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The Hypothalmic-Pituitary-Adrenal axis also known as the HPA axis is central to stress response. It also acts as the relay center between the body and the brain. We analysed hypothalamic proteome from mice subjected to chronic social defeat paradigm using iTRAQ based quantitative proteomics to identify changes associated with stress response. We identified greater than 2000 proteins after processing our samples analysed through Q-Exactive (Thermo) and Orbitrap Velos (Thermo) at 5% FDR. Analysis of data procured from the runs showed that the proteins whose levels were affected belonged primarily to mitochondrial and metabolic processes, translation, complement pathway among others. We also found increased levels of fibrinogen, myelin basic protein (MBP) and neurofilaments (NEFL, NEFM, NEFH) in the hypothalamus from socially defeated mice. Interestingly, research indicates that these proteins are upregulated in blood and CSF of subjects exposed to trauma and stress. Since hypothalamus secreted proteins can be found in blood and CSF, their utility as biomarkers in depression holds an impressive probability and should be validated in clinical samples. [ABSTRACT FROM AUTHOR]

• Chronic social defeat stress increases ghsr mRNA expression in the VTA in male mice. • GHSR signaling in the VTA is required for stress-induced changes in caloric intake in male mice. • Inhibition of GHSR signaling in the VTA of male mice exacerbates anxiogenic effects of chronic stress. Ghrelin, a hormone secreted by the stomach, binds to the growth hormone secretagogue receptor (GHSR) in various brain regions to produce a number of behavioral effects that include increased feeding motivation. During social defeat stress, ghrelin levels rise in correlation with increased feeding and potentially play a role in attenuating the anxiogenic effects of social defeat. One region implicated in the feeding effects of ghrelin is the ventral tegmental area (VTA), a region implicated in reward seeking behaviors, and linked to social defeat in mice. Here we examined the role of GHSR signaling in the VTA in feeding behavior in mice exposed to social defeat stress. Male C57BL/J6 mice that were socially defeated once daily for 3 weeks ate more, had higher plasma ghrelin level and increased GHSR expression in the VTA compared to non-stressed mice. Socially defeated GHSR KO mice failed to increase their caloric intake in response to this stressor but rescue of GHSR expression in the VTA restored feeding responses. Finally, we pharmacologically blocked VTA GHSR signalling with JMV2959 infused via an indwelling VTA cannula connected to a minipump. Vehicle-treated mice increased their caloric intake during social defeat, but JMV2959-infusions attenuated feeding responses and increased anxiety-like behaviors. The data suggest that GHSR signalling in the VTA is critical for the increases in appetite observed during chronic social defeat stress. Furthermore, these data support the idea that GHSR signaling in the VTA may also have anxiolytic effects, and blocking GHSR in this region may result in an anxiety-like phenotype. [ABSTRACT FROM AUTHOR]

Anxiety disorders are prevalent mental disorders. Their predisposition involves a combination of genetic and environmental risk factors, such as psychosocial stress. Myelin plasticity was recently associated with chronic stress in several mouse models. Furthermore, we found that changes in both myelin thickness and node of Ranvier morphology after chronic social defeat stress are influenced by the genetic background of the mouse strain. To understand cellular and molecular effects of stress‐associated myelin plasticity, we established an oligodendrocyte (OL) model consisting of OL primary cell cultures isolated from the C57BL/6NCrl (B6; innately non‐anxious and mostly stress‐resilient strain) and DBA/2NCrl (D2; innately anxious and mostly stress‐susceptible strain) mice. Characterization of naïve cells revealed that D2 cultures contained more pre‐myelinating and mature OLs compared with B6 cultures. However, B6 cultures contained more proliferating oligodendrocyte progenitor cells (OPCs) than D2 cultures. Acute exposure to corticosterone, the major stress hormone in mice, reduced OPC proliferation and increased OL maturation and myelin production in D2 cultures compared with vehicle treatment, whereas only OL maturation was reduced in B6 cultures. In contrast, prolonged exposure to the synthetic glucocorticoid dexamethasone reduced OPC proliferation in both D2 and B6 cultures, but only D2 cultures displayed a reduction in OPC differentiation and myelin production. Taken together, our results reveal that genetic factors influence OL sensitivity to glucocorticoids, and this effect is dependent on the cellular maturation stage. Our model provides a novel framework for the identification of cellular and molecular mechanisms underlying stress‐associated myelin plasticity. [ABSTRACT FROM AUTHOR]

As recently as the late 20th century, Schizophrenia, a category of mental illness with widely varying phenotypic symptoms, was believed by psychobiologists to be a genetically based disorder in which the environment played a limited etiological role. Yet a growing body of evidence indicates a strong correlation between schizophrenia and environmental factors. This theoretical paper explores the relationship between highly elevated rates of schizophrenia in some low-income minority communities worldwide and trauma-related dissociative symptoms that often mimic schizophrenia. Elevated rates of schizophrenia in racially and ethnically isolated, inner-city Black populations are well documented. This paper contains evidence proposing that this amplification in the rate of schizophrenia is mediated by childhood trauma, disorganized attachment, and social defeat. Further, evidence demonstrating how these three variables combine in early childhood to incubate dissociative disorders will also be conveyed. The misdiagnosis of dissociative disorders as schizophrenia is theorized to partially mediate the increased rate of schizophrenia in communities that experience high levels of racial/ethnic discrimination. It is argued that this misdiagnosis is often attributable to cultural misunderstanding and/or a lack of knowledge about dissociative disorders [ABSTRACT FROM AUTHOR]

Adolescence is a period characterized by a high vulnerability to emotional disorders, which are modulated by biological, psychological, and social factors. However, the underlying mechanisms remain poorly understood. Combining physical or emotional social defeat stress (PS and ES) and pair or isolation rearing conditions, we investigated the effects of stress type and social support on emotional behavior and central immune molecules in adolescent mice, including anxiety, social fear, and social interaction strategies, as well as changes in microglia-specific molecules (ionized calcium-binding adaptor molecule 1 (Iba1) and a cluster of differentiation molecule 11b (CD11b)) in the medial prefrontal cortex (mPFC), hippocampus (HIP), amygdala (AMY), and nucleus accumbens (NAc). Mice exposed to both physical stress and isolated rearing condition exhibited the highest levels of anxiety, social fear, and microglial CD11b expression in the NAc. In terms of social support, pair-housing with siblings ameliorated social fear and NAc molecular changes in ES mice, but not in PS mice. The reason for the differential benefit from social support was attributed to the fact that ES mice exhibited more active and less passive social strategies in social environment compared to PS mice. Further, the levels of stress-induced social fear were positively associated with the expression of microglial CD11b in the NAc. These findings offer extensive evidence regarding the intricate effects of multiple social factors on social anxiety and immune alteration in the NAc of adolescent mice. Additionally, they suggest potential behavioral and immune intervention strategies for anxiety-related disorders in adolescents. • Stress type and social support displayed distinct effects on anxiety and NAc microglial CD11b of adolescent mice. • Stress-induced social fear was positively associated with the expression of microglial CD11b in the NAc. • Pair-housing with siblings ameliorated social fear and NAc molecular changes in emotionally but not physically stressed mice. • Different benefit from social support was attributed to more active and less passive social strategies in ES than PS mice. • NAc microglial activities and social strategies are involved in effects of social factors on anxiety in adolescents. [ABSTRACT FROM AUTHOR]

[Display omitted] • HMGB1/STAT3/p65 axis mediated microglial activation and autophagy in mPFC correlated with MDD were first identified, and HMGB1 was found to be a potential biomarker for MDD. • Increased HMGB1 expression was mainly observed in microglia from the medial prefrontal cortex of MDD model mice. • Specific knockdown of HMGB1 rescues chronic stress-induced depressive-related phenotypes, microglial activation, and autophagy in mice. • The effects induced by chronic stress were mimicked by exogenous administration of recombinant HMGB1 or specific overexpression of HMGB1, while blocked by STAT3 specific inhibitor or p65 knockdown. • Inhibition of HMGB1/STAT3/p65 axis prevented LPS-induced microglial activation and autophagy in vitro , which was reversed by recombinant HMGB1 protein overexpression. • Microglial HMGB1/STAT3/p65 axis within the mPFC is a novel therapeutic target in the treatment of MDD associated with stress. Neuroinflammation and autophagy are implicated in stress-related major depressive disorder (MDD), but the underlying molecular mechanisms remain largely unknown. 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. 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. 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. Our study established the role of microglial HMGB1/STAT3/p65 axis in mPFC in mediating microglial activation and autophagy in MDD. [ABSTRACT FROM AUTHOR]

Depression is associated with pathological changes and metabolic abnormalities in multiple brain regions. The simultaneous comprehensive and in situ detection of endogenous molecules in all brain regions is essential for a comprehensive understanding of depression pathology, which is described in this paper. A method based on desorption electrospray ionization mass spectrometry imaging (DESI-MSI) technology was developed to classify mouse brain regions using characteristic lipid molecules and to detect the metabolites in mouse brain tissue samples simultaneously. The results showed that characteristic lipid molecules can be used to clearly distinguish each subdivision of the mouse brain, and the accuracy of this method is higher than that of the conventional staining method. The cerebellar cortex, medial prefrontal cortex, hippocampus, striatum, nucleus accumbens-core, and nucleus accumbens-shell exhibited the most significant differences in the chronic social defeat stress model. An analysis of metabolic pathways revealed that 13 kinds of molecules related to energy metabolism and purine metabolism exhibited significant changes. A DESI-MSI method was developed for the detection of pathological brain sections. We found, for the first time, that there are characteristic changes in the energy metabolism in the cortex and purine metabolism in the striatum, which is highly important for obtaining a deeper and more comprehensive understanding of the pathology of depression and discovering regulatory targets. [ABSTRACT FROM AUTHOR]

Stress-induced illnesses, like major depression, are among the leading causes of disability across the world. Consequently, there is a dire need for the validation of translationally-suited animal models incorporating social stress to uncover the etiology of depression. Prairie voles (Microtus ochrogaster) are more translationally relevant than many other rodent models as they display monogamous social and bi-parental behaviors. Therefore, we evaluated whether a novel social defeat stress (SDS) model in male prairie voles induces depression-relevant behavioral outcomes. Adult sexually-naïve male prairie voles experienced SDS bouts from a conspecific pair-bonded male aggressor, 10 min per day for 10 consecutive days. Non-stressed controls (same-sex siblings) were housed in similar conditions but never experienced physical stress. Twenty-four h later, voles were evaluated in social interaction, sucrose preference, and Morris water maze tests – behavioral endpoints validated to assess social withdrawal, anhedonia-related behavior, and spatial memory performance, respectively. SDS-exposed voles displayed lower sociability and body weight, decreased preference for a sucrose solution, and impairment of spatial memory retrieval. Importantly, no differences in general locomotor activity were observed as a function of SDS exposure. This study does not include female voles in the experimental design. We found that repeated SDS exposure, in male prairie voles, results in a depression-relevant phenotype resembling an anhedonia-like outcome (per reductions in sucrose preference) along with social withdrawal and spatial memory impairment – highlighting that the prairie vole is a valuable model with potential to study the neurobiology of social stress-induced depression-related outcomes. • Social defeat stress decreases social behavior in adult male prairie voles • Social defeat stress decreases sucrose preference in adult male prairie voles • Social defeat stress impairs spatial memory in adult male prairie voles • Vole social defeat stress displays strong face validity as a model for the study of depression-related phenotypes [ABSTRACT FROM AUTHOR]

Social status in humans, generally reflected by socioeconomic status, has been associated, when constrained, with heightened vulnerability to pathologies including psychiatric diseases. Social hierarchy in mice translates into individual and interdependent behavioral strategies of animals within a group. The rules leading to the emergence of a social organization are elusive, and detangling the contribution of social status from other factors, whether environmental or genetic, to normal and pathological behaviors remains challenging. We investigated the mechanisms shaping the emergence of a social hierarchy in isogenic C57BL/6 mice raised in groups of 4 using conditional mutant mouse models and chemogenetic manipulation of dopamine midbrain neuronal activity. We further studied the evolution of behavioral traits and the vulnerability to psychopathological-like phenotypes according to the social status of the animals. Higher sociability predetermined higher social hierarchy in the colony. Upon hierarchy establishment, higher-ranked mice showed increased anxiety and better cognitive abilities in a working memory task. Strikingly, the higher-ranked mice displayed a reduced activity of dopaminergic neurons within the ventral tegmental area, paired with a decreased behavioral response to cocaine and a decreased vulnerability to depressive-like behaviors following repeated social defeats. The pharmacogenetic inhibition of this neuronal population and the genetic inactivation of glucocorticoid receptor signaling in dopamine-sensing brain areas that resulted in decreased dopaminergic activity promoted accession to higher social ranks. Dopamine activity and its modulation by the stress response shapes social organization in mice, potentially linking interindividual and social status differences in vulnerability to psychopathologies. [ABSTRACT FROM AUTHOR]

Hyperactivity of granule cells in the ventral dentate gyrus (vDG) promotes vulnerability to chronic stress. However, which receptors in the vDG could be targeted to inhibit this hyperactivity and confer stress resilience is not known. The serotonin 1A receptor (5-HT 1A R) is a G i protein–coupled inhibitory receptor that has been implicated in stress adaptation, anxiety, depression, and antidepressant responses. 5-HT 1A Rs are highly expressed in the DG, but their potential to promote stress resilience by regulating granule cell activity has never been examined. We exposed male and female mice expressing 5-HT 1A Rs only in DG granule cells to 10 days of chronic social defeat stress (CSDS) and treated them with the 5-HT 1A R agonist 8-OH-DPAT every day 30 minutes before each defeat throughout the CSDS paradigm. We then used whole-cell current clamp recordings, immunohistochemistry for the immediate early gene cFos, corticosterone immunoassays, and behavioral testing to determine how activating 5-HT 1A Rs on granule cells affects DG activity, neuroendocrine stress responses, and avoidance behavior. We found that activating 5-HT 1A Rs hyperpolarized DG granule cells and reduced cFos+ granule cells in the vDG following CSDS, indicating that 5-HT 1A R activation rescued stress-induced vDG hyperactivity. Moreover, 5-HT 1A R activation dampened corticosterone responses to CSDS and prevented the development of stress-induced avoidance in the social interaction test and in the open field test. Our findings show that activating 5-HT 1A Rs on DG granule cells can prevent stress-induced neuronal hyperactivity of the vDG and confer resilience to chronic stress. [ABSTRACT FROM AUTHOR]

Microglial polarization and associated inflammatory activity are the key mediators of depression pathogenesis. The natural Smilax glabra rhizomilax derivative engeletin has been reported to exhibit robust anti‐inflammatory activity, but no studies to date have examined the mechanisms through which it can treat depressive symptoms. We showed that treatment for 21 days with engeletin significantly alleviated depressive‐like behaviours in chronic stress social defeat stress (CSDS) model mice. T1‐weighted imaging (T1WI), T2‐weighted imaging (T2WI) imaging revealed no significant differences between groups, but the bilateral prefrontal cortex of CSDS mice exhibited significant increases in apparent diffusion coefficient and T2 values relative to normal control mice, with a corresponding reduction in fractional anisotropy, while engeletin reversed all of these changes. CSDS resulted in higher levels of IL‐1β, IL‐6, and TNF‐a production, enhanced microglial activation, and greater M1 polarization with a concomitant decrease in M2 polarization in the mPFC, whereas engeletin treatment effectively abrogated these CSDS‐related pathological changes. Engeletin was further found to suppress the LCN2/C‐X‐C motif chemokine ligand 10 (CXCL10) signalling axis such that adeno‐associated virus‐induced LCN2 overexpression ablated the antidepressant effects of engeletin and reversed its beneficial effects on the M1/M2 polarization of microglia. In conclusion, engeletin can alleviate CSDS‐induced depressive‐like behaviours by regulating the LCN2/CXCL10 pathway and thereby altering the polarization of microglia. These data suggest that the antidepressant effects of engeletin are correlated with the polarization of microglia, highlighting a potential avenue for future design of antidepressant strategies that specifically target the microglia. [ABSTRACT FROM AUTHOR]

Rationale: Emerging evidence indicates that persistent alcohol consumption escalates psychosocial trauma achieved by social defeat stress (SDS)-induced neurobiological changes and behavioral outcomes. Treatment with compounds with neuroprotective functions is believed to reverse ethanol (EtOH)-aggravated SDS-induced behavioral impairments. Objectives: We investigated the outcomes of diosgenin treatment, a phytosteroidal sapogenin in mice co-exposed to repeated SDS and EtOH administration. Methods: During a period of 14 days, SDS male mice were repeatedly administered EtOH (20%, 10 mL/kg) orally from days 8–14 (n = 9). Within days 1–14, SDS mice fed with EtOH were simultaneously treated with diosgenin (25 and 50 mg/kg) or fluoxetine (10 mg/kg) by oral gavage. Locomotor, cognitive-, depressive-, and anxiety-like behaviors were assessed. Adrenal weight, serum glucose, and corticosterone levels were assayed. Brain markers of oxido-inflammatory, neurochemical levels, monoamine oxidase-B, and acetylcholinesterase activities were measured in the striatum, prefrontal cortex, and hippocampus. Results: The anxiety-like behavior, depression, low stress resilience, social, and spatial/non-spatial memory decline exhibited by SDS mice exposed to repeated EtOH administration were alleviated by diosgenin (25 and 50 mg/kg) and fluoxetine, illustrated by increased dopamine and serotonin concentrations and reduced monoamine oxidase-B and acetylcholinesterase activities in the prefrontal cortex, hippocampus, and striatum. Diosgenin attenuated SDS + EtOH interaction induced corticosterone release and adrenal hypertrophy, accompanied by reduced TNF-α, IL-6, malondialdehyde, and nitrite levels in the striatum, prefrontal cortex, and hippocampus. Diosgenin increased glutathione, superoxide dismutase, and catalase levels in SDS + EtOH-exposed mice. Conclusions: Our data suggest that diosgenin reverses SDS + EtOH interaction-induced behavioral changes via normalization of hypothalamic–pituitary–adrenal axis, neurochemical neurotransmissions, and inhibition of oxidative and inflammatory mediators in mice brains. [ABSTRACT FROM AUTHOR]

Emotional disorders, such as anxiety and depression, represent a major societal problem; however, the underlying neurological mechanism remains unknown. The ventral lateral septum (LSv) is implicated in regulating processes related to mood and motivation. In this study, we found that LSv GABAergic neurons were significantly activated in mice experiencing chronic social defeat stress (CSDS) after exposure to a social stressor. We then controlled LSv GABAergic neuron activity using a chemogenetic approach. The results showed that although manipulation of LSv GABAergic neurons had little effect on anxietylike behavioral performances, the activation of LSv GABAergic neurons during CSDS worsened social anxiety during a social interaction (SI) test. Moreover, LSv GABAergic neurons showed strong projections to the paraventricular nucleus (PVN) of the hypothalamus, which is a central hub for stress reactions. Remarkably, while activation of GABAergic LSv-PVN projections induced social anxiety under basal conditions, activation of this pathway during CSDS alleviated social anxiety during the SI test. On the other hand, the chemogenetic manipulation of LSv GABAergic neurons or LSvGABA-PVN projections had no significant effect on despair-like behavioral performance in the tail suspension test. Overall, LS GABAergic neurons, particularly the LSv GABAergic-PVN circuit, has a regulatory role in pathological anxiety and is thus a potential therapeutic target for the treatment of emotional disorders. [ABSTRACT FROM AUTHOR]

Social defeat stress is associated with endoplasmic reticulum (ER) stress, inflammation and apoptosis. ER stress is thought to contribute to many lifestyle diseases such as liver injury, cardiovascular dysfunction and depression. We investigated the expression of the ER stress markers RNA-dependent protein kinase-like ER kinase (PERK), eukaryotic translation initiation factor 2α (eIF2α) and C/EBP homologous protein (CHOP), as well as inflammatory and apoptotic factors, to assess how social defeat stress induces liver injury. Furthermore, we evaluated the effects of the ER stress inhibitor phenylbutyric acid (PBA) and ER stress inducer thapsigargin (TG) on liver injury. Adult mice were divided into the control, social defeat, social defeat + PBA, TG, PBA and TG + PBA groups. The social defeat and social defeat + PBA groups were simultaneously exposed to social defeat stress for 10 days. The social defeat + PBA, TG, PBA and TG + PBA groups were treated with PBA or TG via intraperitoneal injections. PBA was injected 1 h before the TG injection into the TG + PBA group. Liver samples from six groups of mice were analyzed by histological analysis and western blotting. Social defeat stress promoted ER stress, increased the expression of inflammatory factors and induced apoptosis in the liver of socially defeated mice, which was reversed by PBA. Moreover, ER stress induces TG-induced liver injury by initiating ER stress. Social defeat stress initiates ER stress, promotes the expression of inflammatory and apoptotic factors, and induces liver injury. PBA suppresses liver injury caused by social defeat stress and TG treatment. [ABSTRACT FROM AUTHOR]

The endocannabinoid system plays a crucial role in regulating mood, but the specific involvement of cannabinoid receptor type 2 (CB2R) in depression remains poorly understood. Similarly, the mechanisms by which electroacupuncture (EA) provides therapeutic benefits for depression are not clearly defined. This research aims to explore the function of CB2R in depression and examine if the therapeutic effects of EA are associated with the hippocampal CB2R system. Mice experiencing social defeat stress (SDS) were used to model depression and anxiety behaviors. We quantified hippocampal CB2R and N-arachidonoylethanolamide (AEA) levels. The efficacy of a CB2R agonist, JWH133, in mitigating SDS-induced behaviors was evaluated. Additionally, EA's impact on CB2R and AEA was assessed, along with the influence of CB2R antagonist AM630 on EA's antidepressant effects. SDS led to depressive and anxiety-like behaviors, with corresponding decreases in hippocampal CB2R and AEA. Treatment with JWH133 ameliorated these behaviors. EA treatment resulted in increased CB2R and AEA levels, while AM630 blocked these antidepressant effects. The study mainly focused on the SDS model, which may not entirely reflect other depression models. Besides, further investigation is needed to understand the precise mechanisms by which CB2R and AEA contribute to EA's effects. The study suggests hippocampal downregulation of CB2R and AEA contributes to depression. Upregulation of CB2R and AEA in response to EA suggests their involvement in EA's antidepressant effects. These findings provide insights into the role of the hippocampal CB2R system in depression and the potential mechanisms underlying EA's therapeutic effects. • SDS led to depressive and anxiety-like behaviors and downregulated CB2R and AEA expression in the hippocampus of mice. • Treatment with a CB2R agonist, JWH133, alleviated SDS-induced depressive and anxiety-like behaviors. • EA resulted in an upregulation of CB2R and AEA expression in the hippocampus and alleviated behavior defects in mice. • The CB2R antagonist AM630 hindered the antidepressant effects of EA, supporting the role of CB2R in the effects of EA. [ABSTRACT FROM AUTHOR]

LHPP was recently shown to be a risk gene for major depressive disorder. LHPP has been proven to dephosphorylate the residues of histidine, serine, threonine, and tyrosine. However, much remains unknown about how LHPP contributes to depression. In the current study, we addressed this issue by integrating approaches of genetics, molecular biology, behavioral testing, and electrophysiology. We found that levels of LHPP were upregulated in glutamatergic neurons of the ventral hippocampus in mice that displayed stress-induced depression-like behaviors. Knockout of LHPP in glutamatergic neurons of the brain improved the spontaneous activity of LHPP flox/flox·CaMKIIαCre+ (conditional knockout) mice. Adeno-associated virus–mediated LHPP knockdown in the ventral hippocampus enhanced resistance against chronic social defeat stress in mice. Manipulations of LHPP levels impacted the density of dendritic spines and excitability of CA1 pyramidal neurons by mediating the expressions of BDNF (brain-derived neurotrophic factor) and PSD95 via the modulation of the dephosphorylation of CaMKIIα and ERK. Notably, compared with wild-type LHPP , human mutant LHPP (E56K, S57L) significantly increased the activity of the CaMKIIα/ERK-BDNF/PSD95 signaling pathway. Finally, esketamine, not fluoxetine, markedly alleviated the LHPP upregulation–induced depression-like behaviors. These findings provide evidence that LHPP contributes to the pathogenesis of depression via threonine and serine hydrolases, thereby identifying LHPP as a potential therapeutic target in treating patients with major depressive disorder. [ABSTRACT FROM AUTHOR]

Over the last 20 years, the importance of 'the social' has again become a crucial theme within psychiatric research, as evidenced for example by the recent focus on the social determinants of mental health. However, what is less clear is what is meant, in this kind of research, by the very idea of the social—and what consequences those ideas have. The key purpose of the article is therefore to discuss what is often meant by the concept of 'the social'; what different ideas of the social do; and what can be at stake in the different, explicit and implicit, understandings of social life that proliferate in contemporary psychiatric research. We propose that there are, roughly, three widespread styles of social thought, wherein (a) the social is seen as structural, (b) the social is seen as individual, and (c) the social is seen as relational/processual. We exemplify these by discussing examples of 'social defeat' and 'therapeutic communities', focused on what might be at stake in different understandings of social life. Lastly, we draw on the philosopher Ludwig Wittgenstein to argue that a singular understanding of 'the social' is not achievable. [ABSTRACT FROM AUTHOR]

Experimental animal models are considered an important scientific tool used to understand the pathogenesis of depression and the mechanism of anti-depressant agents. Human depression is a unique and complex process of multifactorial etiologies. The research-based evidence suggested that a functional deficiency of norepinephrine (NE), 5-hydroxy tryptamine (5-HT), and other neurotransmitters result in depression. A mood alteration disease associated with neurotransmitter dysfunction or psychological stress. There are numerous experimental animal models available to screen antidepressant drugs, but their precise pathophysiology is not entirely wellknown. The present review focused on depression assay studies that used a variety of experimental models, including acute stress models such as the forced swim test, models of prolonged physical or social stress such as social defeat, genetic models of secondary depression, and other experiments meant to clarify the mechanisms of antidepressant medications. [ABSTRACT FROM AUTHOR]

Traumatic stress, particularly during critical developmental periods such as adolescence, has been strongly linked to an increased propensity and severity of aggression. Existing literature underscores that being a victim of abuse can exacerbate aggressive behaviors, with the amygdala playing a pivotal role in mediating these effects. Historically, animal models have demonstrated that traumatic stressors can increase attack behavior, implicating various amygdala nuclei. Building on this foundation, our previous work has highlighted how traumatic stress invokes long-lasting aggression via an excitatory pathway within the posterior ventral medial amygdala (MeApv). In the current study, we sought to further delineate this mechanism by examining the effects of acute social defeat during adolescence on aggressive behaviors and neural activation in mice. Using a common social defeat paradigm, we first established that acute social defeat during late adolescence indeed promotes long-lasting aggression, measured as attack behavior 7 days after the defeat session. Immunolabeling with c-Fos demonstrated that acute social defeat activates the MeApv and ventrolateral aspect of the ventromedial hypothalamus (VmHvl), consistent with our previous studies that used foot shock as an acute stressor. Finally, chemogenetically inhibiting excitatory MeApv neurons during social defeat significantly mitigated the aggression increase without affecting non-aggressive social behavior. These results strongly suggest that the MeApv plays a critical role in the onset of aggression following traumatic social experience, and offer the MeA as a potential target for therapeutic interventions.

There is a gap in existing knowledge of stress-triggered neurochemical and behavioral adaptations in females. This study was designed to explore the short-term consequences of a single social defeat (SD) on accumbal dopamine (DA) dynamics and related behaviors in female Wistar rats. During the SD procedure, rats demonstrated different stress-handling strategies, which were defined as active and passive coping. The “active” subjects expressed a significantly higher level of activity directed toward handling stress experience, while the “passive” ones showed an escalated freezing pattern. Remarkably, these opposite behavioral manifestations were negatively correlated. Twenty-four hours following the SD exposure, decreased immobility latency in the Porsolt test and cognitive augmentation in the new object recognition evaluation were evident, along with an increase in electrically evoked mesolimbic DA release in passive coping rats. Rats exhibiting an active pattern of responses showed insignificant changes in immobility and cognitive performance as well as in evoked mesolimbic DA response. Furthermore, the dynamics of the decline and recovery of DA efflux under the depletion protocol were significantly altered in the passive but not active female rats. Taken together, these data suggest that female rats with a passive coping strategy are more susceptible to developing behavioral and neurochemical alterations within 24 h after stress exposure. This observation may represent both maladaptive and protective responses of an organism on a short timescale.

[Display omitted] • Repeated social defeat stress model is ideal to investigate preventive and therapeutic measures for depressive-like behavior. • Partnership intervention prevents depressive-like behavior induced by repeated social defeat stress. • Single dose of 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl) benzamide treatment alleviates social avoidance behavior. Persistent stress increases the probability for developing depression significantly thereafter. Repeated social defeat stress is a widely used model to investigate depressive-like behavior in preclinical models. Hence, the repeated social defeat stress model provided an ideal animal model, through which the hypotheses of prevention and treatment can be investigated. We have successfully induced depressive-like behavior for male C57BL/6J mice with this model. Here, we reported that certain level of during-stress social interactions with single female or multiple male peer(s) exerted a positive role in preventing the development of depressive-like behavior induced by repeated social defeat stress. Our data suggested that the stress-susceptible mice may benefit from positive social interaction, which reduces the chance for depressive-like behavior development. Since numerous studies indicate that the metabotropic glutamate receptor 5 (mGluR5) plays an important role in various cognitive functions, we further investigate the treatment effect of 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl) benzamide (CDPPB) on the depressive-like behavior induced by repeated social defeat stress. Most importantly, robust anti-depressant effects have been achieved through modulating the mGluR5 function. We found that single oral dose administration of CDPPB (20 mg/kg), to some extent, alleviated the social avoidance behaviors for the stress-susceptible mice. Our data implies that the CDPPB, a positive allosteric modulator of mGluR5, is a promising anti-depressant candidate with limited side effect. [ABSTRACT FROM AUTHOR]

Violence exposure is associated with worsening anxiety and depression symptoms among adolescents. Mechanistically, social defeat stress models in mice indicate that violence increases peripherally derived macrophages in threat appraisal regions of the brain, which have been causally linked to anxious behavior. In the present study, we investigate if there is a path connecting violence exposure with internalizing symptom severity through peripheral inflammation and amygdala connectivity. Two hundred and thirty‐three adolescents, ages 12–15, from the Chicago area completed clinical assessments, immune assays and neuroimaging. A high‐dimensional multimodal mediation model was fit, using violence exposure as the predictor, 12 immune variables as the first set of mediators and 288 amygdala connectivity variables as the second set, and internalizing symptoms as the primary outcome measure. 56.2% of the sample had been exposed to violence in their lifetime. Amygdala–hippocampus connectivity mediated the association between violence exposure and internalizing symptoms (ζ̂Hippπ̂Hipp=0.059$$ {\hat{\zeta}}_{\mathrm{Hipp}}{\hat{\pi}}_{\mathrm{Hipp}}=0.059 $$, 95%CIboot=0.009,0.134$$ 95\%{\mathrm{CI}}_{\mathrm{boot}}=\left[\mathrm{0.009,0.134}\right] $$). There was no evidence that inflammation or inflammation and amygdala connectivity in tandem mediated the association. Considering the amygdala and the hippocampus work together to encode, consolidate, and retrieve contextual fear memories, violence exposure may be associated with greater connectivity between the amygdala and the hippocampus because it could be adaptive for the amygdala and the hippocampus to be in greater communication following violence exposure to facilitate evaluation of contextual threat cues. Therefore, chronic elevations of amygdala–hippocampal connectivity may indicate persistent vigilance that leads to internalizing symptoms. [ABSTRACT FROM AUTHOR]

Background: Patients undergoing surgical anesthesia increasingly suffer from preoperative depression. Clinical studies have shown that depression is a risk factor for perioperative neurocognitive disorders (PNDs) in elder patients. However, the underlying mechanism, especially at the neural circuit level, remains poorly understood. Methods: Right carotid artery separation under sevoflurane and chronic social defeat stress (CSDS) in adult mice were used to establish surgical anesthesia and chronic depression models. Cognitive function was assessed by the Y maze and novel object recognition tests. A chemogenetic approach was used to modulate the locus coeruleus‐dorsal hippocampal CA1 (LC‐dCA1) circuit. Hippocampal synaptic alterations were evaluated by Golgi staining and whole‐cell patch clamp recording. Results: We found that CSDS induced synaptic impairments in dorsal hippocampal CA1 pyramidal neurons and cognitive deficits in adult mice after surgery under sevoflurane. Chemogenetic activation of the LC‐dCA1 pathway significantly alleviated the CSDS‐induced synaptic impairments and cognitive dysfunction. On the contrary, inhibition of this pathway could mimic CSDS‐induced deficits. Furthermore, we showed that dopamine played an important role in CSDS‐induced PNDs in adult mice after surgery/sevoflurane. Conclusion: Overall, our results have demonstrated a vital role for the LC‐dCA1 pathway in CSDS‐induced PNDs in adult mice undergoing surgery with sevoflurane anesthesia. [ABSTRACT FROM AUTHOR]

Dysfunctional fear responses in post-traumatic stress disorder (PTSD) may be partly explained by an inability to effectively extinguish fear responses elicited by trauma-related cues. However, only a subset of individuals exposed to traumatic stress develop PTSD. Therefore, studying fear extinction deficits in animal models of individual differences could help identify neural substrates underlying vulnerability or resilience to the effects of stress. We used a rat model of social defeat in which rats segregate into passively and actively coping rats. In previous work, we showed that passively coping rats exhibit disruptions in social interaction whereas actively coping rats do not display behaviors differently from controls, indicating their resilience. Here, adult male rats exposed to 7 days of social defeat were tested for fear extinction, retention of extinction, and persistence of retention using contextual fear and ethologically-relevant fear tests. Passively coping rats exhibited elevated freezing in response to the previously extinguished context. Analyses of cFos expressing cells across select brain regions showed high correlations within dorsal hippocampal subregions, while passively coping rats had high correlations between the dorsal hippocampus CA1 and the central and basolateral subregions of the amygdala. Importantly, although control and actively coping rats showed similar levels of behavioral extinction, there was little similarity between activated structures, suggesting stress resilience in response to chronic social defeat involves an adaptive differential recruitment of brain circuits to successfully extinguish fear memories. [ABSTRACT FROM AUTHOR]

The rapid relief of depressive symptoms is a major medical requirement for effective treatments for major depressive disorder (MDD). A decrease in neuroactive steroids contributes to the pathophysiological mechanisms associated with the neurological symptoms of MDD. Zuranolone (SAGE-217), a neuroactive steroid that acts as a positive allosteric modulator of synaptic and extrasynaptic d-subunit-containing GABAA receptors, has shown rapid-onset, clinically effective antidepressant action in patients with MDD or postpartum depression (PPD). Benzodiazepines, on the other hand, act as positive allosteric modulators of synaptic GABAA receptors but are not approved for the treatment of patients with MDD. It remains unclear how differences in molecular mechanisms contribute to the alleviation of depressive symptoms and the regulation of associated neuronal activity. Focusing on the antidepressant-like effects and neuronal activity of the basolateral amygdala (BLA) and medial prefrontal cortex (mPFC), we conducted a head-to-head comparison study of the neuroactive steroid allopregnanolone and the benzodiazepine diazepam using a mouse social defeat stress (SDS) model. Allopregnanolone but not diazepam exhibited antidepressant-like effects in a social interaction test in SDS mice. This antidepressant-like effect of allopregnanolone was abolished in extrasynaptic GABAA receptor d-subunit knockout mice (dKO mice) subjected to the same SDS protocol. Regarding the neurophysiological mechanism associated with these antidepressant-like effects, allopregnanolone but not diazepam increased theta oscillation in the BLA of SDS mice. This increase did not occur in dKO mice. Consistent with this, allopregnanolone potentiated tonic inhibition in BLA interneurons via d-subunit-containing extrasynaptic GABAA receptors. Theta oscillation in the mPFC of SDS mice was also increased by allopregnanolone but not by diazepam. Finally, allopregnanolone but not diazepam increased frontal theta activity in electroencephalography recordings in naïve and SDS mice. Neuronal network alterations associated with MDD showed decreased frontal theta and beta activity in depressed SDS mice. These results demonstrated that, unlike benzodiazepines, neuroactive steroids increased theta oscillation in the BLA and mPFC through the activation of d-subunit-containing GABAA receptors, and this change was associated with antidepressant-like effects in the SDS model. Our findings support the notion that the distinctive mechanism of neuroactive steroids may contribute to the rapid antidepressant effects in MDD. [ABSTRACT FROM AUTHOR]

Background: Chronic postsurgical pain (CPP) markedly impairs patients' quality of life. Research has shown that chronic stress may extend incisional nociception in male mice. Dopaminergic (DAergic) neurons in the ventral tegmental area (VTA) are integral to stress-related mental disorders (including major depressive disorder, anxiety disorders, and PTSD) and pain. However, the impact of chronic social defeat stress (CSDS) on mesolimbic dopamine (DA) transmission in the development of CPP is yet to be established. It remains uncertain whether the dopamine signals in the rostral anterior cingulate cortex (rACC), which regulate pain, derive from the VTA. This study aims to explore the role of VTA-rACC dopaminergic circuits in a mouse model of CPP induced by CSDS. Methods: We conducted CSDS on C57BL/6 J wild-type male mice (n = 12–16 mice/group) and DAT-cre male mice (n = 10–12 mice/group). After 10 days of CSDS, a left posterior plantar incision was made to establish a mouse model of CPP. Paw withdrawal thresholds (PWTs) were evaluated using Von-Frey fibre stimulation. The open field test (OFT) and elevated plus maze test (EPM) were used to assess pain-related negative emotions. We used immunofluorescence staining and Western Blot to analyse D1, D2, c-Fos, and TH expression. DAergic fibre projections in the VTA-rACC neural pathway were traced using retrograde tracing and immunofluorescence staining. Optogenetics and Chemogenetics were employed to manipulate DAergic neurons in the VTA and their axons in the rACC. Results: The ipsilateral PWTs in male C57BL/6 J mice significantly decreased after surgery, returning to baseline after seven days. Conversely, in CSDS mice, ipsilateral PWTs remained reduced for at least 30 days post-incision. A significant reduction in TH-positive neurons expressing c-Fos in the VTA of CPP mice was observed 15 days post-incision. Activating DAergic neurons significantly improved ipsilateral PWTs and locomotor performance in the OFT and EPM in CPP mice post-incision. Additionally, D1 expression in the rACC was found to decrease in CPP mice, and this reduction counteracted the increase in PWTs caused by activating DAergic neuron axon terminals in the rACC. Conclusion: CSDS results in chronicity of postsurgical nociception and anxiety-like negative emotions, with alterations in DA transmission playing a role in CPP. Specific activation of DAergic neurons mitigates nociceptive responses and anxiety-like bahaviors, possibly mediated by D1 receptors in the rACC. [ABSTRACT FROM AUTHOR]

Background: Major depressive disorder (MDD) is a common but severe psychiatric illness characterized by depressive mood and diminished interest. Both nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 1 (NLRP1) inflammasome and autophagy have been reported to implicate in the pathological processes of depression. However, the mechanistic interplay between NLRP1 inflammasome, autophagy, and depression is still poorly known. Methods: Animal model of depression was established by chronic social defeat stress (CSDS). Depressive-like behaviors were determined by social interaction test (SIT), sucrose preference test (SPT), open field test (OFT), forced swim test (FST), and tail-suspension test (TST). The protein expression levels of NLRP1 inflammasome complexes, pro-inflammatory cytokines, phosphorylated-phosphatidylinositol 3-kinase (p-PI3K)/PI3K, phosphorylated-AKT (p-AKT)/AKT, phosphorylated-mechanistic target of rapamycin (p-mTOR)/mTOR, brain-derived neurotrophic factor (BDNF), phosphorylated-tyrosine kinase receptor B (p-TrkB)/TrkB, Bcl-2-associated X protein (Bax)/B-cell lymphoma-2 (Bcl2) and cleaved cysteinyl aspartate-specific proteinase-3 (caspase-3) were examined by western blotting. The mRNA expression levels of pro-inflammatory cytokines were tested by quantitative real-time PCR. The interaction between proteins was detected by immunofluorescence and coimmunoprecipitation. Neuronal injury was assessed by Nissl staining. The autophagosomes were visualized by transmission electron microscopy. Nlrp1a knockdown was performed using an adeno-associated virus (AAV) vector containing Nlrp1a–shRNA–eGFP infusion. Results: CSDS exposure caused a bidirectional change in hippocampal autophagy function, which was activated in the initial period but impaired at the later stage. In addition, CSDS exposure increased the expression levels of hippocampal NLRP1 inflammasome complexes, pro-inflammatory cytokines, p-PI3K, p-AKT and p-mTOR in a time-dependent manner. Interestingly, NLRP1 is immunoprecipitated with mTOR but not PI3K/AKT and CSDS exposure facilitated the immunoprecipitation between them. Hippocampal Nlrp1a knockdown inhibited the activity of PI3K/AKT/mTOR signaling, rescued the impaired autophagy and ameliorated depressive-like behavior induced by CSDS. In addition, rapamycin, an autophagy inducer, abolished NLRP1 inflammasome-driven inflammatory reactions, alleviated depressive-like behavior and exerted a neuroprotective effect. Conclusions: Autophagy dysfunction contributes to NLRP1 inflammasome-linked depressive-like behavior in mice and the regulation of autophagy could be a valuable therapeutic strategy for the management of depression. [ABSTRACT FROM AUTHOR]

Objective: Microtubule (MT) stability in neurons is vital for brain development; instability is associated with neuropsychiatric disorders. The present study examined the effects of social defeat stress (SDS) on MT-regulating proteins and tubulin polymerization. Methods: After 10 days of SDS, defeated mice were separated into susceptible (Sus) and unsusceptible (Uns) groups based on their performance in a social avoidance test. Using extracted brain tissues, we measured the expression levels of α-tubulin, acetylated α-tubulin, tyrosinated α-tubulin, MT-associated protein-2 (MAP2), stathmin (STMN1), phospho stathmin serine 16 (p-STMN1 [Ser16]), phospho stathmin serine 25 (p-STMN1 [Ser25]), phospho stathmin serine 38 (p-STMN1 [Ser38]), stathmin2 (STMN2), phospho stathmin 2 serine 73 (p-STMN2 [Ser73]), 78-kDa glucose-regulated protein (GRP-78), and CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) using Western blot assay. The tubulin polymerization rate was also measured. Results: We observed increased and decreased expression of acetylated and tyrosinated α-tubulin, respectively, decreased expression of p-STMN1 (Ser16) and increased expression of p-STMN1 (Ser25), p-STMN2 (Ser73) and GRP-78 and CHOP in the prefrontal cortex and/or hippocampus of defeated mice. A reduced tubulin polymerization rate was observed in the Sus group compared to the Uns and Con groups. Conclusion: Our findings suggest that SDS has detrimental effects on MT stability, and a lower tubulin polymerization rate could be a molecular marker for susceptibility to SDS. [ABSTRACT FROM AUTHOR]

There is a high frequency of comorbidity of alcohol use disorder (AUD) and depression in human populations. We have studied this relationship in our lab using the social defeat stress (SDS) model, which results in both depression‐like behaviours and increased alcohol consumption in male mice. However, standard SDS procedures are difficult to use in female mice due to a lack of territorial aggression. In the experiments presented here, we used vicarious defeat stress (VDS) to assess social withdrawal and alcohol consumption in female C57BL6/J mice. We also assessed the expression of interleukin‐6 (IL6), which is a proinflammatory cytokine that is associated with depression in humans and sensitivity to SDS in mice. In these experiments, C57BL/6 female mice underwent 10 days of VDS where they witnessed the physical defeat of a male conspecific by an aggressive CD1 mouse. After the end of VDS, mice were either given access to alcohol or sacrificed for the measurement of IL6 expression. We found that VDS increased alcohol consumption and IL6 expression in the frontal cortex and hippocampus. Given that the neurokinin‐1 receptor (NK1R) can mediate both stress‐induced alcohol consumption and IL6 expression, we tested the ability of NK1R antagonism to reduce VDS‐induced alcohol consumption and found that this treatment reduced alcohol intake in both VDS‐exposed mice and in unstressed controls. The observed increase in alcohol consumption suggests that VDS is a model that can be utilized to study stress‐induced alcohol consumption in female mice, and that this is sensitive to NK1R antagonism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Neuronal activation and myelopoiesis after RSD were unaffected by P2X7 antagonism. • Increased Iba-1 proportional area after RSD was attenuated with P2X7 antagonism. • RSD increased monocytes (CD45+) in the brain and was prevented by P2X7 antagonism. • RSD increased immune signaling gene expression in the hippocampus and amygdala. • RSD-induced anxiety-like behavior was reversed by P2X7 antagonism. Chronic stress is linked to increased anxiety. Repeated social defeat (RSD) in mice causes anxiety that is dependent on activated neurons, reactive microglia, and accumulation of monocytes in the brain. This response requires interactions between the immune system and central nervous system (CNS). Neuronal activation within threat appraisal regions is a key response to RSD, however, it is unclear how microglia become activated. One potential explanation is that microglia express a purinergic non-selective ligand gated adenosine-triphosphate (ATP) receptor 7 (P2X7). Activation of P2X7 promotes the release of chemokines and cytokines, and recruitment of monocytes to the brain. Thus, the purpose of this study was to determine if a novel P2X7 antagonist blocked neuronal and microglia interactions and the corresponding anxiety following RSD. Male mice were administered (i.p.) a P2X7 antagonist, JNJ-54471300, prior to each cycle of RSD. Fourteen hours after RSD, behavioral deficits including social avoidance and anxiety-like were determined. Moreover, several immune parameters were assessed. RSD caused neuronal activation in stress-responsive regions, monocyte production and release, splenomegaly, and social avoidance. These parameters were unaffected by P2X7 antagonism. RSD-associated proportional area of Iba-1+ microglia, monocyte accumulation in the brain, IL-1β mRNA expression in enriched myeloid cells, plasma IL-6, and anxiety-like behavior were ameliorated by P2X7 antagonism. Gene expression analysis in the hippocampus and amygdala showed regional specific responses to RSD and some were reversed with P2X7 antagonism. Overall, blocking P2X7 activation attenuated RSD-induced microglia reactivity with corresponding reduction in neuroinflammation, monocyte accumulation, and anxiety-like behavior in male mice. [ABSTRACT FROM AUTHOR]

Adolescence is a unique period of psychosocial growth during which social adversity can negatively influence mental health trajectories. Understanding how adolescent social stress impacts males and females and why some individuals are particularly affected is becoming increasingly urgent. Social defeat stress models for adolescent male mice have been effective in reproducing some physical/psychological aspects of bullying. Designing a model suitable for females has proven challenging. We report a version of the adolescent male accelerated social defeat stress (AcSD) paradigm adapted for females. Early adolescent C57BL/6J female mice (N = 107) were exposed to our modified AcSD procedure twice a day for 4 days and categorized as resilient or susceptible based on a social interaction test 24 hours later. Mice were then assessed for changes in Netrin-1/DCC guidance cue expression in dopamine systems, for inhibitory control in adulthood using the Go/No-Go task, or for alterations in dopamine connectivity organization in the matured prefrontal cortex. Most adolescent females showed protection against stress-induced social avoidance, but in adulthood, these resilient females developed inhibitory control deficits and showed diminution of prefrontal cortex presynaptic dopamine sites. Female mice classified as susceptible were protected against cognitive and dopaminergic alterations. AcSD did not alter Netrin-1/DCC in early adolescent females, contrary to previous findings with males. Preserving prosocial behavior in adolescent females may be important for survival advantage but seems to come at the price of developing persistent cognitive and dopamine deficiencies. The female AcSD paradigm produced findings comparable to those found in males, allowing mechanistic investigation in both sexes. [ABSTRACT FROM AUTHOR]

Background Depression is a neuropsychiatric disease with a high disability rate and mainly caused by the chronic stress or genetic factors. There is increasing evidence that microRNAs (miRNAs) play a critical role in the pathogenesis of depression. However, the underlying molecular mechanism for the pathophysiology of depression of miRNA remains entirely unclear so far. Methods We first established a chronic social defeat stress (CSDS) mice model of depression, and depression-like behaviors of mice were evaluated by a series of behavioral tests. Next, we detected several abundantly expressive miRNAs suggested in previous reports to be involved in depression and found miR-182-5p was selected as a candidate for analysis in the hippocampus. Then western blotting and immunofluorescence were used together to examine whether adeno-associated virus (AAV)-siR-182-5p treatment alleviated chronic stress–induced decrease in hippocampal Akt/GSK3β/cAMP-response element binding protein (CREB) signaling pathway and increase in neurogenesis impairment and neuroinflammation. Furthermore, CREB inhibitor was adopted to examine if blockade of Akt/GSK3β/CREB signaling pathway abolished the antidepressant actions of AAV-siR-182-5p in mice. Results Knockdown of miR-182-5p alleviated depression-like behaviors and impaired neurogenesis of CSDS-induced mice. Intriguingly, the usage of agomiR-182-5p produced significant increases in immobility times and aggravated neuronal neurogenesis damage of mice. More importantly, it suggested that 666-15 blocked the reversal effects of AAV-siR-182-5p on the CSDS-induced depressive-like behaviors in behavioral testing and neuronal neurogenesis within hippocampus of mice. Conclusions These findings indicated that hippocampal miR-182-5p/Akt/GSK3β/CREB signaling pathway participated in the pathogenesis of depression, and it might give more opportunities for new drug developments based on the miRNA target in the clinic. [ABSTRACT FROM AUTHOR]

Extensive research reveals gender gaps in social media expression, particularly women's reduced propensity for sharing political information and opinions. We examine the impact of political defeat on the gender gap in political expression on social media by pairing Twitter data from candidate supporters with a voter file. Our results indicate that Trump's 2020 defeat reduced tweet volumes only among his female supporters, while his male supporters remained unaffected. This dampening effect was stronger for female Trump supporters who expressed their gender identity in their Twitter bios than those who did not. Tweet content remained largely unchanged for both genders. These findings enhance our understanding of how social media and political defeat together contribute to the gender expression gap and its relationship with offline political behaviors post-defeat. They also demonstrate the power of our methodological approach in revealing temporal and individual differences. [ABSTRACT FROM AUTHOR]

Despite the initial successes of the Bacillus Calmette-Guerin (BCG) vaccine in children, its efficacy against tuberculosis is highly variable. There is a lack of understanding about how mental conditions influence BCG vaccination. Here, we used the chronic social defeat stress (CSDS) model to explore the effects of depression on BCG vaccination efficacy. We observed higher lung and spleen bacterial loads and a lower organ index in depressed compared to BCG mice. Meanwhile, a relatively lower T cell protective efficacy was observed in both compared to control and BCG mice via a mycobacterium growth inhibition assay (MGIA). Cytokine expression of IL-12p40, IL-1β, IL-17, TNF-α and IFN-γ was reduced, whereas the expression of IL-10 and IL-5 was increased in the spleen of both compared to BCG mice. Moreover, the proportions of CD4+IFN-γ+, CD8+IFN-γ+ T lymphocytes and CD4+ effector/central memory T cells were reduced in the splenocytes of the depressed BCG mice. Depression promotes CD4+ regulatory T cells (Treg) and myeloid-derived suppressor cell (MDSC) generation in depressed mice, contributing to the reduced pro-inflammatory immune response upon BCG vaccination. This study provides insight into the decreased protective immunity by BCG vaccination attributable to depression in mice. [ABSTRACT FROM AUTHOR]

The role of altered brain mitochondrial regulation in psychiatric pathologies, including Major Depressive Disorder (MDD), has attracted increasing attention. Aberrant mitochondrial functions were suggested to underlie distinct inter-individual vulnerability to stress-related MDD syndrome. In this context, insulin receptor sensitizers (IRSs) that regulate brain metabolism have become a focus of recent research, as their use in pre-clinical studies can help to elucidate the role of mitochondrial dynamics in this disorder and contribute to the development of new antidepressant treatment. Here, following 2-week chronic mild stress (CMS) using predation, social defeat, and restraint, MDD-related behaviour and brain molecular markers have been investigated along with the hippocampus-dependent performance and emotionality in mice that received the IRS dicholine succinate (DS). In a sucrose test, mice were studied for the key feature of MDD, a decreased sensitivity to reward, called anhedonia. Based on this test, animals were assigned to anhedonic and resilient-to-stress-induced-anhedonia groups, using a previously established criterion of a decrease in sucrose preference below 65%. Such assignment was based on the fact that none of control, non-stressed animals displayed sucrose preference that would be smaller than this value. DS-treated stressed mice displayed ameliorated behaviours in a battery of assays: sucrose preference, coat state, the Y-maze, the marble test, tail suspension, and nest building. CMS-vulnerable mice exhibited overexpression of the inflammatory markers Il-1β, tnf, and Cox-1, as well as 5-htt and 5-ht2a-R, in various brain regions. The alterations in hippocampal gene expression were the closest to clinical findings and were studied further. DS-treated, stressed mice showed normalised hippocampal expression of the plasticity markers Camk4, Camk2, Pka, Adcy1, Creb-ar, Nmda-2r-ar, and Nmda-2r-s. DS-treated and non-treated stressed mice who were resilient or vulnerable to anhedonia were compared for hippocampal mitochondrial pathway regulation using Illumina profiling. Resilient mice revealed overexpression of the mitochondrial complexes NADH dehydrogenase, succinate dehydrogenase, cytochrome bc1, cytochrome c oxidase, F-type and V-type ATPases, and inorganic pyrophosphatase, which were decreased in anhedonic mice. DS partially normalised the expression of both ATPases. We conclude that hippocampal reduction in ATP synthesis is associated with anhedonia and pro-inflammatory brain changes that are ameliorated by DS. [ABSTRACT FROM AUTHOR]

Background: Bullying increases risk of social anxiety and can produce symptoms of posttraumatic stress disorder (PTSD). According to cognitive models, these are maintained by unhelpful beliefs, which are therefore assessed and targeted in cognitive therapy. This paper describes psychometric validation of a new measure of beliefs related to bullying experiences. Methods: In an online survey of 1879 young people before starting university or college in the UK, 1279 reported a history of bullying (N = 1279), and 854 rated their agreement with beliefs about self and others related to bullying experiences and completed symptom measures of social anxiety and PTSD related to bullying. An empirical structure for a Bullied Cognitions Inventory was established using exploratory and confirmatory factor analyses and assessed using model fit statistics and tests of reliability and validity. Results: Fifteen items clustered into four themes: "degraded in the eyes of others", "negative interpretations of reactions to bullying", "recognisable as a bullying victim" and "social defeat". The measure has acceptable reliability and validity and, accounting for existing cognitive measures, explained additional variance in symptoms of PTSD but not social anxiety. Conclusions: The Bullied Cognitions Inventory (BCI) is a valid and reliable tool for measuring cognitions related to bullying. It may be useful in therapy for identifying and monitoring unhelpful cognitions in those who were bullied. [ABSTRACT FROM AUTHOR]

Background: The stressful minority position of transgender persons may result in a high risk of psychosis. Conflicting data suggest that the observed risk depends on setting of recruitment. We assessed the relative risk of non-affective psychotic disorder (NAPD) in a large, representative cohort of transgender persons. Methods: This cohort was composed using: data on legal sex change from the Dutch population registry and data on dispensing of cross-sex hormones (route 1), and a registry of insurance claims from mental health care including persons with a diagnosis of gender identity disorder (DSM-IV) or gender dysphoria (DSM-5) (route 2). They were matched by sex at birth, calendar year and country of birth to controls from the general population. Transgender persons (N = 5564) and controls (N = 27 820), aged 16–60 years at 1 January 2011, were followed until the first insurance claim for NAPD in 2011–2019. Results: The incidence rate ratio (IRR) of NAPD for transgender persons selected exclusively through route 1 (N = 3859, IRR = 2.00, 95%-CI 1.52–2.63) was increased, but significantly lower than the IRRs for those selected exclusively through route 2 (N = 694, IRR = 22.15, 95%-CI 13.91–35.28) and for those found by both routes (N = 1011, IRR = 5.17, 95%-CI 3.57–7.49; p value for differences in IRR < 0.001). Conclusions: This study supports the social defeat-hypothesis of NAPD. The results also show the presence of a substantial number of transgender persons with severe psychiatric problems who have not (yet) taken steps to gender-affirmative care. [ABSTRACT FROM AUTHOR]

Previous studies showed that the dorsal premammillary nucleus of the hypothalamus (PMD) is involved in social passive defensive behaviors likely to be meditated by descending projections to the periaqueductal gray (PAG). We focused on the rostral dorsomedial PAG (rPAGdm) to reveal its putative neural mechanisms involved in mediating social defensive responses. By combining retrograde tracing and FOS expression analysis, we showed that in addition to the PMD, the rPAGdm is influenced by several brain sites active during social defeat. Next, we found that cytotoxic lesions of the rPAGdm drastically reduced passive defense and did not affect active defensive responses. We then examined the rPAGdm's projection pattern and found that the PAGdm projections are mostly restricted to midbrain sites, including the precommissural nucleus, different columns of the PAG, and the cuneiform nucleus (CUN). Also, we found decreased FOS expression in the caudal PAGdm, CUN, and PMD after the rPAGdm was lesioned. The results support that the rPAGdm mediates passive social defensive responses through ascending paths to prosencephalic circuits likely mediated by the CUN. This study provides further support for the role of the PAG in the modulation of behavioral responses by working as a unique hub for influencing prosencephalic sites during the mediation of aversive responses. [ABSTRACT FROM AUTHOR]

This Article brings new perspectives on the well-known Viking and Laval cases, decided by the Court of Justice of the European Union (CJEU) in December 2007, by studying the processes and modalities of the construction of this case law as a major defeat for social Europe. It demonstrates that the political and legal implications of these two rulings were socially constructed by a variety of European actors (especially trade unionists and academics specialising in labour law) rather than legally inscribed in the rulings. In doing so, the author defends a constructivist approach in the analysis of European case law, both contextual and processual. The Article is divided into two parts. The first retraces the pre-ruling construction of the Viking and Laval cases, and shows that trade union and academic actors as well as parliamentarians worked to construct the judgements on these cases as decisive landmarks for social Europe. The second part considers the process of interpretation of the rulings after they were delivered by the CJEU. It evidences the central role played by trade union and academic actors in promoting a critical reading of the rulings, arguing that the Court subordinated social rights to economic liberties. The Article concludes by showing that this interpretation has tended to become subject to consensus, to the extent that it is now European common sense. [ABSTRACT FROM AUTHOR]

Ample evidence has suggested the stress etiology of depression, but the underlying mechanism is not fully understood yet. Here, we report that chronic social defeat stress (CSDS) attenuates the excitatory output of the claustrum (CLA) to the prelimbic cortex (PL) through the dynorphin/κ-opioid receptor (KOR) signaling, being critical for depression-related behaviors in male mice. The CSDS preferentially impairs the excitatory output from the CLA onto the parvalbumin (PV) of the PL, leading to PL micronetwork dysfunction by disinhibiting pyramidal neurons (PNs). Optogenetic activation or inhibition of this circuit suppresses or promotes depressive-like behaviors, which is reversed by chemogenetic inhibition or activation of the PV neurons. Notably, manipulating the dynorphin/KOR signaling in the CLA-PL projecting terminals controls depressive-like behaviors that is suppressed or promoted by optogenetic activation or inhibition of CLA-PL circuit. Thus, this study reveals both mechanism of the stress etiology of depression and possibly therapeutic interventions by targeting CLA-PL circuit. The stress etiology of depression remains elusive. Here, authors show that dynorphin/KOR signaling-mediated impairment of excitatory synaptic transmission from claustrum to prelimbic cortex PV interneurons contributes to stress-induced depression. [ABSTRACT FROM AUTHOR]

Depression is a highly prevalent and disabling mental disorder, involving numerous genetic changes that are associated with abnormal functions in multiple regions of the brain. However, there is little transcriptomic‐wide characterization of chronic social defeat stress (CSDS) to comprehensively compare the transcriptional changes in multiple brain regions. Spatial transcriptomics (ST) was used to reveal the spatial difference of gene expression in the control, resilient (RES) and susceptible (SUS) mouse brains, and annotated eight anatomical brain regions and six cell types. The gene expression profiles uncovered that CSDS leads to gene synchrony changes in different brain regions. Then it was identified that inhibitory neurons and synaptic functions in multiple regions were primarily affected by CSDS. The brain regions Hippocampus (HIP), Isocortex, and Amygdala (AMY) present more pronounced transcriptional changes in genes associated with depressive psychiatric disorders than other regions. Signalling communication between these three brain regions may play a critical role in susceptibility to CSDS. Taken together, this study provides important new insights into CSDS susceptibility at the ST level, which offers a new approach for understanding and treating depression. [ABSTRACT FROM AUTHOR]

Several forms of social defeat, including ostracism, discrimination, bullying, and related experiences, have been associated with psychotic disorders and experiences. The social defeat hypothesis of schizophrenia attempts to explain these associations by positing that chronic exclusion due to having outsider status leads to deleterious neurobiological changes that produce psychosis. Here, we test non-neurobiological tenets of this theory, including the relative impact of daily, real-world, chronic social defeat versus an acute, time-limited, experimentally-induced socially defeating experience (social exclusion), the moderating role of psychosis-proneness, and the specificity of social defeat on psychosis-related outcomes. We find that real-world, chronic, but not acute, time-limited, laboratory-based social defeat is associated with decreased trust, but not false-alarms on an auditory signal detection task. These associations were qualified by interactions that are in line with social reconnection (i.e., positive appraisals of social stimuli following exclusion). Real-world, chronic social defeat was also associated with delusion- and hallucination-proneness. Together, these data highlight the importance of daily, real-world forms of social defeat versus laboratory manipulations on specific psychosis-related outcomes.

The article offers information on the collaboration between the Society for Neuroscience (SfN), ARTECHOUSE, and neurobiologists, resulting in the creation of Life of a Neuron, a digital art installation providing an immersive experience of a human neuron. Topics include the mentor–mentee relationship between D.D. and J.H.M., spanning a decade and a half of co-creative growth that contributed to the science behind Life of a Neuron.

Although regular exercise has been reported to prevent depression, it has not been clarified whether the gut microbiota is involved in the factors that prevent depression through exercise. We investigated the effects of voluntary exercise on the gut microbiota and the prevention of depression-like behaviors using mice. C57BL/6 J male mice were subjected to 10 weeks of sedentary control or wheel running, then they were subjected to social defeat stress (SDS). Exercise attenuated that sucrose drinking was decreased by SDS treatment. Exercise increased the expression of Bdnf and decreased expression of Zo-1 and Claudin5 in the brain. Fecal Turicibacter, Allobaculum, and Clostridium sensu stricto, and propionate in the cecum were decreased by the exercise. Voluntary exercise-induced antidepressant properties might be partially caused by suppression of serotonin uptake into gut microbiota and increase the permeability of the blood-brain barrier via reduced propionate production. [ABSTRACT FROM AUTHOR]

• Ketogenic diet tends to promote resistance to psychological stress. • Hippocampal microglia show morphological adaptations to stress and diet. • Microglia of stress-susceptible mice make less synaptic contacts. • Microglia of ketogenic diet-fed mice show less signs of cellular stress. • Lipids are differentially regulated in the hippocampi of susceptible mice. Psychological stress confers an increased risk for several diseases including psychiatric conditions. The susceptibility to psychological stress is modulated by various factors, many of them being modifiable lifestyle choices. The ketogenic diet (KD) has emerged as a dietary regime that offers positive outcomes on mood and health status. Psychological stress and elevated inflammation are common features of neuropsychiatric disorders such as certain types of major depressive disorder. KD has been attributed anti-inflammatory properties that could underlie its beneficial consequences on the brain and behavior. Microglia are the main drivers of inflammation in the central nervous system. They are known to respond to both dietary changes and psychological stress, notably by modifying their production of cytokines and relationships among the brain parenchyma. To assess the interactions between KD and the stress response, including effects on microglia, we examined adult male mice on control diet (CD) versus KD that underwent 10 days of repeated social defeat (RSD) or remained non-stressed (controls; CTRLs). Through a social interaction test, stressed mice were classified as susceptible (SUS) or resistant (RES) to RSD. The mouse population fed a KD tended to have a higher proportion of individuals classified as RES following RSD. Microglial morphology and ultrastructure were then analyzed in the ventral hippocampus CA1, a brain region known to present structural alterations as a response to psychological stress. Distinct changes in microglial soma and arborization linked to the KD, SUS and RES phenotypes were revealed. Ultrastructural analysis by electron microscopy showed a clear reduction of cellular stress markers in microglia from KD fed animals. Furthermore, ultrastructural analysis showed that microglial contacts with synaptic elements were reduced in the SUS compared to the RES and CTRL groups. Hippocampal lipidomic analyses lastly identified a distinct lipid profile in SUS animals compared to CTRLs. These key differences, combined with the distinct microglial responses to diet and stress, indicate that unique metabolic changes may underlie the stress susceptibility phenotypes. Altogether, our results reveal novel mechanisms by which a KD might improve the resistance to psychological stress. [ABSTRACT FROM AUTHOR]

Anxiety disorders are a major public health concern and current treatments are inadequate for many individuals. Anxiety is more common in women than men and this difference arises during puberty. Sex differences in physiological stress responses may contribute to this variability. During puberty, gonadal hormones shape brain structure and function, but the extent to which these changes affect stress sensitivity is unknown. We examined how pubertal androgens shape behavioral and neural responses to social stress in California mice (Peromyscus californicus), a model species for studying sex differences in stress responses. In adults, social defeat reduces social approach and increases social vigilance in females but not males. We show this sex difference is absent in juveniles, and that prepubertal castration sensitizes adult males to social defeat. Adult gonadectomy does not alter behavioral responses to defeat, indicating that gonadal hormones act during puberty to program behavioral responses to stress in adulthood. Calcium imaging in the medioventral bed nucleus of the stria terminalis (BNST) showed that social threats increased neural activity and that prepubertal castration generalized these responses to less threatening social contexts. These results support recent hypotheses that the BNST responds to immediate threats. Prepubertal treatment with the nonaromatizable androgen dihydrotestosterone acts in males and females to reduce the effects of defeat on social approach and vigilance in adults. These data indicate that activation of androgen receptors during puberty is critical for programming behavioral responses to stress in adulthood. [ABSTRACT FROM AUTHOR]

The salt-inducible kinase 1 (SIK1)-CREB-regulated transcription co-activator 1 (CRTC1) system in the paraventricular nucleus (PVN) of the hypothalamus has been demonstrated to participate in not only depression neurobiology but also the antidepressant mechanisms of fluoxetine, paroxetine, venlafaxine, and duloxetine. Like fluoxetine and paroxetine, escitalopram is also a well-known selective serotonin (5-HT) reuptake inhibitor (SSRI). However, recently it has been found that escitalopram can modulate a lot of targets other than the 5-HT system. Here, we speculate that escitalopram produces effects on the SIK1-CRTC1 system in the PVN. Two mice models of depression (chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS)), various behavioral tests, enzyme linked immunosorbent assay (ELISA), western blotting, co-immunoprecipitation (Co-IP), quantitative real-time reverse transcription PCR (qRT-PCR), immunofluorescence, and adeno-associated virus (AAV)-mediated gene transfer were used together in the present study. It was found that escitalopram administration not only significantly prevented the hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis induced by CSDS and CUMS, but also notably reversed the effects of CSDS and CUMS on SIK1, CRTC1, and CRTC1-CREB binding in the PVN of mice. AAV-based genetic knock-down of SIK1 in PVN neurons evidently abolished the antidepressant-like effects of escitalopram in mice. A shortage of this study is that only rodent models of depression were used, while human samples were not included. In summary, regulating the SIK1-CRTC1 system in the PVN participates in the antidepressant mechanism of escitalopram, which extends the knowledge of the pharmacological actions of escitalopram. • Escitalopram treatment antagonized the effects of CSDS on SIK1 and CRTC1 in the PVN. • Escitalopram treatment antagonized the effects of CUMS on SIK1 and CRTC1 in the PVN. • Knock-down of SIK1 in the PVN abolished the antidepressant-like effects of escitalopram. [ABSTRACT FROM AUTHOR]

Background Although thought of as a multimodal-acting antidepressant targeting the serotonin system, more molecules are being shown to participate in the antidepressant mechanism of vortioxetine. A previous report has shown that vortioxetine administration enhanced the expression of rapamycin complex 1 (mTORC1) in neurons. It has been well demonstrated that mTORC1 participates in not only the pathogenesis of depression but also the pharmacological mechanisms of many antidepressants. Therefore, we speculate that the antidepressant mechanism of vortioxetine may require mTORC1. Methods Two mouse models of depression (chronic social defeat stress and chronic unpredictable mild stress) and western blotting were first used together to examine whether vortioxetine administration produced reversal effects against the chronic stress–induced downregulation in the whole mTORC1 signaling cascade in both the hippocampus and medial prefrontal cortex (mPFC). Then, LY294002, U0126, and rapamycin were used together to explore whether the antidepressant effects of vortioxetine in mouse models of depression were attenuated by pharmacological blockade of the mTORC1 system. Furthermore, lentiviral-mTORC1-short hairpin RNA-enhanced green fluorescence protein (LV-mTORC1-shRNA-EGFP) was adopted to examine if genetic blockade of mTORC1 also abolished the antidepressant actions of vortioxetine in mice. Results Vortioxetine administration produced significant reversal effects against the chronic stress–induced downregulation in the whole mTORC1 signaling cascade in both the hippocampus and mPFC. Both pharmacological and genetic blockade of the mTORC1 system notably attenuated the antidepressant effects of vortioxetine in mice. Conclusions Activation of the mTORC1 system in the hippocampus and mPFC is required for the antidepressant actions of vortioxetine in mice. [ABSTRACT FROM AUTHOR]

Stress is an important aspect of our everyday life and exposure to it is an unavoidable occurrence. In humans, this can come in the form of social stress or physical stress from an injury. Studies in animal models have helped researchers to understand the body's adaptive response to stress in human. Notably, the use of behavioural tests in animal models plays a pivotal role in understanding the neural, endocrine and behavioural changes induced by social stress. Under socially stressed conditions, behavioural parameters are often measured physiological and molecular parameters as changes in behaviour are direct responses to stress and are easily assessed by behavioural tests. Throughout the past few decades, the rodent model has been used as a well-established animal model for stress and behavioural changes. Recently, more attention has been drawn towards using fish as an animal model. Common fish models such as zebrafish, medaka, and African cichlids have the advantage of a higher rate of reproduction, easier handling techniques, sociability and most importantly, share evolutionary conserved genetic make-up, neural circuitry, neuropeptide molecular structure and function with mammalian species. In fact, some fish species exhibit a clear diurnal or seasonal rhythmicity in their stress response, similar to humans, as opposed to rodents. Various social stress models have been established in fish including but not limited to chronic social defeat stress, social stress avoidance, and social stressrelated decision-making. The huge variety of behavioural patterns in teleost also aids in the study of more behavioural phenotypes than the mammalian species. In this review, we focus on the use of fish models as alternative models to study the effects of stress on different types of behaviours. Finally, fish behavioural tests against the typical mammalian model-based behavioural test are compared and discussed for their viability. [ABSTRACT FROM AUTHOR]