Overlapping neurobiology of learned helplessness and conditioned defeat: implications for PTSD and mood disorders

Multiple Sex- and Circuit-Specific Mechanisms Underlie Exercise-Induced Stress Resistance

Prior physical activity reduces the risk of future stress-related mental health disorders including depression, anxiety, and post-traumatic stress disorder. Rodents allowed to engage in voluntary wheel running are similarly protected from behavioral consequences of stress. The present review summarizes current knowledge on mechanisms underlying exercise-induced stress resistance. A conceptual framework involving the development (during exercise) and expression (during stress) of stress resistance from exercise is proposed. During the development of stress resistance, adaptations involving multiple exercise signals and molecular mediators occur within neural circuits orchestrating various components of the stress response, which then respond differently to stress during the expression of stress resistance. Recent data indicate that the development and expression of stress resistance from exercise involve multiple independent mechanisms that depend on sex, stressor severity, and behavioral outcome. Recent insight into the role of the prefrontal cortex in exercise-induced stress resistance illustrates these multiple mechanisms. This knowledge has important implications for the design of future experiments aimed at identifying the mechanisms underlying exercise-induced stress resistance.

Antidepressant effect and mechanism of TMP269 on stress-induced depressive-like behavior in mice

TMP269, a class IIA histone deacetylase inhibitor with selectivity, that has a protective effect on the central nervous system, yet its specific mechanism of action remains ambiguous. Although major depressive disorder (MDD) is highly prevalent, its pathophysiology is poorly understood. Recent evidence suggests that histone deacetylase 5 plays a key role in the pathological process of depression and the fact that preclinical studies have shown HDAC5 to be a potential antidepressant target, the search for natural drugs or small molecule compounds that can target HDAC5 may be a potential therapeutic strategy for the treatment of depression. In addition, we examined the role of the Brain-derived neurotrophic factor (BDNF), an important neurotrophic factor for neuronal survival and growth, as a potential downstream target of HDAC5. We found downward revision of HDAC5 levels in the hippocampus ameliorated depressive-like behavior in LH (Learned helplessness) mice. Furthermore, injection of HDAC5 overexpressing adenoviral vectors in the hippocampal dentate gyrus of wild-type mice produced a somewhat depressive-like phenotype. Pharmacological, immunofluorescence and biochemical experiments showed that TMP269 could produce antidepressant effects by inhibiting mouse hippocampal HDAC5 and thus modulating its downstream BDNF. Over all, TMP269 mitigated LH-induced depressive-like behaviors and abnormalities in synapse formation and neurogenesis within the hippocampus. These findings suggest potential beneficial effects of TMP269 on depression.

The role and mechanism of 5-HTDRN-BNST neural circuit in anxiety and fear lesions

Central 5-hydroxytryptaminergic dorsal raphe nucleus (5-HTDRN)-bed nucleus of stria terminalis (BNST) neural circuit dysfunction is one of the important neurobiological basis of anxiety and fear disorders. Under stress, 5-hydroxytryptamine (5-HT) neurons act on BNST receptors to attenuate anxiety and fear responses or enhance anxiety and fear. In BNST, corticotropin releasing factor neurons play a role in regulating emotions by reversely regulating excitatory or inhibitory 5-HT neurons. The composition of 5-HTDRN-BNST neural circuit, the pathological changes of 5-HTDRN-BNST neural circuit function damage under stress, and the effects of 5-HTDRN-BNST neural circuit on anxiety disorder, panic disorder and post-traumatic stress disorder were analyzed and are summarized in this paper. The characteristics of functional changes of the neural circuit and its effects on brain functional activities provide a basis and ideas for the treatment of anxiety and fear disorders through the regulation of 5-HTDRN-BNST neural circuit, and they also provide a new perspective for understanding the pathological mechanism of such diseases.

Maladaptation of dentate gyrus mossy cells mediates contextual discrimination deficit after traumatic stress

Fear overgeneralization is a maladaptive response to traumatic stress that is associated with the inability to discriminate between threat and safety contexts, a hallmark feature of post-traumatic stress disorder (PTSD). However, the neural mechanisms underlying this deficit remain unclear. Here, we show that traumatic stress exposure impairs contextual discrimination between threat and safety contexts in the learned helplessness (LH) model. Mossy cells (MCs) in the dorsal hippocampus are suppressed in response to traumatic stress. Bidirectional manipulation of MC activity in the LH model reveals that MC inhibition is causally linked to impaired contextual discrimination. Mechanistically, MC inhibition increases the number of active granule cells in a given context, significantly overlapping context-specific ensembles. Our study demonstrates that maladaptive inhibition of MCs after traumatic stress is a substantial mechanism underlying fear overgeneralization with contextual discrimination deficit, suggesting a potential therapeutic target for cognitive symptoms of PTSD.

Association between traumatic events with suicidality among adolescents: A large-scale cross-sectional study of 260,423 participants

Traumatic events have significant negative impacts throughout one's life. We aimed to comprehensively examine the early associations between traumatic events and suicidality among adolescents. In a cross-sectional sample of 260,423 adolescents in Deyang, China in September 2021, we assessed individual traumatic events, cumulative types, and patterns, alongside suicide risk scores and ideation, attempts, or plans. Linear and Poisson regression models adjusted for demographic confounders evaluated the association. Robust associations existed between interpersonal violence-related traumatic events and higher suicidality, with physical abuse demonstrating the strongest correlation. Moreover, suicide risk scores displayed a clear trend, indicating a progressively stronger association with suicidality as cumulative traumatic event types increased. Four distinct traumatic patterns emerged, including low traumas, high physical abuse, high death/serious injuries of a loved one, and multiple traumas, with the latter showing the strongest association with suicidality. Notably, the stratified analysis showed these associations were more pronounced in females, urban residents, only children, left-behind children, and those aged 13-15, while weaker in participants from families with intact parental relationships and middle socioeconomic status. Understanding the role of demographic factors and traumatic patterns in identifying at-risk youth can enable early detection and targeted interventions for suicide-related concerns.

Adolescents flexibly adapt action selection based on controllability inferences

From early in life, we encounter both controllable environments, in which our actions can causally influence the reward outcomes we experience, and uncontrollable environments, in which they cannot. Environmental controllability is theoretically proposed to organize our behavior. In controllable contexts, we can learn to proactively select instrumental actions that bring about desired outcomes. In uncontrollable environments, Pavlovian learning enables hard-wired, reflexive reactions to anticipated, motivationally salient events, providing "default" behavioral responses. Previous studies characterizing the balance between Pavlovian and instrumental learning systems across development have yielded divergent findings, with some studies observing heightened expression of Pavlovian learning during adolescence and others observing a reduced influence of Pavlovian learning during this developmental stage. In this study, we aimed to investigate whether a theoretical model of controllability-dependent arbitration between learning systems might explain these seemingly divergent findings in the developmental literature, with the specific hypothesis that adolescents' action selection might be particularly sensitive to environmental controllability. To test this hypothesis, 90 participants, aged 8-27, performed a probabilistic-learning task that enables estimation of Pavlovian influence on instrumental learning, across both controllable and uncontrollable conditions. We fit participants' data with a reinforcement-learning model in which controllability inferences adaptively modulate the dominance of Pavlovian versus instrumental control. Relative to children and adults, adolescents exhibited greater flexibility in calibrating the expression of Pavlovian bias to the degree of environmental controllability. These findings suggest that sensitivity to environmental reward statistics that organize motivated behavior may be heightened during adolescence.

Dimensional Reduction in Barriers and Facilitators to Pre-exposure Prophylaxis (PrEP) Uptake Willingness for Full-Service Sex Workers

Full-Service Sex Workers (FSSWs) face heightened risk of acquiring HIV, yet exhibit relatively low adoption of pre-exposure prophylaxis (PrEP)-an antiviral that substantially reduces HIV acquisition risk. Little work examines barriers and facilitators to PrEP uptake willingness among FSSWs. This study aimed to identify the distinct components of barriers and facilitators to PrEP uptake willingness for FSSWs. Here, we subjected 19 PrEP barriers and facilitators identified in the literature to a principal component analysis (PCA) among a sample of 83 FSSWs. Preliminary statistics supported factorability of data. PCA revealed three distinct components of barriers and facilitators that explained 62.80% of the total variance in survey responses. We labeled these components Behavioral and Social Concerns (α = 0.93), Access and Affordability (α = 0.67), and Biologically Based Health Concerns (α = 0.79). This study shows promise for future clinical and research utility of these factors and provides a basis for future psychometric studies of barriers and facilitators to PrEP uptake willingness among FSSWs.

Sex Differences in Complex Posttraumatic Stress Disorder Network among Chinese Young Adults

Evidence suggests that sex differences commonly occur in trauma-related disorders. The current study aims to explore sex differences in complex posttraumatic stress disorder (CPTSD) symptom networks among Chinese young adults with childhood trauma. The current study utilized a representative sample of college students in Beijing and included 1416 participants (409 men and 907 women) who had childhood trauma experience. CPTSD symptoms were evaluated using the International Trauma Questionnaire. Regularized partial correlation network analysis and Bayesian network analysis were used to estimate the network structure and possible causality of CPTSD symptoms for both sexes. Male and female CPTSD symptom networks had differences in strength centrality and bridge centrality. Nightmares and feelings of failure had the highest strength centrality, and long-term upset and nightmares had the highest bridge centrality for men. Hypervigilance and feelings of failure had the highest strength centrality, and long-term upset and exaggerated startle response had the highest bridge centrality for women. The current study provides the first evidence of sex differences in the CPTSD symptom network among Chinese young adults with childhood trauma. Young men and women differed in highly central symptoms, which may speak to sex specificity in the main manifestations of CPTSD symptoms.

Associations of crying, sleeping, and feeding problems in early childhood and perceived social support with emotional disorders in adulthood

BACKGROUND

Multiple or persistent crying, sleeping, or feeding problems in early childhood (regulatory problems) are associated with increased internalizing symptoms in adulthood. Unknown is whether early regulatory problems are associated with emotional disorders in adulthood, and what psychosocial factors may provide protection. We tested whether early childhood multiple or persistent regulatory problems are associated with a higher risk of (a) any mood and anxiety disorder in adulthood; (b) perceiving no social support in adulthood; and (c) whether social support provides protection from mood and anxiety disorders among participants who had multiple/persistent regulatory problems and those who never had regulatory problems.

METHODS

Data from two prospective longitudinal studies in Germany (n = 297) and Finland (n = 342) was included (N = 639). Regulatory problems were assessed at 5, 20, and 56 months with the same standardized parental interviews and neurological examinations. In adulthood (24-30 years), emotional disorders were assessed with diagnostic interviews and social support with questionnaires.

RESULTS

Children with multiple/persistent regulatory problems (n = 132) had a higher risk of any mood disorder (odds ratio (OR) = 1.81 [95% confidence interval = 1.01-3.23]) and of not having any social support from peers and friends (OR = 1.67 [1.07-2.58]) in adulthood than children who never had regulatory problems. Social support from peers and friends provided protection from mood disorders, but only among adults who never had regulatory problems (OR = 4.03 [2.16-7.94]; p = .039 for regulatory problems x social support interaction).

CONCLUSIONS

Children with multiple/persistent regulatory problems are at increased risk of mood disorders in young adulthood. Social support from peers and friends may, however, only provide protection from mood disorders in individuals who never had regulatory problems.

Comparing the ontogeny, neurobiology, and function of social play in hamsters and rats

Syrian hamsters show complex social play behavior and provide a valuable animal model for delineating the neurobiological mechanisms and functions of social play. In this review, we compare social play behavior of hamsters and rats and underlying neurobiological mechanisms. Juvenile rats play by competing for opportunities to pin one another and attack their partner's neck. A broad set of cortical, limbic, and striatal regions regulate the display of social play in rats. In hamsters, social play is characterized by attacks to the head in early puberty, which gradually transitions to the flanks in late puberty. The transition from juvenile social play to adult hamster aggression corresponds with engagement of neural ensembles controlling aggression. Play deprivation in rats and hamsters alters dendritic morphology in mPFC neurons and impairs flexible, context-dependent behavior in adulthood, which suggests these animals may have converged on a similar function for social play. Overall, dissecting the neurobiology of social play in hamsters and rats can provide a valuable comparative approach for evaluating the function of social play.

Trauma-Informed Care for Individuals with Intellectual and Developmental Disabilities: From Disparity to Policies for Effective Action

People with intellectual disabilities (ID) are an often overlooked minority population. They experience significant health disparities and a high risk of exposure to traumatic events that can lead to stress-related disorders. Access to effective treatments for stress-related disorders is limited for people with ID due to a lack of appropriate assessments and common communication deficits. We discuss and analyze four factors that have led to these disparities: (1) historical segregation; (2) society's response to identification of trauma in vulnerable populations; (3) lack of accessible assessments and treatments for stress disorders in people with ID; and (4) communication deficits common in people with ID. Based on this analysis, we suggest behavior analysts advocate for policy development that would (1) increase acknowledgement of trauma in people with ID and mandate sharing of information about trauma across providers; (2) require observable and measurable goals be included in the assessment and treatment of trauma-related behavior change; and (3) increase funding for services and research in this area.

Physical and social trauma: Towards an integrative transdiagnostic perspective on psychological trauma that involves threats to status and belonging

Current theories of psychological trauma assume that posttraumatic symptoms originate from stress reactions caused by extremely adverse life experiences. Since the diagnosis of PTSD is restricted to events that involve threats to the physical or sexual integrity of a person, such as accidents and physical and sexual violence, these theories are not well suited to explain the psychopathological consequences of severe violations of one's social integrity, such as emotional abuse and bullying. However, it is evident that social threats contribute to a broad range of mental disorders and increase symptom severity in patients with posttraumatic stress disorder. The aim of the Physical and Social Trauma (PAST) framework is to extend current memory theories of psychological trauma to incorporate threats to a person's social integrity. Within this perspective, the harmful effects of events that involve social threats result from violations of core social motives such as the need for status and belonging that bring about intense affective reactions, including despair and defeat. Within associative threat structures, these emotions are tied to the stimulus characteristics of the experiences and can be re-activated in social situations. The resulting psychopathology transcends PTSD criteria and other current classifications and suggests a transdiagnostic perspective of psychological trauma. Implications for treatment and further directions for research are discussed.

Ginsenoside Rg3 modulates spatial memory and fear memory extinction by the HPA axis and BDNF-TrkB pathway in a rat post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a serious mental disorder that can develop after exposure to extreme stress. Korean red ginseng, whose major active component is ginsenoside Rg3 (Rg3), is a widely used traditional antioxidant that has anti-inflammatory, anti-apoptotic and anxiolytics effects. This study investigated whether the administration of Rg3 ameliorated the memory deficit induced by a single prolonged stress (SPS) in rats. Male rats were dosed with Rg3 (25 or 50 mg/kg) once daily for 14 days after exposure to SPS. Rg3 administration improved fear memory and spatial memory might be involved in modulating the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and monoamine imbalance in the medial prefrontal cortex and hippocampus. It also increased the reduction in the brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) mRNAs expression, and the ratio of p-Akt/Akt in the hippocampus. Thus, Rg3 exerted memory-improving actions might be involved in regulating HPA axis and activating BDNF-TrkB pathway. Our findings suggest that Rg3 could be useful for preventing traumatic stress, such as PTSD.

Traumatic brain injury-induced submissive behavior in rats: link to depression and anxiety

Traumatic brain injury (TBI) affects millions of people worldwide, many of whom are affected with post-TBI mood disorders or behavioral changes, including aggression or social withdrawal. Diminished functionality can persist for decades after TBI and delay rehabilitation and resumption of employment. It has been established that there is a relationship between these mental disorders and brain injury. However, the etiology and causal relationships behind these conditions are poorly understood. Rodent models provide a helpful tool for researching mood disorders and social impairment due to their natural tendencies to form social hierarchies. Here, we present a rat model of mental complications after TBI using a suite of behavioral tests to examine the causal relationships between changes in social behavior, including aggressive, hierarchical, depressive, and anxious behavior. For this purpose, we used multivariate analysis to identify causal relationships between the above post-TBI psychiatric sequelae. We performed statistical analysis using principal component analysis, discriminant analysis, and correlation analysis, and built a model to predict dominant-submissive behavior based on the behavioral tests. This model displayed a predictive accuracy of 93.3% for determining dominant-submissive behavior in experimental groups. Machine learning algorithms determined that in rats, aggression is not a principal prognostic factor for dominant-submissive behavior. Alternatively, dominant-submissive behavior is determined solely by the rats' depressive-anxious state and exploratory activity. We expect the causal approach used in this study will guide future studies into mood conditions and behavioral changes following TBI.

The Anxiolytic-Like Effects of Protocatechuic Acid in an Animal Model of Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a serious psychiatric disorder characterized by impaired fear extinction, depression, and anxiety caused by dysregulation of the hypothalamic-pituitary-adrenal axis and an imbalance of monoamines. Protocatechuic acid (PCA; 3,4-dihydroxybenzoic acid), a major polyphenol metabolite, has various pharmacological effects, such as anti-inflammatory, antioxidant, anti-apoptotic, and neuroprotective activities. In this study, the efficacy of PCA for fear extinction, antidepressant, and anxiolytic effects in PTSD-mediated psychiatric disorders, were evaluated by exposing rats to single prolonged stress (SPS). Male rats were administered PCA (100 or 200 mg/kg) once daily for 14 days after exposure to SPS. PCA significantly decreased situational fear, depressive and anxiety-like behaviors, and corticosterone levels. In addition, PCA regulated the imbalance of serotonin and norepinephrine in the fear circuit region (i.e., the medial prefrontal cortex and hippocampus [Hipp]), and suppressed the decrease in brain-derived neurotrophic factor mRNA expression in the Hipp. The results showed that PCA administration improves freezing behavior and has antidepressant and anti-anxiety effects through modulation of the serotonergic nervous system and monoamines in rats. These results indicated that PCA may be useful as a food ingredient to prevent PTSD.

Stress-sensitive inference of task controllability

Estimating the controllability of the environment enables agents to better predict upcoming events and decide when to engage controlled action selection. How does the human brain estimate controllability? Trial-by-trial analysis of choices, decision times and neural activity in an explore-and-predict task demonstrate that humans solve this problem by comparing the predictions of an 'actor' model with those of a reduced 'spectator' model of their environment. Neural blood oxygen level-dependent responses within striatal and medial prefrontal areas tracked the instantaneous difference in the prediction errors generated by these two statistical learning models. Blood oxygen level-dependent activity in the posterior cingulate, temporoparietal and prefrontal cortices covaried with changes in estimated controllability. Exposure to inescapable stressors biased controllability estimates downward and increased reliance on the spectator model in an anxiety-dependent fashion. Taken together, these findings provide a mechanistic account of controllability inference and its distortion by stress exposure.

Spike firing attenuation of serotonin neurons in learned helplessness rats is reversed by ketamine

Animals suffering from uncontrollable stress sometimes show low effort to escape stress (learned helplessness). Changes in serotonin (5-hydroxytryptamine) signalling are thought to underlie this behaviour. Although the release of 5-hydroxytryptamine is triggered by the action potential firing of dorsal raphe nuclei 5-hydroxytryptamine neurons, the electrophysiological changes induced by uncontrollable stress are largely unclear. Herein, we examined electrophysiological differences among 5-hydroxytryptamine neurons in naïve rats, learned helplessness rats and rats resistant to inescapable stress (non-learned helplessness). Five-week-old male Sprague Dawley rats were exposed to inescapable foot shocks. After an avoidance test session, rats were classified as learned helplessness or non-learned helplessness. Activity-dependent 5-hydroxytryptamine release induced by the administration of high-potassium solution was slower in free-moving learned helplessness rats. Subthreshold electrophysiological properties of 5-hydroxytryptamine neurons were identical among the three rat groups, but the depolarization-induced spike firing was significantly attenuated in learned helplessness rats. To clarify the underlying mechanisms, potassium (K+) channels regulating the spike firing were initially examined using naïve rats. K+ channels sensitive to 500 μM tetraethylammonium caused rapid repolarization of the action potential and the small conductance calcium-activated K+ channels produced afterhyperpolarization. Additionally, dendrotoxin-I, a blocker of Kv1.1 (encoded by Kcna1), Kv1.2 (encoded by Kcna2) and Kv1.6 (encoded by Kcna6) voltage-dependent K+ channels, weakly enhanced the spike firing frequency during depolarizing current injections without changes in individual spike waveforms in naïve rats. We found that dendrotoxin-I significantly enhanced the spike firing of 5-hydroxytryptamine neurons in learned helplessness rats. Consequently, the difference in spike firing among the three rat groups was abolished in the presence of dendrotoxin-I. These results suggest that the upregulation of dendrotoxin-I-sensitive Kv1 channels underlies the firing attenuation of 5-hydroxytryptamine neurons in learned helplessness rats. We also found that the antidepressant ketamine facilitated the spike firing of 5-hydroxytryptamine neurons and abolished the firing difference between learned helplessness and non-learned helplessness by suppressing dendrotoxin-I-sensitive Kv1 channels. The dendrotoxin-I-sensitive Kv1 channel may be a potential target for developing drugs to control activity of 5-hydroxytryptamine neurons.

Environmental certainty influences the neural systems regulating responses to threat and stress

Flexible calibration of threat responding in accordance with the environment is an adaptive process that allows an animal to avoid harm while also maintaining engagement of other goal-directed actions. This calibration process, referred to as threat response regulation, requires an animal to calculate the probability that a given encounter will result in a threat so they can respond accordingly. Here we review the neural correlates of two highly studied forms of threat response suppression: extinction and safety conditioning. We focus on how relative levels of certainty or uncertainty in the surrounding environment alter the acquisition and application of these processes. We also discuss evidence indicating altered threat response regulation following stress exposure, including enhanced fear conditioning, and disrupted extinction and safety conditioning. To conclude, we discuss research using an animal model of coping that examines the impact of stressor controllability on threat responding, highlighting the potential for previous experiences with control, or other forms of coping, to protect against the effects of future adversity.

Cannabidiol and the corticoraphe circuit in post-traumatic stress disorder

Post-Traumatic Stress Disorder (PTSD), characterized by re-experiencing, avoidance, negative affect, and impaired memory processing, may develop after traumatic events. PTSD is complicated by impaired plasticity and medial prefrontal cortex (mPFC) activity, hyperactivity of the amygdala, and impaired fear extinction. Cannabidiol (CBD) is a promising candidate for treatment due to its multimodal action that enhances plasticity and calms hyperexcitability. CBD’s mechanism in the mPFC of PTSD patients has been explored extensively, but literature on the mechanism in the dorsal raphe nucleus (DRN) is lacking. Following the PRISMA guidelines, we examined current literature regarding CBD in PTSD and overlapping symptomologies to propose a mechanism by which CBD treats PTSD via corticoraphe circuit. Acute CBD inhibits excess 5-HT release from DRN to amygdala and releases anandamide (AEA) onto amygdala inputs. By first reducing amygdala and DRN hyperactivity, CBD begins to ameliorate activity disparity between mPFC and amygdala. Chronic CBD recruits the mPFC, creating harmonious corticoraphe signaling. DRN releases enough 5-HT to ameliorate mPFC hypoactivity, while the mPFC continuously excites DRN 5-HT neurons via glutamate. Meanwhile, AEA regulates corticoraphe activity to stabilize signaling. AEA prevents DRN GABAergic interneurons from inhibiting 5-HT release so the DRN can assist the mPFC in overcoming its hypoactivity. DRN-mediated restoration of mPFC activity underlies CBD’s mechanism on fear extinction and learning of stress coping.

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CBD reduces PTSD symptoms via the DRN and corticoraphe circuit.

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Acute effects of CBD reduce DRN-amygdala excitatory signaling to lessen the activity disparity between amygdala and mPFC.

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Chronic CBD officially resolves mPFC hypoactivity by facilitating 5-HT release from DRN to mPFC.

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CBD-facilitated endocannabinoid signaling stabilizes DRN activity and restores mPFC inhibitory control.

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Chronically administered CBD acts via the corticoraphe circuit to favor fear extinction over fear memory reconsolidation.

Evolution of stress responses refine mechanisms of social rank

Social rank functions to facilitate coping responses to socially stressful situations and conditions. The evolution of social status appears to be inseparably connected to the evolution of stress. Stress, aggression, reward, and decision-making neurocircuitries overlap and interact to produce status-linked relationships, which are common among both male and female populations. Behavioral consequences stemming from social status and rank relationships are molded by aggressive interactions, which are inherently stressful. It seems likely that the balance of regulatory elements in pro- and anti-stress neurocircuitries results in rapid but brief stress responses that are advantageous to social dominance. These systems further produce, in coordination with reward and aggression circuitries, rapid adaptive responding during opportunities that arise to acquire food, mates, perch sites, territorial space, shelter and other resources. Rapid acquisition of resources and aggressive postures produces dominant individuals, who temporarily have distinct fitness advantages. For these reasons also, change in social status can occur rapidly. Social subordination results in slower and more chronic neural and endocrine reactions, a suite of unique defensive behaviors, and an increased propensity for anxious and depressive behavior and affect. These two behavioral phenotypes are but distinct ends of a spectrum, however, they may give us insights into the troubling mechanisms underlying the myriad of stress-related disorders to which they appear to be evolutionarily linked.

Assessing the relationship between the human learned helplessness depression model and anhedonia

The learned helplessness (LH) model is one of the most commonly used acute stress models to explain depression and it has shown good face and predictive validity. However, despite being able to induce depressed-like behaviors and corresponding psychophysiological changes, there is little evidence showing that the LH paradigm can produce anhedonia, a core symptom seen in all forms of depression in humans. So far a couple of studies showed that rodents bred for helplessness develop anhedonic-like behaviors in response to stress; yet, to the best of our knowledge, no similar human research has tried to investigate the direct relationship between the LH model and anhedonia. In the present study, we use a modified version of the original LH task to experimentally and temporarily induce learned helplessness in college students and then examine if the human LH paradigm induces anhedonia. We aim to 1: address the ill-defined connection between the LH model and anhedonia, and 2: directly assess helplessness in humans as opposed to the majority of non-human animal subjects used in the helplessness literature. We believe that our study will fill an important gap in the learned helplessness model literature, and will advance our understanding of the relationship between depression and perceived control, as well as place limitations to what can and cannot be inferred from non-human animal data in this topic.

Sex-specific effects of social defeat stress on miRNA expression in the anterior BNST

Women are more likely to suffer from stress-related affective disorders than men, but the underlying mechanisms of sex differences remain unclear. Previous works show that microRNA (miRNA) profiles are altered in stressed animals and patients with depression and anxiety disorders. In this study, we investigated how miRNA expression in the anterior bed nucleus of stria terminalis (BNST) was affected by social defeat stress in female and male California mice (Peromyscus californicus). We performed sequencing to identify miRNA transcripts in the whole brain and anterior BNST followed by qPCR analysis to compare miRNA expression between control and stressed animals. The results showed that social defeat stress induced sex-specific miRNA expression changes in the anterior BNST. Let-7a, let-7f and miR-181a-5p were upregulated in stressed female but not male mice. Our study provided evidence that social stress produces distinct molecular responses in the BNST of males and females.

Animal models for the study of depressive disorder

Depressive disorder is one of the most widespread forms of psychiatric pathology, worldwide. According to a report by the World Health Organization, the number of people with depression, globally, is increasing dramatically with each year. Previous studies have demonstrated that various factors, including genetics and environmental stress, contribute to the risk of depression. As such, it is crucial to develop a detailed understanding of the pathogenesis of depressive disorder and animal studies are essential for identifying the mechanisms and genetic disorders underlying depression. Recently, many researchers have reported on the pathology of depression via various models of depressive disorder. Given that different animal models of depression show differences in terms of patterns of depressive behavior and pathology, the comparison between depressive animal models is necessary for progress in the field of the depression study. However, the various animal models of depression have not been fully compared or evaluated until now. In this paper, we reviewed the pathophysiology of the depressive disorder and its current animal models with the analysis of their transcriptomic profiles. We provide insights for selecting different animal models for the study of depression.

Patients Living With Breast Cancer During the Coronavirus Pandemic: The Role of Family Resilience, Coping Flexibility, and Locus of Control on Affective Responses

The coronavirus disease 2019 (COVID-19) pandemic has strongly affected oncology patients. Many screening and treatment programs have been postponed or canceled, and such patients also experience fear of increased risk of exposure to the virus. In many cases, locus of control, coping flexibility, and perception of a supportive environment, specifically family resilience, can allow for positive emotional outcomes for individuals managing complex health conditions like cancer. This study aims to determine if family resilience, coping flexibility, and locus of control can mitigate the negative affect caused by the pandemic and enhance positive affect in breast cancer patients. One hundred and fifty-four female patients with breast cancer completed the Walsh’s Family Resilience Questionnaire, the Perceived Ability to Cope With Trauma Scale, the Positive-Negative Affect Schedule, and the Mini Locus of Control Scale. Family resilience and internality of locus of control contribute significantly to positive affective responses. Family resilience is responsible for mitigating the negative affect perceived during the pandemic and is enhanced by external locus of control. Evidence suggests that clinical psychologists should develop and propose programs to support oncology patients’ family resilience, coping flexibility, and internal locus of control, allowing for decreased stress and improved adaptability for effectively managing cancer treatment during the pandemic.

Relationship between depression and olfactory sensory function: a review

Links between olfactory sensory function and effect have been well established. A robust literature exists in both humans and animals showing that disrupting olfaction sensory function can elicit disordered mood state, including serve as a model of depression. Despite this, considerably less is known regarding the directionality and neural basis of this relationship, e.g. whether disruptions in sensory function precede and contribute to altered mood or if altered mood state precipitates changes in olfactory perception. Further, the neural basis of altered olfactory function in depression remains unclear. In conjunction with clinical studies, animal models represent a valuable tool to understand the relationship between altered mood and olfactory sensory function. Here, we review the relevant literature assessing olfactory performance in depression in humans and in rodent models of depressive-like behavioral states. Rodents allow for detailed characterization of alterations in olfactory perception, manipulation of experiential events that elicit depressive-like phenotypes, and allow for interrogation of potential predictive markers of disease and the cellular basis of olfactory impairments associated with depressive-like phenotypes. We synthesize these findings to identify paths forward to investigate and understand the complex interplay between depression and olfactory sensory function.

Characterization of Comorbid Posttraumatic Stress Disorder and Major Depressive Disorder Using Ketamine as an Experimental Medicine Probe

Comorbid posttraumatic stress disorder and major depressive disorder (PTSD + MDD) is the most common pathological response to trauma, yet despite their synergistic detriment to health, knowledge regarding the neurobiological mechanism underlying PTSD + MDD is extremely limited. This study proposes a novel model of PTSD + MDD that is built on biological systems shown to underlay PTSD + MDD and takes advantage of ketamine’s unique suitability to probe PTSD + MDD due to its rescue of stress-related neuroplasticity deficits. The central hypothesis is that changes in PTSD + MDD clinical symptoms are associated with functional connectivity changes and cognitive dysfunction and that ketamine infusions improve clinical symptoms by correction of functional connectivity changes and improvement in cognition. Participants with PTSD + MDD (n = 42) will be randomized to receive a series of six ketamine infusions or saline-placebo over three weeks. Pre/post-measures will include: (1) neuroimaging; (2) cognitive functioning task performance; and (3) PTSD, MDD, and rumination self-report measures. These measures will also be collected once in a trauma-exposed group including PTSD-only (n = 10), trauma-exposed-MDD (TE-MDD; n = 10), and healthy controls (HC, n = 21). Successful completion of the study will strongly support the concept of a biologically-based model of PTSD + MDD. The results will (1) identify functional imaging signatures of the mechanisms underpinning pathological responses to trauma, (2) shift focus from mono-diagnostic silos to unified biological and behavioral disease processes and, thus, (3) inform interventions to correct dysregulation of PTSD + MDD symptom clusters thereby supporting more precise treatments and better outcomes.

Factors Affecting Posttraumatic Stress Disorder in South Korean Trauma Nurses

Trauma nurses are exposed to suffering, death and dying, and vicarious trauma, which may result in nurses experiencing posttraumatic stress disorder (PTSD). This study aims to investigate the extent of PTSD and the effect of the frequency of traumatic events, coping strategies, and social support on PTSD in South Korean trauma nurses. A cross-sectional study was conducted. Participants were 145 trauma nurses recruited from 6 regional trauma centers in Korea. The data were collected through convenience sampling using self-administered questionnaires, including the Korean version of Impact of Event Scale-Revised (IES-R-K), the frequency of traumatic events, coping strategies, and social support. The data were analyzed with descriptive statistics, t test, analysis of variance, Pearson's correlation coefficients, and multiple linear regression. The prevalence of IES-R-K score of 25 or more (indicating a high risk of PTSD) was detected in 57.2% of the trauma nurses. The frequency of traumatic events, work at traumatic emergency units, dysfunctional coping, emotion-focused coping, and social support were found to be significantly associated with PTSD. Therefore, it is necessary to develop PTSD management programs in order to provide effective coping strategies and social support for relieving PTSD symptoms. At the same time, efforts to improve the working environment are needed.

Prefrontal cortex circuits in depression and anxiety: contribution of discrete neuronal populations and target regions

Our understanding of depression and its treatment has advanced with the advent of ketamine as a rapid-acting antidepressant and the development and refinement of tools capable of selectively altering the activity of populations of neuronal subtypes. This work has resulted in a paradigm shift away from dysregulation of single neurotransmitter systems in depression towards circuit level abnormalities impacting function across multiple brain regions and neurotransmitter systems. Studies on the features of circuit level abnormalities demonstrate structural changes within the prefrontal cortex (PFC) and functional changes in its communication with distal brain structures. Treatments that impact the activity of brain regions, such as transcranial magnetic stimulation or rapid-acting antidepressants like ketamine, appear to reverse depression associated circuit abnormalities though the mechanisms underlying the reversal, as well as development of these abnormalities remains unclear. Recently developed optogenetic and chemogenetic tools that allow high-fidelity control of neuronal activity in preclinical models have begun to elucidate the contributions of the PFC and its circuitry to depression- and anxiety-like behavior. These tools offer unprecedented access to specific circuits and neuronal subpopulations that promise to offer a refined view of the circuit mechanisms surrounding depression and potential mechanistic targets for development and reversal of depression associated circuit abnormalities.

Stress-Induced Alteration in Chloride Transporters in the Trigeminal Nerve May Explain the Comorbidity between Depression and Migraine

Migraine is frequently comorbid with depression and anxiety disorders. In the case of depression and panic disorder, the associations seem to be bidirectional. Stress (activation of the hypothalamic-pituitary-adrenal axis) is thought to be involved in increasing the attack frequency. In the current review, it is argued that elevated levels of cortisol increase the function of chloride-ion transporter NKCC1 and decrease the function of chloride-extruder KCC2 in the trigeminal nerve. This leads to a diminished inhibitory effect of gamma-aminobutyric acid (GABA) and an enhanced likelihood of a migraine attack. Since migraine attacks themselves are stressful, and since brain areas are activated that could contribute to panic, anxiety and depression, a number of self-sustaining circular processes could occur that would explain the bi-directionality of the associations. On the basis of this hypothesis, several novel therapeutic approaches to counter the pathological process can be proposed. These include inhibition of corticotrophin releasing factor by CRF1 receptor antagonists, blockade of adrenocorticotropic hormone (ACTH) at the MC2 receptor, and inhibition of the hyperactive NKCC1 chloride-transporter.

Combinatorial Effects of Discrimination, Legal Status Fears, Adverse Childhood Experiences, and Harsh Working Conditions among Latino Migrant Farmworkers: Testing Learned Helplessness Hypotheses

Migrant farmwork is often characterized by harsh working conditions that carry significant physical and mental health consequences. Using a learned helplessness framework, the current study examined the extent to which discrimination, immigration legal status difficulties, and adverse childhood experiences moderated the effects of harsh working conditions on depression and anxiety. The study also examined the extent to which harsh working conditions mediated the effects of discrimination, immigration legal status difficulties, and adverse childhood experiences on depression and anxiety. Participants were 241 migrant farmworkers recruited in the Midwest. Participants completed interviews consisting of the Migrant Farmworker Stress Index (MFWSI), Adverse Childhood Events scale (ACEs), Everyday Discrimination Scale, the Centers for Epidemiology Scale for Depression (CES-D), and the seven item Generalized Anxiety Disorder scale (GAD-7). Tests of indirect effects suggested, working conditions mediated the effects of ACEs, immigration legal status fears, and discrimination on CES-D and GAD-7 scores (p-values < .05). Higher ACEs and discrimination also appeared to be associated with larger effects of harsh working conditions on depression and anxiety (p-values < .05), while legal status fears did not significantly moderate the effect of harsh working conditions on either outcome (p-values > .05). Likely through different mechanisms, adverse childhood experiences, discrimination and immigration legal status are associated with higher risk of harsh working conditions and subsequently these conditions account for much of the relations between these three stressors with depression and anxiety. Additionally, discrimination and adverse childhood experiences appear to then enhance the effects of working conditions.

Chemogenetic activation of an infralimbic cortex to basolateral amygdala projection promotes resistance to acute social defeat stress

Tremendous individual differences exist in stress responsivity and social defeat stress is a key approach for identifying cellular mechanisms of stress susceptibility and resilience. Syrian hamsters show reliable territorial aggression, but after social defeat they exhibit a conditioned defeat (CD) response characterized by increased submission and an absence of aggression in future social interactions. Hamsters that achieve social dominance prior to social defeat exhibit greater defeat-induced neural activity in infralimbic (IL) cortex neurons that project to the basolateral amygdala (BLA) and reduced CD response compared to subordinate hamsters. Here, we hypothesize that chemogenetic activation of an IL-to-BLA neural projection during acute social defeat will reduce the CD response in subordinate hamsters and thereby produce dominant-like behavior. We confirmed that clozapine-N-oxide (CNO) itself did not alter the CD response and validated a dual-virus, Cre-dependent, chemogenetic approach by showing that CNO treatment increased c-Fos expression in the IL and decreased it in the BLA. We found that CNO treatment during social defeat reduced the acquisition of CD in subordinate, but not dominant, hamsters. This project extends our understanding of the neural circuits underlying resistance to acute social stress, which is an important step toward delineating circuit-based approaches for the treatment of stress-related psychopathologies.

Corticotropin-Releasing Factor Receptors in the Locus Coeruleus Modulate the Enhancement of Active Coping Behaviors Induced by Chronic Predator Odor Inoculation in Mice

Stress inoculation has been proved to induce active coping behaviors to subsequent stress. However, the specific neural mechanisms underlying this effect remain unclear. In this study, a chronic and mild predator odor exposure model was established to investigate the effect of predator odor stress inoculation on behaviors in novel predator odor exposure, open field test and forced swimming test (FST), and on the expression of CRF receptors in locus coeruleus (LC) and dorsal raphe nuclei (DRN). The results showed that predator odor stress inoculation increased the active coping of mice under the severe stress environment without changing the stress response to a new predator odor. Meanwhile, in LC, the CRFR1 expression was increased by predator odor stress inoculation. These results suggested that predator odor stress inoculation can be used as an effective training method to improve active response to later severe stress and the function of CRFR1 in LC might be a potential underlying biological mechanism.

The Bed Nucleus of the Stria Terminalis as a Brain Correlate of Psychological Inflexibility in Fibromyalgia

This study explored the brain structural correlates of psychological flexibility (PF) as measured with the Psychological Inflexibility in Pain Scale (PIPS) in patients with fibromyalgia (FM). Structural magnetic resonance imaging data from 47 FM patients were used to identify Gray Matter Volume (GMV) alterations related to PIPS scores. Brain GMV clusters related to PIPS were then correlated with clinical and cognitive variables to further explore how emerged brain clusters were intertwined with FM symptomatology. Longitudinal changes in PIPS-related brain clusters values were assessed by studying pre–post data from 30 patients (15 allocated to a mindfulness-based stress reduction (MBSR) program and 15 to treatment-as-usual). Changes in PIPS-related brain clusters were also explored in participants showing greater/lower longitudinal changes in PIPS scores. PIPS scores were positively associated with GMV in a bilateral cluster in the ventral part of the bed nucleus of the stria terminalis (BNST). Significant associations between BNST cluster with functional impairment, depressive symptomatology, perceived stress and the nonjudging mindfulness facet were observed. Participants reporting greater pre–post increases in PIPS scores showed greater increases in BNST cluster values. These findings contribute to the understanding on the neurobiological bases of PF in FM and encourage further explorations of the role of the BNST in chronic pain.

Threat imminence dictates the role of the bed nucleus of the stria terminalis in contextual fear

Recent work indicates that the bed nucleus of the stria terminalis (BNST) is critically involved in the regulation of conditioned fear responses to unpredictable threats. Here we examined whether the involvement of the BNST in contextual fear conditioning in male rats depends on the imminence of shock after placement in the conditioning chamber. Specifically, we hypothesized that the BNST supports contextual freezing after conditioning with delayed, but not imminent, footshock (relative to placement in the context). Rats were implanted with cannulae targeting the BNST and underwent a contextual fear conditioning procedure in which a single footshock unconditioned stimulus (US) was delivered either 1 min or 9 min after the rat was placed in the context; the rats received a total of four identical conditioning sessions over two days, all with equivalent exposure to the context. Contexts associated with either imminent or delayed US onsets produced distinct patterns of freezing and shock-induced activity but freezing in each case was context-dependent. Reversible inactivation of the BNST reduced the expression of contextual freezing in the context paired with delayed (9 min), but not imminent (1 min), footshock onset. Implications of these data are discussed in the light of recent conceptualizations of BNST function, as well as for anxiety behaviors.

Subjective Uncontrollability over Aversive Events Reduces Working Memory Performance and Related Large-Scale Network Interactions

Lack of control over significant events may induce a state of learned helplessness that is characterized by cognitive, motivational, and affective deficits. Although highly relevant in the pathogenesis of several mental disorders, the extent of the cognitive deficits induced by experiences of uncontrollability and the neural mechanisms underlying such deficits in humans remain poorly understood. Using functional magnetic resonance imaging (fMRI), we tested here whether uncontrollability over aversive events impairs subsequent working memory performance and, if so, which neural processes are involved in such deficits. We assessed working memory and the involved neurocircuitry in the MRI scanner before and after participants underwent a task in which they could either learn to avoid electric shocks or had no instrumental control over shocks. Our results show that subjective, but not objective, uncontrollability over aversive events impaired working memory performance. This impact of subjective uncontrollability was linked to altered prefrontal and parahippocampal activities and connectivity as well as decreased crosstalk between frontoparietal executive and salience networks. Our findings show that the perceived uncontrollability over aversive events, rather than the aversive events themselves or the actual, objective control over them, disrupts subsequent working memory processes, most likely through altered crosstalk between prefrontal, temporal, and parietal areas.

Psychiatric comorbidity and co-occurring opioid misuse: Depression mediates the relationship between post-traumatic stress disorder and opioid misuse in community pharmacy settings

AbstractsBackground: Individuals who misuse opioids frequently have comorbid psychiatric issues, including post-traumatic stress disorder (PTSD) and depression. However, little is known about the mechanisms by which these disorders are associated with opioid misuse and specifically in community pharmacy settings. The current study examined whether depression mediated the relationship between PTSD and opioid misuse in patients filling opioid prescriptions. Methods: We administered a health survey in four community pharmacies among patients filling opioid medications in southwestern Pennsylvania. Univariate statistics were used to assess relationships among demographic and clinical characteristics of PTSD, depression, and opioid misuse behaviors. We then examined whether depression mediated the relationship between PTSD and opioid misuse using ordinary least squares path analysis with bootstrapping. Results: A total of 333 participants completed the health survey. Opioid misuse was reported among 15.9% of all participants, 33.3% among those with a positive PTSD screen, and 29.3% of those who screened positive for depression. Depression significantly mediated the relationship between PTSD and opioid misuse. Specifically, there was a statistically significant indirect effect (ab) of PTSD on opioid misuse through a pathway mediated by depression (ab = .06, SE_ab = .02, 95% CI = .02-.10). The direct effect (c') of PTSD on opioid misuse was also significant (c' = .12, SE_c' = .05, P = .01, 95% CI = .03-.22), suggesting partial mediation. Conclusions: Results suggest an indirect pathway by which clinical intervention may help ameliorate outcomes in patients with PTSD. Further, there is an increased need for screening, assessment, and intervention protocols for this patient population in which community pharmacy is a novel setting to expand future efforts within the patient population.

Reframing PTSD for computational psychiatry with the active inference framework

Introduction: Recent advances in research on stress and, respectively, on disorders of perception, learning, and behaviour speak to a promising synthesis of current insights from (i) neurobiology, cognitive neuroscience and psychology of stress and post-traumatic stress disorder (PTSD), and (ii) computational psychiatry approaches to pathophysiology (e.g. of schizophrenia and autism). Methods: Specifically, we apply this synthesis to PTSD. The framework of active inference offers an embodied and embedded lens through which to understand neuronal mechanisms, structures, and processes of cognitive function and dysfunction. In turn, this offers an explanatory model of how healthy mental functioning can go awry due to psychopathological conditions that impair inference about our environment and our bodies. In this context, auditory phenomena-known to be especially relevant to studies of PTSD and schizophrenia-and traditional models of auditory function can be viewed from an evolutionary perspective based on active inference. Results: We assess and contextualise a range of evidence on audition, stress, psychosis, and PTSD, and bring some existing partial models of PTSD into multilevel alignment. Conclusions: The novel perspective on PTSD we present aims to serve as a basis for new experimental designs and therapeutic interventions that integrate fundamentally biological, cognitive, behavioural, and environmental factors.

Dissociation in Effective Treatment and Behavioral Phenotype Between Stress-Enhanced Fear Learning and Learned Helplessness

Post-traumatic stress disorder (PTSD) is a debilitating disease with relatively high lifetime prevalence. It is marked by a high diversity of symptoms and comorbidity with other psychiatric disease. Furthermore, PTSD has a high level of origin and symptom heterogeneity within the population. These characteristics taken together make it one of the most challenging diseases to effectively model in animals. However, with relatively little headway made in developing effective disease interventions, PTSD remains as a high priority target for animal model study. Learned Helplessness (LH) is a procedure classically used to model depression, but has in recent years transitioned to use as a model of PTSD. Animals in this procedure receive 100 inescapable and unpredictable tailshocks or simple restraint without shock. The following day, the animals are tested in a shuttle box, where inescapably-shocked subjects exhibit exaggerated fear and profound deficit in escape performance. Stress-enhanced fear learning (SEFL) also uses an acute (single session) stressor for modeling PTSD in rodents. The SEFL procedure begins with exposure to 15 footshocks or simple context exposure without shock. Animals that initially received the 15 footshocks exhibit future enhanced fear learning. In this review, we will compare the behavior, physiology, and interventions of these two animal models of PTSD. Despite considerable similarity (a single session containing inescapable and uncontrollable shock) the two procedures produce a very divergent set of behavioral consequences.

Role of the Bed Nucleus of the Stria Terminalis in PTSD: Insights From Preclinical Models

Post-traumatic stress disorder (PTSD) afflicts approximately 8% of the United States population and represents a significant public health burden, but the underlying neural mechanisms of this and other anxiety- and stressor-related disorders are largely unknown. Within the last few decades, several preclinical models of PSTD have been developed to help elucidate the mechanisms underlying dysregulated fear states. One brain area that has emerged as a critical mediator of stress-related behavioral processing in both clinical and laboratory settings is the bed nucleus of the stria terminalis (BNST). The BNST is interconnected with essential emotional processing regions, including prefrontal cortex, hippocampus and amygdala. It is activated by stressor exposure and undergoes neurochemical and morphological alterations as a result of stressor exposure. Stress-related neuro-peptides including corticotropin-releasing factor (CRF) and pituitary adenylate cyclase activating peptide (PACAP) are also abundant in the BNST, further implicating an involvement of BNST in stress responses. Behaviorally, the BNST is critical for acquisition and expression of fear and is well positioned to regulate fear relapse after periods of extinction. Here, we consider the role of the BNST in stress and memory processes in the context of preclinical models of PTSD.

Alterations and adaptation of ventral tegmental area dopaminergic neurons in animal models of depression

Depression is one of the most prevalent psychiatric diseases, affecting the quality of life of millions of people. Ventral tegmental area (VTA) dopaminergic (DA) neurons are notably involved in evaluating the emotional and motivational value of a stimulus, in detecting reward prediction errors, in motivated learning, or in the propensity to initiate or withhold an action. DA neurons are thus involved in psychopathologies associated with perturbations of emotional and motivational states, such as depression. In this review, we focus on adaptations/alterations of the VTA, particularly of the VTA DA neurons, in the three most frequently used animal models of depression: learned helplessness, chronic mild stress and chronic social defeat.

Modelling posttraumatic stress disorders in animals

Animal models of posttraumatic stress disorder are useful tools to reveal the neurobiological basis of the vulnerability to traumatic events, and to develop new treatment strategies, as well as predicting treatment response contributing to personalized medicine approach. Different models have different construct, face and predictive validity and they model different symptoms of the disease. The most prevalent models are the single prolonged stress, electric foot-shock and predator odor. Freezing as 're-experiencing' in cluster B and startle as 'arousal' in cluster E according to DSM-5 are the most frequently studied parameters; however, several other symptoms related to mood, cognitive and social skills are part of the examinations. Beside behavioral characteristics, symptoms of exaggerated sympathetic activity and hypothalamic-pituitary-adrenocortical axis as well as signs of sleep disturbances are also warranted. Test battery rather than a single test is required to describe a model properly and the results should be interpreted in a comprehensive way, e.g. creating a z-score. Research is shifting to study larger populations and identifying the features of the resilient and vulnerable individuals, which cannot be easily done in humans. Incorporation of the "three hit theory" in animal models may lead to a better animal model of vulnerability and resilience. As women are twice as vulnerable as men, more emphasize should be taken to include female animals. Moreover, hypothesis free testing and big data analysis may help to identify an array of biomarkers instead of a single variable for identification of vulnerability and for the purpose of personalized medicine.

Evidence that preimmunization with a heat-killed preparation of Mycobacterium vaccae reduces corticotropin-releasing hormone mRNA expression in the extended amygdala in a fear-potentiated startle paradigm

Posttraumatic stress disorder (PTSD) is a trauma and stressor-related disorder that is characterized by dysregulation of glucocorticoid signaling, chronic low-grade inflammation, and impairment in the ability to extinguish learned fear. Corticotropin-releasing hormone (Crh) is a stress- and immune-responsive neuropeptide secreted from the paraventricular nucleus of the hypothalamus (PVN) to stimulate the hypothalamic-pituitary-adrenal (HPA) axis; however, extra-hypothalamic sources of Crh from the central nucleus of the amygdala (CeA) and bed nucleus of the stria terminalis (BNST) govern specific fear- and anxiety-related defensive behavioral responses. We previously reported that preimmunization with a heat-killed preparation of the immunoregulatory environmental bacterium Mycobacterium vaccae NCTC 11659 enhances fear extinction in a fear-potentiated startle (FPS) paradigm. In this follow-up study, we utilized an in situ hybridization histochemistry technique to investigate Crh, Crhr1, and Crhr2 mRNA expression in the CeA, BNST, and PVN of the same rats from the original study [Fox et al., 2017, Brain, Behavior, and Immunity, 66: 70-84]. Here, we demonstrate that preimmunization with M. vaccae NCTC 11659 decreases Crh mRNA expression in the CeA and BNST of rats exposed to the FPS paradigm, and, further, that Crh mRNA expression in these regions is correlated with fear behavior during extinction training. These data are consistent with the hypothesis that M. vaccae promotes stress-resilience by attenuating Crh production in fear- and anxiety-related circuits. These data suggest that immunization with M. vaccae may be an effective strategy for prevention of fear- and anxiety-related disorders.

Post-Stress Fructose and Glucose Ingestion Exhibit Dissociable Behavioral and Physiological Effects

An acute traumatic event can lead to lifelong changes in stress susceptibility and result in psychiatric disease such as Post-Traumatic Stress Disorder (PTSD). We have previously shown that access to a concentrated glucose solution for 24 hours beginning immediately after trauma decreased stress-related pathology in the learned helplessness model of PTSD and comorbid major depression. The current study sought to investigate the peripheral physiological effects of post-stress glucose consumption. We exposed 128 male Sprague-Dawley rats to inescapable and unpredictable 1-milliamp electric tail shocks or simple restraint in the learned helplessness procedure. Rats in each stress condition had access to a 40% glucose solution, 40% fructose solution, or water. Blood and liver tissue were extracted and processed for assay. We assessed corticosterone, corticosteroid-binding globulin (CBG), glucose, and liver glycogen concentrations at various time points following stress. We found that rats given access to glucose following exposure to traumatic shock showed a transient rise in blood glucose and an increase in liver glycogen repletion compared to those that received water or fructose following exposure to electric shock. We also found that animals given glucose following shock exhibited reduced free corticosterone and increased CBG compared to their water-drinking counterparts. However, this difference was not apparent when glucose was compared to fructose. These data suggest that post-stress glucose prophylaxis is likely not working via modulation of the HPA axis, but rather may provide its benefit by mitigating the metabolic challenges of trauma exposure.

Sex-associated differences in excitability within the bed nucleus of the stria terminalis are reflective of cell-type

The bed nucleus of the stria terminalis (BNST) is a sexually dimorphic brain region which plays a key role in stress, anxiety, and anxiety-related disorders. Human females have an increased susceptibility to anxiety-related disorders, however the physiological basis of this is not fully understood. Here we examined the effect of the oestrous cycle and sex on the electrophysiological properties of Type I and Type II cells in the anterolateral area of the BNST (BNSTALG) in unstressed animals. There was no significant effect of oestrous cycle on any of the parameters examined in either cell type. Compared to males, the female cohort had lower capacitance in Type I cells while having a higher capacitance in Type II cells. Type II cells also displayed decreased excitability in the female cohort. In order to confirm the effect of these populations on stress and anxiety, a correlation with behaviour on the elevated zero maze was carried out. We observed that increased excitability in Type II neurons correlated with a decrease in anxiety-like behaviour. These sex-specific differences in excitability may contribute to altered susceptibility to anxiety-related disorders.

Dysregulation of the Lateral Habenula in Major Depressive Disorder

Clinical and preclinical evidence implicates hyperexcitability of the lateral habenula (LHb) in the development of psychiatric disorders including major depressive disorder (MDD). This discrete epithalamic nucleus acts as a relay hub linking forebrain limbic structures with midbrain aminergic centers. Central to reward processing, learning and goal directed behavior, the LHb has emerged as a critical regulator of the behaviors that are impaired in depression. Stress-induced activation of the LHb produces depressive- and anxiety-like behaviors, anhedonia and aversion in preclinical studies. Moreover, deep brain stimulation of the LHb in humans has been shown to alleviate chronic unremitting depression in treatment resistant depression. The diverse neurochemical processes arising in the LHb that underscore the emergence and treatment of MDD are considered in this review, including recent optogenetic studies that probe the anatomical connections of the LHb.

"If One Does Not Fulfil His Duties, He Must Not Be a Man": Masculinity, Mental Health and Resilience Amongst Sri Lankan Tamil Refugee Men in Canada

Refugee men face unique mental health stressors in the pre- and post-migratory periods. However, there has been little in-depth research on the mental health of refugee men in Canada. Given this situation, the overall aim of this study is to explore the psycho-social experience of Sri Lankan Tamil refugee men in Canada. Particular objectives include better understanding any inter-relationship between war-trauma, migration, concepts of masculinity and mental health. The study employed a two-phase participatory action research design based on the grounded theory approach. Phase 1 involved an 8-month ethnography conducted in Sri Lanka. Phase 2 consisted of qualitative interviews with 33 Sri Lankan Tamil refugee men living in Canada. Consistent with grounded theory, analysis was conducted inductively and iteratively. Four specific themes emerged from the data (i) gendered helplessness of war: participants commonly reported ongoing negative rumination regarding experiences where they were unable to adequately protect loved ones from physical suffering or death; (ii) reduced capacity: participants frequently felt unable to fulfill culturally sanctioned duties, such as supporting their family, due to ongoing pre- and post-migratory stress; (iii) redundancy: many participants felt that they were useless in Canada, as they could not fulfill typical masculine social roles (e.g. provider) due to factors such as unemployment and underemployment; (iv) intimate criticism: some participants reported that their spouses would often attempt to 'shame' them into greater achievement by constantly reminding them of their 'failures'. Many found this distressing. These various failures culminated in a state that we label "depleted masculinity", which participants linked to emotional and behavioural problems. Participants reported that they actively tried to rebuild their masculine identity, for example by adopting leadership roles in community organizations, which fostered resiliency. Results suggest a need to review and rebuild masculine identity to support the mental health of refugee men.

Activation of kappa opioid receptors in the dorsal raphe have sex dependent effects on social behavior in California mice

Kappa opioid receptor activation has been linked to stress and anxiety behavior, thus leading to kappa antagonists being popularized in research as potential anxiolytics. However, while these findings may hold true in standard models, the neuromodulatory effects of social defeat may change the behavioral outcome of kappa opioid receptor activation. Previous research has shown that social defeat can lead to hyperactivity of serotonergic neurons in the dorsal raphe nucleus, and that inhibition of this increase blocks the social deficits caused by defeat. Kappa opioid receptor activation in the dorsal raphe nucleus works to decrease serotonergic activity. We injected the kappa opioid receptor U50,488 directly into the dorsal raphe nucleus of male and female, defeat and control adult California mice. Here we show evidence that U50,488 induces anxiety behavior in control male California mice, but helps relieve it in defeated males. Consistent with previous literature, we find little effect in females adding evidence that there are marked and important sex differences in the kappa opioid system.

Pituitary Adenylate Cyclase-Activating Peptide (PACAP) Signaling and the Dark Side of Addiction

While addiction to drugs of abuse represents a significant health problem worldwide, the behavioral and neural mechanisms that underlie addiction and relapse are largely unclear. The concept of the dark side of addiction, developed and explored by George Koob and colleagues, describes a systematic decrease in reward-related processing following drug self-administration and subsequent recruitment of anti-reward (i.e., stress) systems. Indeed, the activation of central nervous system (CNS) stress-response systems by drugs of abuse is contributory not only to mood and anxiety-related disorders but critical to both the maintenance of addiction and relapse following abstinence. In both human and animal studies, compounds that activate the bed nucleus of the stria terminalis (BNST) have roles in stress-related behaviors and addiction processes. The activation of pituitary adenylate cyclase-activating peptide (PACAP) systems in the BNST mediates many consequences of chronic stressor exposure that may engage in part downstream corticotropin-releasing hormone (CRH) signaling. Similar to footshock stress, the BNST administration of PACAP or the PAC1 receptor-specific agonist maxadilan can facilitate relapse following extinction of cocaine-seeking behavior. Further, in the same paradigm, the footshock-induced relapse could be attenuated following BNST pretreatment with PAC1 receptor antagonist PACAP6-38, implicating PACAP systems as critical components underlying stress-induced reinstatement. In congruence with previous work, the PAC1 receptor internalization and endosomal MEK/ERK signaling appear contributory mechanisms to the addiction processes. The studies offer new insights and approaches to addiction and relapse therapeutics.