkness. Interestingly, however, the SD mice displayed diminished sociability, a reduced preference for social novelty, excessive repetitive behaviors, and compromised cognitive functions, all of which resemble characteristics of autism-like behavioral alterations. In addition, the SD mice exhibited significant anxiety- and depressive-like behaviors and impaired motor functions. By western blotting and immunostaining analyses, hyperactivation of the mTORC1/S6K1 pathway was detected in multiple forebrain regions of SD mice. These findings underscore the enduring impact of early-life circadian disruption on neurochemical signaling and behavioral patterns into adulthood, highlighting a pivotal role for circadian regulation in neurodevelopment.

Hypoxanthine Produces Rapid Antidepressant Effects by Suppressing Inflammation in Serum and Hippocampus

The occurrence and development of depression are closely related to disorders of the brain and peripheral substances. Abnormal metabolites in the blood affect the signal regulation function of the nerve center, which is one of the key factors for depression episodes. This study was focused on metabolites in serum and the mechanism of its antidepressant in the hippocampus. In the present study, serum metabolites in patients with depression were screened by metabolomic techniques. Various depressive mouse models and behavioral tests were used to assess its antidepressant effects. The expressions of inflammatory signaling were detected by using Western blot, ELISA, and immunofluorescence. We found that the metabolite hypoxanthine in the serum of patients with depression was significantly reduced, and the same result was also found in two mouse models of depression such as chronic unpredictable mild stress (CUMS) and social defeat stress (SD). By administering different doses of hypoxanthine (5, 10, 15 mg/kg), we found that only 15 mg/kg was able to significantly reduce the latency and increase food consumption in the novelty suppressed-feeding test (NSF), which was also able to reverse the depressive phenotypes of mice in the CUMS model after a single administration at 2 h later. Hypoxanthine obviously reduced the expressions of inflammation in serum and downregulated the expressions of MAPK and NLRP3-related pathways in the hippocampus in CUMS mice. Moreover, hypoxanthine also suppressed the activations of glial cells including GFAP and IBA-1 in hippocampal CA1, CA3, and dentate gyrus (DG). To sum up, hypoxanthine exerted antidepressant effect relying on the inhibition of peripheral and hippocampal inflammations by regulating MAPK, NLRP3-related pathways, and glial cells. This was the first time that we have found a disordered metabolite in patients with depression and further systematically demonstrated its efficacy and potential mechanism of antidepressants, providing new ideas for antidepressant drug development.

DSP-6745, a novel 5-hydroxytryptamine modulator with rapid antidepressant, anxiolytic, antipsychotic and procognitive effects

BACKGROUND

Current treatment of major depressive disorder is facing challenges, including a low remission rate, late onset of efficacy, and worsening severity due to comorbid symptoms such as psychosis and cognitive dysfunction. Serotonin (5-HT) neurotransmission is involved in a wide variety of psychiatric diseases and its potential as a drug target continues to attract attention.

OBJECTIVES

The present study elucidates the effects of a novel 5-HT modulator, DSP-6745, on depression and its comorbid symptoms.

RESULTS

In vitro radioligand binding and functional assays showed that DSP-6745 is a potent inhibitor of 5-HT transporter and 5-HT2A, 5-HT2C, and 5-HT7 receptors. In vivo, DSP-6745 (6.4 and 19.1 mg/kg as free base, p.o.) increased the release of not only 5-HT, norepinephrine, and dopamine, but also glutamate in the medial prefrontal cortex. The results of in vivo mouse phenotypic screening by SmartCube® suggested that DSP-6745 has a behavioral signature combined with antidepressant-, anxiolytic-, and antipsychotic-like signals. A single oral dose of DSP-6745 (6.4 and 19.1 mg/kg) showed rapid antidepressant-like efficacy in the rat forced swim test, even at 24 h post-dosing, and anxiolytic activity in the rat social interaction test. Moreover, DSP-6745 (12.7 mg/kg, p.o.) led to an improvement in the apomorphine-induced prepulse inhibition deficit in rats. In the marmoset object retrieval with detour task, which is used to assess cognitive functions such as attention and behavioral inhibition, DSP-6745 (7.8 mg/kg, p.o.) enhanced cognition.

CONCLUSIONS

These data suggest that DSP-6745 is a multimodal 5-HT receptor antagonist and a 5-HT transporter inhibitor and has the potential to be a rapid acting antidepressant with efficacies in mitigating the comorbid symptoms of depression.

Histone 3 Trimethylation Patterns are Associated with Resilience or Stress Susceptibility in a Rat Model of Major Depression Disorder

Major Depressive Disorder (MDD) is a severe and multifactorial psychiatric condition. Evidence has shown that environmental factors, such as stress, significantly explain MDD pathophysiology. Studies have hypothesized that changes in histone methylation patterns are involved in impaired glutamatergic signaling. Based on this scenario, this study aims to investigate histone 3 involvement in depression susceptibility or resilience in MDD pathophysiology by investigating cellular and molecular parameters related to i) glutamatergic neurotransmission, ii) astrocytic functioning, and iii) neurogenesis. For this, we subjected male Wistar rats to the Chronic Unpredictable Mild Stress (CUMS) model of depression. We propose that by evaluating the sucrose consumption, open field, and object recognition test performance from animals submitted to CUMS, it is possible to predict with high specificity rats with susceptibility to depressive-like phenotype and resilient to the depressive-like phenotype. We also demonstrated, for the first time, that patterns of H3K4me3, H3K9me3, H3K27me3, and H3K36me3 trimethylation are strictly associated with the resilient or susceptible to depressive-like phenotype in a brain-region-specific manner. Additionally, susceptible animals have reduced DCx and GFAP and resilient animals present increase of AQP-4 immunoreactivity. Together, these results provide evidence that H3 trimethylations are related to the development of the resilient or susceptible to depressive-like phenotype, contributing to further advances in the pathophysiology of MDD and the discovery of mechanisms behind resilience.

Pharmacological inhibition of Kir4.1 evokes rapid-onset antidepressant responses

Major depressive disorder, a prevalent and severe psychiatric condition, necessitates development of new and fast-acting antidepressants. Genetic suppression of astrocytic inwardly rectifying potassium channel 4.1 (Kir4.1) in the lateral habenula ameliorates depression-like phenotypes in mice. However, Kir4.1 remains an elusive drug target for depression. Here, we discovered a series of Kir4.1 inhibitors through high-throughput screening. Lys05, the most potent one thus far, effectively suppressed native Kir4.1 channels while displaying high selectivity against established targets for rapid-onset antidepressants. Cryogenic-electron microscopy structures combined with electrophysiological characterizations revealed Lys05 directly binds in the central cavity of Kir4.1. Notably, a single dose of Lys05 reversed the Kir4.1-driven depression-like phenotype and exerted rapid-onset (as early as 1 hour) antidepressant actions in multiple canonical depression rodent models with efficacy comparable to that of (S)-ketamine. Overall, we provided a proof of concept that Kir4.1 is a promising target for rapid-onset antidepressant effects.

Recruitment of hippocampal and thalamic pathways to the central amygdala in the control of feeding behavior under novelty

It is adaptive to restrict eating under uncertainty, such as during habituation to novel foods and unfamiliar environments. However, sustained restrictive eating can become maladaptive. Currently, the neural substrates of restrictive eating are poorly understood. Using a model of feeding avoidance under novelty, our recent study identified forebrain activation patterns and found evidence that the central nucleus of the amygdala (CEA) is a core integrating node. The current study analyzed the activity of CEA inputs in male and female rats to determine if specific pathways are recruited during feeding under novelty. Recruitment of direct inputs from the paraventricular nucleus of the thalamus (PVT), the infralimbic cortex (ILA), the agranular insular cortex (AI), the hippocampal ventral field CA1, and the bed nucleus of the stria terminals (BST) was assessed with combined retrograde tract tracing and Fos induction analysis. The study found that during consumption of a novel food in a novel environment, larger number of neurons within the PVTp and the CA1 that send monosynaptic inputs to the CEA were recruited compared to controls that consumed familiar food in a familiar environment. The ILA, AI, and BST inputs to the CEA were similarly recruited across conditions. There were no sex differences in activation of any of the pathways analyzed. These results suggest that the PVTp-CEA and CA1-CEA pathways underlie feeding inhibition during novelty and could be potential sites of malfunction in excessive food avoidance.

HMGB1/STAT3/p65 axis drives microglial activation and autophagy exert a crucial role in chronic Stress-Induced major depressive disorder

INTRODUCTION

Neuroinflammation and autophagy are implicated in stress-related major depressive disorder (MDD), but the underlying molecular mechanisms remain largely unknown.

OBJECTIVES

Here, we identified that MDD regulated by HMGB1/STAT3/p65 axis mediated microglial activation and autophagy for the first time. Further investigations were performed to uncover the effects of this axis on MDD in vivo and in vitro.

METHODS

Bioinformatics analyses were used to re-analysis the transcriptome data from the dorsolateral prefrontal cortex (dlPFC) of post-mortem male MDD patients. The expression level of HMGB1 and its correlation with depression symptoms were explored in MDD clinical patients and chronic social defeat stress (CSDS)-induced depression model mice. Specific adeno-associated virus and recombinant (r)HMGB1 injection into the medial PFC (mPFC) of mice, and pharmacological inhibitors with rHMGB1 in two microglial cell lines exposed to lipopolysaccharide were used to analyze the effects of HMGB1/STAT3/p65 axis on MDD.

RESULTS

The differential expression of genes from MDD patients implicated in microglial activation and autophagy regulated by HMGB1/STAT3/p65 axis. Serum HMGB1 level was elevated in MDD patients and positively correlated with symptom severity. CSDS not only induced depression-like states in mice, but also enhanced microglial reactivity, autophagy as well as activation of the HMGB1/STAT3/p65 axis in mPFC. The expression level of HMGB1 was mainly increased in the microglial cells of CSDS-susceptible mice, which also correlated with depressive-like behaviors. Specific HMGB1 knockdown produced a depression-resilient phenotype and suppressed the associated microglial activation and autophagy effects of CSDS-induced. The effects induced by CSDS were mimicked by exogenous administration of rHMGB1 or specific overexpression of HMGB1, while blocked by STAT3 inhibitor or p65 knockdown. In vitro, inhibition of HMGB1/STAT3/p65 axis prevented lipopolysaccharide-induced microglial activation and autophagy, while rHMGB1 reversed these changes.

CONCLUSION

Our study established the role of microglial HMGB1/STAT3/p65 axis in mPFC in mediating microglial activation and autophagy in MDD.

The anti-depression effect and potential mechanism of the petroleum ether fraction of CDB: Integrated network pharmacology and metabolomics

The combination of Chaidangbo (CDB) is an antidepressant traditional Chinese medicine (TCM) prescription simplified by Xiaoyaosan (a classic antidepressant TCM prescription) through dismantling research, which has the effect of dispersing stagnated liver qi and nourishing blood in TCM theory. Although the antidepressant effect of CBD has been confirmed in animal studies, the material basis and possible molecular mechanism for antidepressant activity in CBD have not been clearly elucidated. Herein, we investigated the effects and potential mechanisms of CDB antidepressant fraction (petroleum ether fraction of CDB, PEFC) on chronic unpredictable mild stress (CUMS)-induced depression-like behavior in mice using network pharmacology and metabolomics. First, a UPLC-QE/MS was employed to identify the components of PEFC. To extract active ingredients, SwissADME screening was used to the real PEFC components that were found. Potential PEFC antidepressant targets were predicted based on a network pharmacology approach, and a pathway enrichment analysis was performed for the predicted targets. Afterward, a CUMS mouse depression model was established and LC-MS-based untargeted hippocampal metabolomics was performed to identify differential metabolites, and related metabolic pathways. Finally, the protein expressions in mouse hippocampi were determined by Western blot to validate the network pharmacology and metabolomics deduction. A total of 16 active compounds were screened in SwissADME that acted on 73 core targets of depression, including STAT3, MAPKs, and NR3C1; KEGG enrichment analysis showed that PEFC modulated signaling pathways such as PI3K-Akt signaling pathway, endocrine resistance, and MAPK to exert antidepressant effects. PEFC significantly reversed abnormalities of hippocampus metabolites in CUMS mice, mainly affecting the synthesis and metabolism of glycine, serine, and threonine, impacting catecholamine transfer and cholinergic synapses and regulating the activity of the mTOR signaling pathway. Furthermore, Western blot analysis confirmed that PEFC significantly influenced the main protein levels of the PI3K/Akt/mTOR signaling pathways in the hippocampus of mice subjected to CUMS. This study integrated metabolomics, network pharmacology and biological verification to explore the potential mechanism of PEFC in treating depression, which is related to the regulation of amino acid metabolism dysfunction and the activation of PI3K/Akt/mTOR signaling pathways in the hippocampus. The comprehensive strategy also provided a reasonable way for unveiling the pharmacodynamic mechanisms of multi-components, multi-targets, and multi-pathways in TCM with antidepressant effect.

A high salt intake in early life affects stress-coping response in males but not in female rats

Eating diets high in salt has been associated with alterations in the immune system and the potential development of neuropsychiatric disorders. This area of research shows promise, but there is currently a limited amount of research on this topic. The present study investigated whether a high salt diet (HSD) affects anhedonia and stress-coping response behaviors in young male and female Wistar rats. In this study, male and female Wistar rats were fed an HSD (8 % NaCl w/w) from weaning to post-natal day (PND) 64. From PND 60 to 64, the rats underwent a spontaneous locomotor activity test (SLA), sucrose splash test (SST), sucrose preference test (SPT), and forced swim test (FST), followed by euthanasia at PND 65. Male and female rats consuming the HSD exhibited an increase in water intake compared to the corresponding control diet (CD) groups. Male rats had lower body weight despite having similar food intakes compared to the CD group. Male rats displayed an active stress-coping behavior in the FST, characterized by increased mobility. Additionally, HSD-fed males exhibited a greater preference for sucrose solution in the SPT. However, no effect of diet and sex were detected in the SST and the SLA, and hypothalamic levels of leptin and ghrelin receptors. On the other hand, female rats were less susceptible to the experimental conditions applied in this protocol than males.

Baccharis dracunculifolia DC Consumption Improves Nociceptive and Depressive-like Behavior in Rats with Experimental Osteoarthritis

Osteoarthritis (OA) persistently activates nociceptors, leading to chronic pain, which is often accompanied by the comorbid development of emotional impairments (anxiety and depression), an effect associated with microgliosis. Baccharis dracunculifolia DC (Asteraceae), a Brazilian edible plant, is an important source of active compounds with anti-inflammatory abilities. Thus, we evaluated its ability to reverse OA-induced nociceptive and emotional-like impairments in osteoarthritic ovariectomized female rats using the kaolin/carrageenan (K/C) model. Four weeks after OA induction, mechanical hyperalgesia was confirmed, and the treatment started. Control animals (SHAMs) were treated with phosphate-buffered saline (PBS), while arthritic animals (ARTHs) either received PBS or B. dracunculifolia 50 mg/kg (Bd50) and 100 mg/kg (Bd100), via gavage, daily for five weeks. At the end of the treatment, anxiety-like behavior was assessed using the Open Field Test (OFT), anhedonia was assessed using the Sucrose Preference Test (SPT), and learned helplessness was assessed using the Forced Swimming Test (FST). After occision, microglia were stained with IBA-1 and quantified in brain sections of target areas (prefrontal cortex, amygdala, and periaqueductal grey matter). Treatment with B. dracunculifolia extract reversed OA-induced mechanical hyperalgesia and partly improved depressive-like behavior in OA animals' concomitant to a decrease in the number of M1 microglia. Our findings suggest that B. dracunculifolia extracts can potentially be used in the food industry and for the development of nutraceuticals and functional foods.

Antidepressant-like Effect of the Eburnamine-Type Molecule Vindeburnol in Rat and Mouse Models of Ultrasound-Induced Depression

Vindeburnol (VIND, RU24722, BC19), a synthetic molecule derived from the eburnamine-vincamine alkaloid group, has many neuropsychopharmacological effects, but its antidepressant-like effects are poorly understood and have only been described in a few patents. To reliably estimate this effect, vindeburnol was studied in a model of long-term variable-frequency ultrasound (US) exposure at 20-45 kHz in male Wistar rats and BALB/c mice. Vindeburnol was administered chronically for 21 days against a background of simultaneous ultrasound exposure at a dose of 20 mg/kg intraperitoneally (IP). Using four behavioral tests, the sucrose preference test (SPT), the social interaction test (SIT), the open field test (OFT), and the forced swimming test (FST), we found that the treatment with the compound diminished depression-like symptoms in mice and rats. The compound restored the ultrasound-related reduced sucrose consumption to control levels and increased social interaction time in mice and rats compared with those in ultrasound-exposed animals. Vindeburnol showed contraversive results of horizontal and vertical activity in both species and generally did not increase locomotor activity. At the same time, the compound showed a specific effect in the FST, significantly reducing the immobility time. Moreover, we found an increase in norepinephrine, dopamine, and its metabolite levels in the brainstem, as well as an increase in dopamine, 3-methoxytyramine, and 3,4-dihydroxyphenylacetic acid levels in the striatum. We also observed a statistically significant increase in tyrosine hydroxylase (TH) levels in the region containing the locus coeruleus (LC). We suggest that using its distinct chemical structure and pharmacological activity as a starting point could boost antidepressant drug discovery.

Paternal Prenatal and Lactation Exposure to a High-Calorie Diet Shapes Transgenerational Brain Macro- and Microstructure Defects, Impacting Anxiety-Like Behavior in Male Offspring Rats

Prenatal exposure to high-energy diets (HED) increases the susceptibility to behavioral alterations in the male offspring. We addressed whether prenatal HED primes the transgenerational inheritance of structural brain changes impacting anxiety/depression-like behavior in the offspring. For this, we used female Wistar rats exposed to a HED [cafeteria (CAF) diet, n = 6] or chow [control (CON) n = 6] during development. Anxiety and depression-like behavior were evaluated in filial 1 (F1), filial 2 (F2), and filial 3 (F3) male offspring using the open field (OFT), elevated plus maze, novelty suppressed feeding (NSFT), tail suspension (TST), and forced swimming tests. Structural brain changes were identified by deformation-based morphometry (DBM) and diffusion tensor imaging using ex vivo MRI. We found that the F1, F2, and F3 offspring exposed to CAF diet displayed higher anxious scores including longer feeding latency during the NSFT, and in the closed arms, only F1 offspring showed longer stay on edges during the OFT versus control offspring. DBM analysis revealed that CAF offspring exhibited altered volume in the cerebellum, hypothalamus, amygdala, and hippocampus preserved up to the F3 generation of anxious individuals. Also, F3 CAF anxious exhibited greater fractional anisotropy and axial diffusivity (AD) in the amygdala, greater apparent diffusion coefficient in the corpus callosum, and greater AD in the hippocampus with respect to the control. Our results suggest that prenatal and lactation exposure to HED programs the transgenerational inheritance of structural brain changes related to anxiety-like behavior in the male offspring.

Targeted mutagenesis in mice via an engineered AsCas12f1 system

SpCas9 and AsCas12a are widely utilized as genome editing tools in human cells, but their applications are largely limited by their bulky size. Recently, AsCas12f1 protein, with a small size (422 amino acids), has been demonstrated to be capable of cleaving double-stranded DNA protospacer adjacent motif (PAM). However, low editing efficiency and large differences in activity against different genomic loci have been a limitation in its application. Here, we show that engineered AsCas12f1 sgRNA has significantly improved the editing efficiency in human cells and mouse embryos. Moreover, we successfully generated three stable mouse mutant disease models using the engineered CRISPR-AsCas12f1 system in this study. Collectively, our work uncovers the engineered AsCas12f1 system expands mini CRISPR toolbox, providing a remarkable promise for therapeutic applications.

Rosmarinic acid alleviate CORT-induced depressive-like behavior by promoting neurogenesis and regulating BDNF/TrkB/PI3K signaling axis

Rosmarinic acid (RA), a natural phenolic acid compound with a variety of bioactive properties. However, the antidepressant activity and mechanism of RA remain unclear. The aim of this study is to investigate the effects and potential mechanisms of RA on chronic CORT injection induced depression-like behavior in mice. Male C57BL/6 J mice were intraperitoneally injected with CORT (10 mg/kg) and were orally given RA daily (10 or 20 mg/kg) for 21 consecutive days. In vitro, the HT22 cells were exposed to CORT (200 μM) with RA (12.5, 25 or 50 μM) and LY294002 (a PI3K inhibitor) or ANA-12 (a TrkB inhibitor) treatment. The depression-like behavior and various neurobiological changes in the mice and cell injury and levels of target proteins in vitro were subsequently assessed. Here, RA treatment decreased the expression of p-GR/GR, HSP90, FKBP51, SGK-1 in mice hippocampi. Besides, RA increased the average optical density of Nissl bodies and number of dendritic spines in CA3 region, and enhanced Brdu and DCX expression and synaptic transduction in DG region, as well as up-regulated both the BDNF/TrkB/CREB and PI3K/Akt/mTOR signaling. Moreover, RA reduced structural damage and apoptosis in HT22 cells, increased the differentiation and maturation of them. More importantly, LY294002, but not ANA-12, reversed the effect of RA on GR nuclear translocation. Taken together, RA exerted antidepressant activities by modulating the hippocampal glucocorticoid signaling and hippocampal neurogenesis, which related to the BDNF/TrkB/PI3K signaling axis regulating GR nuclear translocation, provide evidence for the application of RA as a candidate for depression.

Merazin hydrate produces rapid antidepressant effects by activating CaMKII to promote neuronal activities and proliferation in hippocampus

In our previous studies, we demonstrated that merazin hydrate (MH) had rapid antidepressant effects, but the deep mechanism needed to be further investigated. In this study, we used depressive-like model, behavioral tests, molecular biology and pharmacological interventions to reveal the underlying mechanisms of MH's rapid antidepressants. We found that a single administration of MH was able to produce rapid antidepressant effects in chronic unpredictable mild stress (CUMS) exposed mice at 1 day later, similar to ketamine. Moreover, MH could not only significantly up-regulated the expressions of cFOS, but also obviously increased the number of Ki67 positive cells in hippocampal dentate gyrus (DG). Furthermore, we also found that the phosphorylated expression of calcium/calmodulin-dependent protein kinase II (CaMKII) was significantly reduced by CUMS in hippocampus, which was also reversed by MH. In addition, pharmacological inhibition of CaMKII by using KN-93 (a CaMKII antagonist) blocked the MH's up-regulation of cFOS and Ki67 in hippocampal DG. To sum up, this study demonstrated that MH produced rapid antidepressant effects by activating CaMKII to promote neuronal activities and proliferation in hippocampus.

Diosmin ameliorates LPS-induced depression-like behaviors in mice: Inhibition of inflammation and oxidative stress in the prefrontal cortex

Diosmin is a flavone glycoside with a confirmed therapeutic effectiveness on the chronic venous disorders. In this paper, the classical mouse depression model induced by LPS was established to explore the effect of Diosmin on depression. Firstly, we found that Diosmin could inhibit the inflammation and neuronal damage in the prefrontal cortex (PFC) of mice, and thus alleviating the LPS-induced depressive-like behaviors. Specifically, Diosmin treatment significantly suppressed the secretion of pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β), reduced the activation of microglia, and inhibited the expression of NLRP3 inflammasome and its downstream effector caspase-1 in both PFC of mice and BV2 microglial cells exposed to LPS. Then, we demonstrated that pretreatment with Diosmin dramatically suppressed the LPS-induced oxidative stress in the PFC of mice, manifested in the decrease of reactive oxygen species and malondialdehyde while increase of catalase activity. Consistently, Diosmin also alleviated the oxidative stress in BV2 cells exposed to LPS. Finally, we confirmed that Diosmin effectively suppressed the activation of NF-κB signaling pathway in the PFC of LPS-treated mice. Further in vitro experiments also verified that Diosmin could prevent the p65 transposition to nucleus in LPS-treated BV2 cells, suggesting that the antidepressant effects of Diosmin are partially mediated by blocking of NF-κB signaling. Taken together, this study proposes the potential antidepressant effect of Diosmin, which provides useful support to the development of new therapies for depression.

Identification of core genes, critical signaling pathways, and potential drugs for countering BPA-induced hippocampal neurotoxicity in male mice

Although the neurotoxicity of the common chemical bisphenol A (BPA) to the mouse hippocampus has been often reported, the mechanism underlying BPA-induced depression-like behavior in mice remains unclear. We evaluated BPA's role in inducing depressive-like behavior by exposing male mice to different BPA concentrations (0, 0.01, 0.1, and 1 μg/mL) and using the forced swimming test (FST) and tail suspension test (TST). We aimed to identify critical gene and anti-BPA-neurotoxicity compounds using RNA sequencing combined with bioinformatics analysis. Our results showed that 1 μg/mL BPA exposure increased mouse immobility during the FST and TST. Based on BPA-induced hippocampal transcriptome changes, we identified NADH: ubiquinone oxidoreductase subunit AB1 (Ndufab1) as a critical and potential therapeutic target gene, and Ndufab1 mRNA and protein levels were downregulated in the BPA-exposed groups. Furthermore, molecular docking identified phenelzine as a compound that could counteract BPA-related neurotoxicity. Conclusively, our analyses confirmed that BPA triggers depressive behavior in male mice by downregulating Ndufab1 expression and suggested that phenelzine might reduce BPA-induced neurotoxicity.

Reduction of BDNF Levels and Biphasic Changes in Glutamate Release in the Prefrontal Cortex Correlate with Susceptibility to Chronic Stress-Induced Anhedonia

Chronic stress has been considered to induce depressive symptoms, such as anhedonia, particularly in susceptible individuals. Synaptic plasticity in the prefrontal cortex (PFC) is closely associated with susceptibility or resilience to chronic stress-induced anhedonia. However, effects of chronic stress with different durations on the neurobiological mechanisms that underlie susceptibility to anhedonia remain unclear. The present study investigated effects of chronic mild stress (CMS) for 14, 21, and 35 d on anhedonia-like behavior and glutamate synapses in the PFC. We found that brain-derived neurotrophic factor (BDNF) levels in the PFC significantly decreased only in anhedonia-susceptible rats that were exposed to CMS for 14, 21, and 35 d. Additionally, 14 d of CMS increased prefrontal glutamate release, and 35 d of CMS decreased glutamate release, in addition to reducing synaptic proteins and spine density in the PFC. Moreover, we found that anhedonia-like behavior in a subset of rats spontaneously decreased, accompanied by the restoration of BDNF levels and glutamate release, on day 21 of CMS. Ketamine treatment restored the reduction of BDNF levels and biphasic changes in glutamate release that were induced by CMS. Our findings revealed a progressive reduction of synaptic plasticity and biphasic changes in glutamate release in the PFC during CMS. Reductions of BDNF levels may be key neurobiological markers of susceptibility to stress-induced anhedonia.

The 5-HT1A receptor biased agonists, NLX-204 and NLX-101, display ketamine-like RAAD and anti-TRD activities in rat CMS models

OBJECTIVES

NLX-101 and NLX-204 are highly selective serotonin 5-HT1A 'biased' agonists, displaying potent and efficacious antidepressant-like activity upon acute administration in models such as the forced swim test.

METHODS

we compared the effects of repeated administration of NLX-101, NLX-204 and ketamine in the chronic mild stress (CMS) model of depression, considered to have high translational potential, on sucrose consumption (anhedonia measure), novel object recognition (NOR; working memory measure) and elevated plus maze (EPM; anxiety measure) in male Wistar and Wistar-Kyoto rats (the latter being resistant to classical antidepressants).

RESULTS

in Wistar rats, NLX-204 and NLX-101 (0.08-0.16 mg/kg i.p.), like ketamine (10 mg/kg i.p.) dose-dependently reversed CMS-induced sucrose intake deficit from treatment Day 1, with nearly full reversal observed at the higher dose at Days 8 and 15. These effects persisted for 3 weeks following treatment cessation. In the NOR test, both doses of NLX-101/NLX-204, and ketamine, rescued the deficit in discrimination index caused by CMS on Days 3 and 17; all three compounds increased time spent in open arms (EPM) but only NLX-204 achieved statistical significance on Days 2 and 16. In Wistar-Kyoto rats, all 3 compounds were also active in the sucrose test and, to a lesser extent, in the NOR and EPM. In non-stressed rats (both strains), the three compounds produced no significant effects in all tests.

CONCLUSIONS

these observations further strengthen the hypothesis that biased agonism at 5-HT1A receptors constitutes a promising strategy to achieve rapid-acting/sustained antidepressant effects combined with activity against TRD, in addition to providing beneficial effects against memory deficit and anxiety in depressed patients.

Music prevents stress-induced depression and anxiety-like behavior in mice

Depression is the most prevalent psychiatric disorder worldwide and remains incurable; however, there is little research on its prevention. The leading cause of depression is stress, and music has been hypothesized to alleviate stress. To examine the potential beneficial effects of music on stress and depression, we subjected mice to chronic unpredictable mild stress (CUMS) during the day and music at night. Strikingly, our results indicated that music completely prevented CUMS-induced depression and anxiety-like behaviors in mice, as assessed by the open field, tail suspension, sucrose preference, novelty suppressed feeding, and elevated plus maze tests. We found that listening to music restored serum corticosterone levels in CUMS mice, which may contribute to the beneficial effects of music on the mouse brain, including the restoration of BDNF and Bcl-2 levels. Furthermore, listening to music prevented CUMS-induced oxidative stress in the serum, prefrontal cortex, and hippocampus of mice. Moreover, the CUMS-induced inflammatory responses in the prefrontal cortex and hippocampus of mice were prevented by listening to music. Taken together, we have demonstrated for the first time in mice experiments that listening to music prevents stress-induced depression and anxiety-like behaviors in mice. Music may restore hypothalamus-pituitary-adrenal axis homeostasis, preventing oxidative stress, inflammation, and neurotrophic factor deficits, which had led to the observed phenotypes in CUMS mice.

Recruitment of Hippocampal and Thalamic Pathways to the Central Amygdala in the Control of Feeding Behavior Under Novelty

It is adaptive to restrict eating under uncertainty, such as during habituation to novel foods and unfamiliar environments. However, sustained restrictive eating is a core symptom of eating disorders and has serious long-term health consequences. Current therapeutic efforts are limited, because the neural substrates of restrictive eating are poorly understood. Using a model of feeding avoidance under novelty, our recent study identified forebrain activation patterns and found evidence that the central nucleus of the amygdala (CEA) is a core integrating node. The current study analyzed the activity of CEA inputs in male and female rats to determine if specific pathways are recruited during feeding under novelty. Recruitment of direct inputs from the paraventricular nucleus of the thalamus (PVT), the infralimbic cortex (ILA), the agranular insular cortex (AI), the hippocampal ventral field CA1, and the bed nucleus of the stria terminals (BST) was assessed with combined retrograde tract tracing and Fos induction analysis. The study found that during consumption of a novel food in a novel environment, larger number of neurons within the PVTp and the CA1 that send monosynaptic inputs to the CEA were recruited compared to controls that consumed familiar food in a familiar environment. The ILA, AI, and BST inputs to the CEA were similarly recruited across conditions. There were no sex differences in activation of any of the pathways analyzed. These results suggest that the PVTp-CEA and CA1-CEA pathways underlie feeding inhibition during novelty and could be potential sites of malfunction in excessive food avoidance.

The effects of acupuncture on depression by regulating BDNF-related balance via lateral habenular nucleus BDNF/TrkB/CREB signaling pathway in rats

Depression is a major mental disease worldwide, causing dysfunction of Lateral Habenular (LHb). As a non-invasive alternative, acupuncture (AP) has been widely used to treat depression in clinic, yet few basic studies have been focused on the effects and mechanism of acupuncture on synaptic plasticity in LHb. Therefore, this study aimed to explore the potential mechanism of the antidepressant effect of acupuncture. Male Sprague-Dawley (SD) rats were randomly divided into control, chronic unpredictable mild stress (CUMS), AP, fluoxetine (FLX), acupoint catgut embedding (ACE), sham-ACE groups (n = 9/group). Rats were given a 28-day treatment at the Shangxing (GV23) and Fengfu (GV16) acupoints with acupuncture, ACE, sham-ACE or fluoxetine (2.1 mg/kg). The results showed that AP, FLX and ACE suppressed the behavioral deficits, increased the level of the 5-hydroxytryptamine and FNDC5/IRISIN in serum, also reduced the expression of pro-BDNF impacted by CUMS. Both AP and FLX ameliorated the %area of IBA-1, GFAP, BrdU and DCX in the LHb and increased the expression of BDNF/TrkB/CREB, with non-significant difference between the two groups These findings suggest that AP therapy relieves depression-related manifestations in depressed rats, suggesting a potential mechanism via the BDNF/TrkB/CREB pathway in LHb.

SARS-CoV-2 S1 protein causes brain inflammation by reducing intracerebral acetylcholine production

Neurological complications that occur in SARS-CoV-2 infection, such as olfactory dysfunction, brain inflammation, malaise, and depressive symptoms, are thought to contribute to long COVID. However, in autopsies of patients who have died from COVID-19, there is normally no direct evidence that central nervous system damage is due to proliferation of SARS-CoV-2. For this reason, many aspects of the pathogenesis mechanisms of such symptoms remain unknown. Expressing SARS-CoV-2 S1 protein in the nasal cavity of mice was associated with increased apoptosis of the olfactory system and decreased intracerebral acetylcholine production. The decrease in acetylcholine production was associated with brain inflammation, malaise, depressive clinical signs, and decreased expression of the cytokine degrading factor ZFP36. Administering the cholinesterase inhibitor donepezil to the mice improved brain inflammation, malaise and depressive clinical signs. These findings could contribute to the elucidation of the pathogenesis mechanisms of neurological complications associated with COVID-19 and long COVID.

Integrated lipidomic and transcriptomic analysis reveals clarithromycin-induced alteration of glycerophospholipid metabolism in the cerebral cortex of mice

Clarithromycin (CLA) has been widely used in the treatment of bacterial infection. Research reveals the adverse effects on the central nervous system among patients receiving CLA treatment; whereas, a relevant underlying mechanism remains considerably unclear. According to our research, an integrated lipidomic and transcriptomic analysis was applied to explore the effect of CLA on neurobehavior. CLA treatment caused anxiety-like behaviors dose-dependently during open field as well as elevated plus maze trials on mice. Transcriptomes and LC/MS-MS-based metabolomes were adopted for investigating how CLA affected lipidomic profiling as well as metabolic pathway of the cerebral cortex. CLA exposure greatly disturbed glycerophospholipid metabolism and the carbon chain length of fatty acids. By using whole transcriptome sequencing, we found that CLA significantly downregulated the mRNA expression of CEPT1 and CHPT1, two key enzymes involved in the synthesis of glycerophospholipids, supporting the findings from the lipidomic profiling. Also, CLA causes changes in neuronal morphology and function in vitro, which support the existing findings concerning neurobehavior in vivo. We speculate that altered glycerophospholipid metabolism may be involved in the neurobehavioral effect of CLA. Our findings contribute to understanding the mechanisms of CLA-induced adverse effects on the central nervous system. 1. Clarithromycin treatment caused anxiety-like behavior with dose-dependent response both in the open field and elevated plus maze test in mice; 2. Clarithromycin exposing predominately disturbed the metabolism of glycerophospholipids in the cerebral cortex of mice; 3. Clarithromycin application remarkably attenuated CEPT1 and CHPT1 gene expression, which participate in the last step in the synthesis of glycerophospholipids; 4. The altered glycerophospholipid metabolomics may be involved in the abnormal neurobehavior caused by clarithromycin.

Contribution of the opioid system to depression and to the therapeutic effects of classical antidepressants and ketamine

Major depressive disorder (MDD) afflicts approximately 5 % of the world population, and about 30-50 % of patients who receive classical antidepressant medications do not achieve complete remission (treatment resistant depressive patients). Emerging evidence suggests that targeting opioid receptors mu (MOP), kappa (KOP), delta (DOP), and the nociceptin/orphanin FQ receptor (NOP) may yield effective therapeutics for stress-related psychiatric disorders. As depression and pain exhibit significant overlap in their clinical manifestations and molecular mechanisms involved, it is not a surprise that opioids, historically used to alleviate pain, emerged as promising and effective therapeutic options in the treatment of depression. The opioid signaling is dysregulated in depression and numerous preclinical studies and clinical trials strongly suggest that opioid modulation can serve as either an adjuvant or even an alternative to classical monoaminergic antidepressants. Importantly, some classical antidepressants require the opioid receptor modulation to exert their antidepressant effects. Finally, ketamine, a well-known anesthetic whose extremely efficient antidepressant effects were recently discovered, was shown to mediate its antidepressant effects via the endogenous opioid system. Thus, although opioid system modulation is a promising therapeutical venue in the treatment of depression further research is warranted to fully understand the benefits and weaknesses of such approach.

NMDA Receptor Activation-Dependent Antidepressant-Relevant Behavioral and Synaptic Actions of Ketamine

Ketamine is a well-characterized NMDA receptor (NMDAR) antagonist, although the relevance of this pharmacology to its rapid (within hours of administration) antidepressant actions, which depend on mechanisms convergent with strengthening of excitatory synapses, is unclear. Activation of synaptic NMDARs is necessary for the induction of canonical long-term potentiation (LTP) leading to a sustained expression of increased synaptic strength. We tested the hypothesis that induction of rapid antidepressant effects requires NMDAR activation, by using behavioral pharmacology, western blot quantification of hippocampal synaptoneurosomal protein levels, and ex vivo hippocampal slice electrophysiology in male mice. We found that ketamine exerts an inverted U-shaped dose-response in antidepressant-sensitive behavioral tests, suggesting that an excessive NMDAR inhibition can prevent ketamine's antidepressant effects. Ketamine's actions to induce antidepressant-like behavioral effects, up-regulation of hippocampal AMPAR subunits GluA1 and GluA2, as well as metaplasticity measured ex vivo using electrically-stimulated LTP, were abolished by pretreatment with other non-antidepressant NMDAR antagonists, including MK-801 and CPP. Similarly, the antidepressant-like actions of other putative rapid-acting antidepressant drugs (2R,6R)-hydroxynorketamine (ketamine metabolite), MRK-016 (GABAAα5 negative allosteric modulator), and LY341495 (mGlu2/3 receptor antagonist) were blocked by NMDAR inhibition. Ketamine acted synergistically with an NMDAR positive allosteric modulator to exert antidepressant-like behavioral effects and activation of the NMDAR subunit GluN2A was necessary and sufficient for such relevant effects. We conclude rapid-acting antidepressant compounds share a common downstream NMDAR-activation dependent effector mechanism, despite variation in initial pharmacological targets. Promoting NMDAR signaling or other approaches that enhance NMDAR-dependent LTP-like synaptic potentiation may be an effective antidepressant strategy.SIGNIFICANCE STATEMENT The anesthetic and antidepressant drug ketamine is well-characterized as an NMDA receptor (NMDAR) antagonist; though, the relevance and full impact of this pharmacology to its antidepressant actions is unclear. We found that NMDAR activation, which occurs downstream of their initial actions, is necessary for the beneficial effects of ketamine and several other putative antidepressant compounds. As such, promoting NMDAR signaling, or other approaches that enhance NMDAR-dependent long-term potentiation (LTP)-like synaptic potentiation in vivo may be an effective antidepressant strategy directly, or acting synergistically with other drug or interventional treatments.

Lumateperone Normalizes Pathological Levels of Acute Inflammation through Important Pathways Known to Be Involved in Mood Regulation

Lumateperone is indicated for the treatment of schizophrenia in adults and for depressive episodes associated with bipolar I or II disorder (bipolar depression) in adults, as monotherapy and as adjunctive therapy with lithium or valproate (Calabrese et al., 2021). It is currently under evaluation for the treatment of major depressive disorder (www.ClinicalTrials.gov). Lumateperone acts by selectively modulating serotonin, dopamine, and glutamate neurotransmission in the brain. However, other mechanisms could be involved in the actions of lumateperone, and because of the connection between the immune system and psychiatric health, we hypothesized that lumateperone might improve symptoms of depression, at least in part, by normalizing pathologic inflammation. Here, we show that in male and female C57BL/6 mice subjected to an acute immune challenge, lumateperone reduced aberrantly elevated levels of key proinflammatory cytokines (e.g., IL-1β, IL-6, and TNF-α) in both brain and serum; lumateperone also reduced proinflammatory cytokines in male mice under acute behavioral stress. Further, we demonstrate that lumateperone altered key genes/pathways involved in maintaining tissue integrity and supporting blood-brain barrier function, such as claudin-5 and intercellular adhesion molecule 1. In addition, in acutely stressed male Sprague Dawley rats, lumateperone conferred anxiolytic- and antianhedonic-like properties while enhancing activity in the mammalian target of rapamycin complex 1 pathway in the PFC. Together, our preclinical findings indicate that lumateperone, in addition to its ability to modulate multiple neurotransmitter systems, could also act by reducing the impact of acute inflammatory challenges.SIGNIFICANCE STATEMENT Lumateperone is indicated in adults to treat schizophrenia and depressive episodes associated with bipolar I or II disorder, as monotherapy and adjunctive therapy with lithium or valproate. Because aberrant immune system activity is associated with increased depressive symptoms, the relationship between lumateperone and immune function was studied. Here, lumateperone reduced the levels of proinflammatory cytokines that were increased following an immune challenge or stress in mice. Additionally, lumateperone altered genes and pathways that maintain blood-brain barrier integrity, restored an index of blood-brain barrier function, reduced anxiety-like behavior in rodents, and enhanced mammalian target of rapamycin complex 1 pathway signaling in the PFC. These results highlight the anti-inflammatory actions of lumateperone and describe how lumateperone may reduce immune pathophysiology, which is associated with depressive symptoms.

ERK/mTOR signaling may underlying the antidepressant actions of rapastinel in mice

Rapastinel as the allosteric modulator of N-methyl-D-aspartate receptor (NMDAR) produces rapid antidepressant-like effects dependent on brain-derived neurotrophic factor (BDNF) and VGF (nonacryonimic) release. Herein, we further explore the molecular mechanisms of the antidepressant effects of repeated administration with rapastinel in mice. Our results showed that continuous 3-day rapastinel (5 and 10 mg/kg, i.v.) produced antidepressant-like actions dependent on the increase in extracellular regulated protein kinase (ERK)/mammalian target of rapamycin (mTOR) signaling and downstream substrates p70S6 kinase (p70S6k) and the eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), which may induce the expression of VGF and BDNF in the hippocampus and prefrontal cortex of mice. Furthermore, compared with a single treatment, our data indicated that 3-day repeated rapastinel treatment produced antidepressant-like actions accompanied by potentiation of ERK/mTOR/VGF/BDNF/tropomyosin-related kinase receptor B (TrkB) signaling. Based on previous and our supplementary data that showed the pivotal role of on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) in the rapid release of VGF and BDNF and activation of TrkB by a single dose of rapastinel, we postulate that the antidepressant-like effects of single or repeated administration of rapastinel may result in the rapid release of VGF and BDNF or ERK/mTOR signaling pathway-mediated VGF/BDNF/TrkB autoregulatory feedback loop respectively. Our current work adds new knowledge to the molecular mechanisms that underlie the antidepressant-like actions of rapastinel in mice.

Reviewing the role of gut microbiota in the pathogenesis of depression and exploring new therapeutic options

The relationship between gut microbiota (GM) and mental health is one of the focuses of psychobiology research. In recent years, the microbial-gut-brain axis (MGBA) concept has gradually formed about this bidirectional communication between gut and brain. But how the GM is involved in regulating brain function and how they affect emotional disorders these mechanisms are tenuous and limited to animal research, and often controversial. Therefore, in this review, we attempt to summarize and categorize the latest advances in current research on the mechanisms of GM and depression to provide valid information for future diagnoses and therapy of mental disorders. Finally, we introduced some antidepressant regimens that can help restore gut dysbiosis, including classic antidepressants, Chinese materia medica (CMM), diet, and exogenous strains. These studies provide further insight into GM's role and potential pathways in emotion-related diseases, which holds essential possible clinical outcomes for people with depression or related psychiatric disorders. Future research should focus on clarifying the causal role of GM in disease and developing microbial targets, applying these findings to the prevention and treatment of depression.

Chronic clomipramine treatment reverses depressogenic-like effects of a chronic treatment with dexamethasone in rats

Corticosteroids are widely used in medicine, for their anti-inflammatory and immunosuppressive actions, but can lead to troubling psychiatric side-effects. In fact, corticosteroids can induce many symptoms and syndromes, for example, mood disorders, anxiety and panic disorder, suicidal thinking and behavior. Furthermore, chronic stress and the administration of exogenous glucocorticoids are reported to induce affective changes in humans and rodents that relate to depressive state. Animal models are highly useful tools for studying the depression etiology. Face validity, construct validity, and predictive validity are the main criteria to evaluate animal depression models. The present study aimed to investigate the behavioral, cognitive, and biochemical effects of a chronic administration of DEX on Wistar rats. Wistar rats were administered daily with DEX (1.5 mg/kg, i.p., 21 days) or saline, the clomipramine treatment (2 mg/kg, i.p.) was realized just after the DEX injections for 21 days. DEX induced changes were evaluated by: forced swimming, novelty suppressed feeding, saccharin preference, open field, Morris water maze, and oxidative stress state in the brain. Results showed that chronic DEX administration conduct to a range of depression-related behavioral traits, including anhedonia, despair, weight loss, anxiety-like behavior, and cognitive impairments, which fill the face validity criterion. The DEX induced behavioral changes may result from the massive production of oxidative stress agents. This sustains the etiological hypothesis claiming that hyper-circulating glucocorticoid resulting from HPA dysfunction induces damage in certain neural structures related to depressive disorder, essentially the hippocampus. The antidepressant treatment has restored the behavioral state of rats which fills the predictive validity criterion.

The bed nucleus of the stria terminalis in threat detection: task choice and rodent experience

Behavioural reactivity to potential threat is used to experimentally refine models of anxiety symptoms in rodents. We present a short review of the literature tying the most commonly used tasks to model anxiety symptoms to functional recruitment of bed nucleus of the stria terminalis circuits (BNST). Using a review of studies that investigated the role of the BNST in anxiety-like behaviour in rodents, we flag the certain challenges for the field. These stem from inconsistent methods of reporting the neuroanatomical BNST subregions and the interpretations of specific behaviour across a wide variety of tasks as 'anxiety-like'. Finally, to assist in interpretation of the findings, we discuss the potential interactions between typically used 'anxiety' tasks of innate behaviour that are potentially modulated by the social and individual experience of the animal.

Bacteriophages allow selective depletion of gut bacteria to produce a targeted-bacterium-depleted mouse model

The gut microbiome is essential for human health. Mouse microbiota models, including gnotobiotic mice, are the most prominent tools to elucidate the functions of gut bacteria. Here, we propose a targeted-bacterium-depleted (TBD) model using lytic bacteriophage to selectively deplete gut bacterium of healthy or otherwise defined mice. These phage-treated animals should have a near-complete spectrum of gut bacteria except for the depleted bacterium. To prove the concept, we employed Escherichia coli-specific phage T7 to repress E. coli in the healthy mice. Our results showed that the E. coli-depleted mice exhibited bravery-like behaviors, correlated to the presence of E. coli rather than the equilibrium among gut bacteria. Thus, we demonstrate that the TBD model is a powerful tool to elucidate the function of a specific bacterial species within a near-intact gut microbiota environment and complements gnotobiotic mice models.

Exploring the Credibility of Psilocybin-assisted Therapy and Cognitive-behavioral Therapy for Depression

Depression treatments succeed with many but leave others unimproved, and they can generate concerns about side effects, time, and cost. Psilocybin has generated media attention and empirical support for antidepressant effects, but lay impressions of its effectiveness are unclear. Although perceptions of treatment credibility contribute to outcome, beliefs about the credibility of psilocybin-assisted therapy (PAT) among potential patients remain uninvestigated, especially relative to cognitive-behavioral therapy (CBT), a common, empirically-validated approach. The present study examined credibility ratings for CBT and PAT among individuals reporting depressive symptoms. Participants (N = 803) from Amazon's MTurk platform reported demographics, depressive symptoms, and psychotherapy experience, then read data-based vignettes describing each therapy and rated their credibility. Individuals rated CBT as more credible than PAT. Those with therapy experience rated CBT as more credible than those without. Men and lifetime hallucinogen users rated PAT more credible than women and non-users, but few other predictors accounted for much variance in credibility. Results suggest that potential clients appear cautious about PAT. As continued work examines the effectiveness of psychedelic-assisted interventions, researchers and clinicians must consider patients' beliefs about treatments as potential predictors of outcomes. Additionally, the paradigm used here might have potential for examining credibility of many interventions.

The Antidepressant-like Activity, Effects on Recognition Memory Deficits, Bioavailability, and Safety after Chronic Administration of New Dual-Acting Small Compounds Targeting Neuropsychiatric Symptoms in Dementia

This study aimed to extend the body of preclinical research on prototype dual-acting compounds combining the pharmacophores relevant for inhibiting cyclic nucleotide phosphodiesterase 10 (PDE10A) and serotonin 5-HT_1A/5-HT₇ receptor (5-HT_1AR/5-HT₇R) activity into a single chemical entity (compounds PQA-AZ4 and PQA-AZ6). After i.v. administration of PQA-AZ4 and PQA-AZ6 to rats, the brain to plasma ratio was 0.9 and 8.60, respectively. After i.g. administration, the brain to plasma ratio was 5.7 and 5.3, respectively. An antidepressant-like effect was observed for PQA-AZ6 in the forced swim test, after chronic 21-day treatment via i.p. administration with 1 mg/kg/day. Both compounds revealed an increased level of brain-derived neurotrophic factor (Bdnf) mRNA in the hippocampus and prefrontal cortex. Moreover, PQA-AZ4 and PQA-AZ6 completely reversed (+)-MK801-induced memory disturbances comparable with the potent PDE10 inhibitor, compound PQ-10. In the safety profile that included measurements of plasma glucose, triglyceride, and total cholesterol concentration, liver enzyme activity, the total antioxidant activity of serum, together with weight gain, compounds exhibited no significant activity. However, the studied compounds had different effects on human normal fibroblast cells as revealed in in vitro assay. The pharmacokinetic and biochemical results support the notion that these novel dual-acting compounds might offer a promising therapeutic tool in CNS-related disorders.

Novel Antidepressant-Like Properties of the Iron Chelator Deferiprone in a Mouse Model of Depression

Depressed individuals who carry the short allele for the serotonin-transporter-linked promotor region of the gene are more vulnerable to stress and have reduced response to first-line antidepressants such as selective serotonin reuptake inhibitors. Since depression severity has been reported to correlate with brain iron levels, the present study aimed to characterise the potential antidepressant properties of the iron chelator deferiprone. Using the serotonin transporter knock-out (5-HTT KO) mouse model, we assessed the behavioural effects of acute deferiprone on the Porsolt swim test (PST) and novelty-suppressed feeding test (NSFT). Brain and blood iron levels were also measured following acute deferiprone. To determine the relevant brain regions activated by deferiprone, we then measured c-Fos expression and applied network-based analyses. We found that deferiprone reduced immobility time in the PST in 5-HTT KO mice and reduced latency to feed in the NSFT in both genotypes, suggesting potential antidepressant-like effects. There was no effect on brain or blood iron levels following deferiprone treatment, potentially indicating an acute iron-independent mechanism. Deferiprone reversed the increase in c-Fos expression induced by swim stress in 5-HTT KO mice in the lateral amygdala. Functional network analyses suggest that hub regions of activity in mice treated with deferiprone include the caudate putamen and prefrontal cortex. The PST-induced increase in network modularity in wild-type mice was not observed in 5-HTT KO mice. Altogether, our data show that the antidepressant-like effects of deferiprone could be acting via an iron-independent mechanism and that these therapeutic effects are underpinned by changes in neuronal activity in the lateral amygdala.

Morinda officinalis oligosaccharides mitigate chronic mild stress-induced inflammation and depression-like behaviour by deactivating the MyD88/PI3K pathway via E2F2

Morinda officinalis oligosaccharides (MOs) are natural herbal extracts that have been shown to exert antidepressant effects. However, the mechanism of this effect remains unclear. Here, we explored the mechanism by which MOs improved experimental depression. Using a chronic mild stress (CMS) murine model, we examined whether MOs could protect against depressive-like behaviour. Lipopolysaccharide (LPS)- and ATP-treated BV2 cells were used to examine the potential mechanism by which MOs mediate the inflammatory response. We found that MOs prevented the CMS-induced reduction in the sucrose preference ratio in the sucrose preference test (SPT) and shortened the immobility durations in both the tail suspension test (TST) and forced swim test (FST). We also noticed that MOs suppressed inflammatory effects by deactivating the MyD88/PI3K pathway via E2F2 in CMS mice or LPS- and ATP-stimulated BV2 cells. Furthermore, overexpression of E2F2 blunted the beneficial effects of MOs in vitro. Collectively, these data showed that MOs exerted antidepressant effects in CMS mice by targeting E2F2-mediated MyD88/PI3K signalling pathway.

Trihexyphenidyl increases delta activity in non-rapid eye movement sleep without impairing cognitive function in rodent models

Both human and rodent studies suggest the link between non-rapid eye movement (NREM) sleep and cognition. Recent study indicated that selective activation of cholinergic neurons in basal forebrain inhibits electroencephalogram (EEG) delta power and shortens NREM sleep. In the current study, we aimed to test the pharmacological effect of trihexyphenidyl (THP), a selective muscarinic M1 receptor antagonist, on EEG power spectra and sleep with or without the selective activation of basal forebrain cholinergic neurons. THP (1, 2, and 3 mg/kg) was administrated intraperitoneally in natural sleep phase. Basal forebrain cholinergic neurons expressing modified G protein-coupled muscarinic receptors (hM3Dq) were activated by intraperitoneal injection of clozapine-N-oxide in ChAT-IRES-Cre mice. EEG and electromyogram (EMG) signals were recorded in freely moving mice to analyze EEG power spectrum and sleep hypnogram. Y-maze and novel object recognition tests were used for testing cognition. THP 1 mg/kg significantly increased EEG delta power and facilitated NREM sleep in wildtype mice, while THP 3 mg/kg was required in ChAT-IRES-Cre mice treated with clozapine-N-oxide. THP with dosage up to 8 mg/kg did not induce cognitive impairments in wildtype mice. EEG delta power of NREM sleep is often used as an indicator of sleep depth or sleep quality, which tightly link with sleep-dependent cognition. Taken together, the data collected from rodents hinted that, THP could possibly be used as the NREM sleep facilitator in humans.

Encore: Behavioural animal models of stress, depression and mood disorders

Animal studies over the past two decades have led to extensive advances in our understanding of pathogenesis of depressive and mood disorders. Among these, rodent behavioural models proved to be of highest informative value. Here, we present a comprehensive overview of the most popular behavioural models with respect to physiological, circuit, and molecular biological correlates. Behavioural stress paradigms and behavioural tests are assessed in terms of outcomes, strengths, weaknesses, and translational value, especially in the domain of pharmacological studies.