Amygdala-dependent fear is regulated by Oprl1 in mice and humans with PTSD

Stress-induced changes in the molecular processes underlying fear memories: implications for PTSD and relevant animal models

Most of the fear literature on humans and animals tests healthy individuals. However, fear memories can differ between healthy individuals and those previously exposed to traumatic stress, such as a car accident, sexual abuse, military combat and personal assault. Traumatic stress can lead to post-traumatic stress disorder (PTSD) which presents alterations in fear memories, such as an impairment of fear extinction and extinction recall. PTSD-like animal models are exposed to a single highly stressful experience in the laboratory, such as stress immobilization or single-prolonged stress. Some days later, animals exposed to a PTSD-like model can be tested in fear procedures that help uncover molecular mechanisms of fear memories. In this review, there are discussed the molecular mechanisms in stress-induced fear memories of patients with PTSD and PTSD-like animal models. The focus is on the effects of estradiol and cortisol/corticosterone hormones and of different genes, such as FKBP prolyl isomerase 5 gene (FKBP5) - FK506 binding protein 51 (FKBP51), pituitary adenylate cyclase-activating peptide (PACAP) - pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1R), endocannabinoid (eCB) system and the tropomyosin receptor kinase B (TrkB) - brain-derived neurotrophic factor (BDNF). The conclusion is that greater emphasis should be placed on investigating the molecular mechanisms of fear memories in PTSD, through direct testing of patients with PTSD or the use of relevant PTSD-like models.

Genetic and Environmental Influences on Anxiety Disorders: A Systematic Review of Their Onset and Development

Fear is an emotion most humans feel throughout their lifetime, often without knowing its exact cause. Fear is considered a behavioural act to escape a potentially threatening situation, whereas anxiety is distinguished by the lack of actual stimuli and, more so, the threat of potential stimuli. Fear and anxiety are two distinct emotions which warrant separate classifications. Understanding both the genetic and environmental influences which contribute to anxiety disorder onset and development can aid in prevention, diagnosis and management; it may also play a role in helping patients further understand their diagnosis and guide future research. This review examines genetic and environmental contributions to the onset and development of anxiety disorders and explores their implications for treatments and further research. An extensive search of databases, including PubMed, Web of Science and Google Scholar, using specific search terms led to the collection of a large number of studies prior to further screening. The inclusion criteria were: studies written in English, full-text available, human studies, and studies conducted within the last 10 years (at the time of writing). The exclusion criteria were: animal studies, studies with a focus on neurological anatomy rather than anxiety disorders, and studies including depressive or other psychological disorders. Using a cross-sectional approach allowed for the strengths to be summarised whilst considering the limitations of the research. The studies were screened for limitations and some of these were stated within the research, whilst others had to be interpreted using a subset of pre-formulated questions to ensure reproducibility. Variables such as the main outcomes, conclusions and limitations were tabulated to guide the interpretation of these studies. Genetic predispositions were linked to specific gene polymorphisms or familial abnormalities in neurological anatomy and often correlated with the likelihood of the onset of anxiety disorders or contributed to the severity of symptoms. Environmental influences were found to affect the functioning of the brain and some studies established the impacts that therapies have on brain function. The majority of studies have implicated that a combination of genetics and environment have an effect on anxiety disorders, with one study suggesting that a single traumatic event can lead to alterations in the function of specific genes related to anxiety disorders. Both genetic and environmental factors contribute to the onset, development and severity of anxiety disorders, with environmental triggers often influencing the phenotypic expression of these disorders. Further research would benefit from determining specific processes which lead to the onset of anxiety disorders to facilitate their detection and intervention before resulting in life-long and generational consequences. Studies including larger sample sizes and varied subjects would be advantageous in the future.

Pharmacological treatments for co-occurring PTSD and substance use disorders: A systematic review

INTRODUCTION

Post-traumatic stress disorder and substance use disorders commonly co-occur and are associated with worse health outcomes. Currently, only psychosocial therapies are specifically recommended for use in the co-occurring population, but these come with numerous barriers to access and engagement. This study aims to identify potential pharmacological treatments to enhance treatment options and outcomes for this population.

METHODS

This systematic review identified studies on pharmacological treatment of co-occurring PTSD and SUD in humans, using validated outcome measurements, with study design of RCT, observational study, case control study or cohort study.

RESULTS

29 studies were identified for inclusion, looking at a range of 16 pharmacotherapies. A majority concentrated on alcohol use disorders and males, with many focused on the veteran population.

CONCLUSIONS

This is an area for further research, inclusive of more SUDs, genders and civilians. Future studies utilizing consistent dosing, populations and measurement outcomes will allow for future meta-analysis.

Drug repurposing opportunities for breast cancer and seven common subtypes

Breast cancer is a substantial global health problem, and drug repurposing provides novel opportunities to address the urgent need for therapeutics. According to significant Mendelian randomization (MR) results, we identified 26 genes for overall breast cancer, 25 genes for ER+ breast cancer and 4 genes (CASP8, KCNN4, MYLK4, TNNT3) for ER- breast cancer. In order to explore the differences between 5 intrinsic subtypes, we found 29 actionable druggable genes for Luminal A breast cancer, 2 genes (IGF2 and TNNT3) for Luminal B breast cancer, 1 gene (FAAH) for Luminal B HER2 negative breast cancer, and 3 genes (CASP8, KCNN4, and TP53) for triple-negative breast cancer. After colocalization analysis, we determined OPRL1 as a prioritized target in both overall and Luminal A breast cancer. Additionally, FES and FAAH were considered prioritized targets for ER+ breast cancer. Through molecular docking, crizotinib stand out as a prioritized FES target drug repurposing opportunity with the lowest binding energy (-10.13 kJ·mol-1) and CCK-8 assay showed ER+ cell groups were more sensitive to crizotinib than ER- cell groups. In conclusion, OPRL1 was identified as a prioritized target for both overall and Luminal A breast cancer. Moreover, FES and FAAH were recognized as prioritized targets for ER+ breast cancer.

Sex differences in prelimbic cortex calcium dynamics during stress and fear learning

In recent years, research has progressively increased the importance of considering sex differences in stress and fear memory studies. Many studies have traditionally focused on male subjects, potentially overlooking critical differences with females. Emerging evidence suggests that males and females can exhibit distinct behavioral and neurophysiological responses to stress and fear conditioning. These differences may be attributable to variations in hormone levels, brain structure, and neural circuitry, particularly in regions such as the prefrontal cortex (PFC). In the present study, we explored sex differences in prelimbic cortex (PL) calcium activity in animals submitted to immobilization stress (IMO), fear conditioning (FC), and fear extinction (FE). While no significant sex differences were found in behavioral responses, we did observe differences in several PL calcium activity parameters. To determine whether these results were related to behaviors beyond stress and fear memory, we conducted correlation studies between the movement of the animals and PL activity during IMO and freezing behavior during FC and FE. Our findings revealed a clear correlation between PL calcium activity with movement during stress exposure and freezing behavior, with no sex differences observed in these correlations. These results suggest a significant role for the PL in movement and locomotion, in addition to its involvement in fear-related processes. The inclusion of both female and male subjects is crucial for studies like this to fully understand the role of the PFC and other brain areas in stress and fear responses. Recognizing sex differences enhances our comprehension of brain function and can lead to more personalized and effective approaches in the study and treatment of stress and fear-related conditions.

What I was thinking/what I would do differently: Biological markers and mechanisms of mental health

At the 39th meeting of the International Society of Traumatic Stress Studies, four leading scientists and clinicians were invited to reflect on their careers, focusing on the biological mechanisms and markers of traumatic stress. Dr. Raul Andero has contributed to understanding how stress alters memory networks in the brain, influencing the development of novel treatments. Dr. Tanja Jovanovic has pioneered the measurement and mechanistic understanding of fear learning, bridging basic and clinical research. Dr. Murray B. Stein has scaled up clinical and lab observations to large populations, refining the field's understanding of traumatic stress. Dr. Arieh Y Shalev has shaped the definition of traumatic stress, pioneering the longitudinal investigation of stress and integrating advanced computational methods to identify individuals at risk. These panelists were asked to reflect on their initial problems, ambitions, concerns, and unexpected challenges, as well as the influence of their work, on new research trajectories. Their insights provide valuable lessons about the process and content of their work, and their pioneering efforts have significantly advanced our understanding of the biological mechanisms and markers of traumatic stress.

Lithium response in bipolar disorder: Epigenome-wide DNA methylation signatures and epigenetic aging

Lithium (Li) is the first-line treatment for bipolar disorder (BD) even though only 30 % of BD patients are considered excellent responders. The mechanisms by which Li exerts its action are not clearly understood, but it has been suggested that specific epigenetic mechanisms, such as methylation processes, may play a role. In this regard, DNA methylation patterns can be used to estimate epigenetic age (EpiAge), which is accelerated in BD patients and reversed by Li treatment. Our first aim was to compare the DNA methylation profile in peripheral blood between BD patients categorized as excellent responders to Li (Ex-Rp) and non-responders (N-Rp). Secondly, EpiAge was estimated to detect differential age acceleration between the two groups. A total of 130 differentially methylated positions (DMPs) and 16 differentially methylated regions (DMRs) between Ex-Rp (n = 26) and N-Rp (n = 37) were identified (FDR adjusted p-value < 0.05). We found 122 genes mapping the DMPs and DMRs, nine of which (HOXB6, HOXB3, HOXB-AS3, TENM2, CACNA1B, ANK3, EEF2K, CYP1A1, and SORCS2) had previously been linked to Li response. We found genes related to the GSK3β pathway to be highly represented. Using FUMA, we found enrichment in Gene Ontology Cell Component for the synapse. Gene network analysis highlighted functions related to the cell cycle, nervous system development and function, and gene expression. No significant differences in age acceleration were found between Ex-Rp and N-Rp for any of the epigenetic clocks analysed. Our findings indicate that a specific methylation pattern could determine the response to Li in BD patients. We also found that a significant portion of the differentially methylated genes are closely associated with the GSK3β pathway, reinforcing the role of this system in Li response. Future longitudinal studies with larger samples will help to elucidate the epigenetic mechanisms underlying Li response.

Drug repurposing opportunities for chronic kidney disease

The development of targeted drugs for the early prevention and management of chronic kidney disease (CKD) is of great importance. However, the success rates and cost-effectiveness of traditional drug development approaches are extremely low. Utilizing large sample genome-wide association study data for drug repurposing has shown promise in many diseases but has not yet been explored in CKD. Herein, we investigated actionable druggable targets to improve renal function using large-scale Mendelian randomization and colocalization analyses. We combined two population-scale independent genetic datasets and validated findings with cell-type-dependent eQTL data of kidney tubular and glomerular samples. We ultimately prioritized two drug targets, opioid receptor-like 1 and F12, with potential genetic support for restoring renal function and subsequent treatment of CKD. Our findings explore the potential pathological mechanisms of CKD, bridge the gap between the molecular mechanisms of pathogenesis and clinical intervention, and provide new strategies in future clinical trials of CKD.

Targeting Nociceptin/Orphanin FQ receptor to rescue cognitive symptoms in a mouse neuroendocrine model of chronic stress

Chronic stress causes cognitive deficits, such as impairments in episodic-like hippocampus-dependent memory. Stress regulates an opioid-related neuropeptide named Nociceptin/Orphanin FQ (N/OFQ), the ligand of the G protein-coupled receptor NOP. Since this peptide has deleterious effects on memory, we hypothesized that the N/OFQ system could be a mediator of the negative effects of stress on memory. Chronic stress was mimicked by chronic exposure to corticosterone (CORT). The NOP receptor was either acutely blocked using selective antagonists, or knocked-down specifically in the hippocampus using genetic tools. Long-term memory was assessed in the object recognition (OR) and object location (OL) paradigms. Acute injection of NOP antagonists before learning had a negative impact on memory in naive mice whereas it restored memory performances in the chronic stress model. This rescue was associated with a normalization of neuronal cell activity in the CA3 part of the hippocampus. Chronic CORT induced an upregulation of the N/OFQ precursor in the hippocampus. Knock-down of the NOP receptor in the CA3/Dentate Gyrus region prevented memory deficits in the CORT model. These data demonstrate that blocking the N/OFQ system can be beneficial for long-term memory in a neuroendocrine model of chronic stress. We therefore suggest that NOP antagonists could be useful for the treatment of memory deficits in stress-related disorders.

Rats respond to aversive emotional arousal of human handlers with the activation of the basolateral and central amygdala

Reading danger signals may save an animal's life, and learning about threats from others allows avoiding first-hand aversive and often fatal experiences. Fear expressed by other individuals, including those belonging to other species, may indicate the presence of a threat in the environment and is an important social cue. Humans and other animals respond to conspecifics' fear with increased activity of the amygdala, the brain structure crucial for detecting threats and mounting an appropriate response to them. It is unclear, however, whether the cross-species transmission of threat information involves similar mechanisms, e.g., whether animals respond to the aversively induced emotional arousal of humans with activation of fear-processing circuits in the brain. Here, we report that when rats interact with a human caregiver who had recently undergone fear conditioning, they show risk assessment behavior and enhanced amygdala activation. The amygdala response involves its two major parts, the basolateral and central, which detect a threat and orchestrate defensive responses. Further, we show that humans who learn about a threat by observing another aversively aroused human, similar to rats, activate the basolateral and centromedial parts of the amygdala. Our results demonstrate that rats detect the emotional arousal of recently aversively stimulated caregivers and suggest that cross-species social transmission of threat information may involve similar neural circuits in the amygdala as the within-species transmission.

Assessing and Modelling of Post-Traumatic Stress Disorder Using Molecular and Functional Biomarkers

Post-traumatic stress disorder (PTSD) is a complex psychological disorder that develops following exposure to traumatic events. PTSD is influenced by catalytic factors such as dysregulated hypothalamic-pituitary-adrenal (HPA) axis, neurotransmitter imbalances, and oxidative stress. Genetic variations may act as important catalysts, impacting neurochemical signaling, synaptic plasticity, and stress response systems. Understanding the intricate gene networks and their interactions is vital for comprehending the underlying mechanisms of PTSD. Focusing on the catalytic factors of PTSD is essential because they provide valuable insights into the underlying mechanisms of the disorder. By understanding these factors and their interplay, researchers may uncover potential targets for interventions and therapies, leading to more effective and personalized treatments for individuals with PTSD. The aforementioned gene networks, composed of specific genes associated with the disorder, provide a comprehensive view of the molecular pathways and regulatory mechanisms involved in PTSD. Through this study valuable insights into the disorder's underlying mechanisms and opening avenues for effective treatments, personalized interventions, and the development of biomarkers for early detection and monitoring are provided.

A prolonged stress rat model recapitulates some PTSD-like changes in sleep and neuronal connectivity

Chronic post-traumatic stress disorder (PTSD) exhibits psychological abnormalities during fear memory processing in rodent models. To simulate long-term impaired fear extinction in PTSD patients, we constructed a seven-day model with multiple prolonged stress (MPS) by modifying manipulation repetitions, intensity, and unpredictability of stressors. Behavioral and neural changes following MPS conveyed longitudinal PTSD-like effects in rats for 6 weeks. Extended fear memory was estimated through fear retrieval induced-freezing behavior and increased long-term serum corticosterone concentrations after MPS manipulation. Additionally, memory retrieval and behavioral anxiety tasks continued enhancing theta oscillation activity in the prefrontal cortex-basal lateral amygdala-ventral hippocampus pathway for an extended period. Moreover, MPS and remote fear retrieval stimuli disrupted sleep-wake activities to consolidate fear memory. Our prolonged fear memory, neuronal connectivity, anxiety, and sleep alteration results demonstrated integrated chronic PTSD symptoms in an MPS-induced rodent model.

A short pre-conception bout of predation risk affects both children and grandchildren

Traumatic events that affect physiology and behavior in the current generation may also impact future generations. We demonstrate that an ecologically realistic degree of predation risk prior to conception causes lasting changes in the first filial (F1) and second filial (F2) generations. We exposed male and female mice to a live rat (predator stress) or control (non-predator) condition for 5 min. Ten days later, stressed males and females were bred together as were control males and females. Adult F1 offspring from preconception-stressed parents responded to a mild stressor with more anxiety-like behavior and hyperarousal than offspring from control parents. Exposing these F1 offspring to the mild stressor increased neuronal activity (cFOS) in the hippocampus and altered glucocorticoid system function peripherally (plasma corticosterone levels). Even without the mild stressor, F1 offspring from preconception-stressed parents still exhibited more anxiety-like behaviors than controls. Cross-fostering studies confirmed that preconception stress, not maternal social environment, determined offspring behavioral phenotype. The effects of preconception parental stress were also unexpectedly persistent and produced similar behavioral phenotypes in the F2 offspring. Our data illustrate that a surprisingly small amount of preconception predator stress alters the brain, physiology, and behavior of future generations. A better understanding of the 'long shadow' cast by fearful events is critical for understanding the adaptive costs and benefits of transgenerational plasticity. It also suggests the intriguing possibility that similar risk-induced changes are the rule rather than the exception in free-living organisms, and that such multigenerational impacts are as ubiquitous as they are cryptic.

Restraint or immobilization: a comparison of methodologies for restricting free movement in rodents and their potential impact on physiology and behavior

Restriction of free movement has historically been used as a model for inducing acute and chronic stress in laboratory animals. This paradigm is one of the most widely employed experimental procedures for basic research studies of stress-related disorders. It is easy to implement, and it rarely involves any physical harm to the animal. Many different restraint methods have been developed with variations in the apparatuses used and the degree of limitation of movement. Unfortunately, very few studies directly compare the differential impact of the distinct protocols. Additionally, restraint and immobilization terms are not differentiated and are sometimes used interchangeably in the literature. This review offers evidence of great physiological differences in the impact of distinct restraint procedures in rats and mice and emphasizes the need for a standardized language on this topic. Moreover, it illustrates the necessity of additional systematic studies that compare the effects of the distinct restraint methodologies, which would help to decide better which procedure should be used depending on the objectives of each particular study.

On making (and turning adaptive to) maladaptive aversive memories in laboratory rodents

Fear conditioning and avoidance tasks usually elicit adaptive aversive memories. Traumatic memories are more intense, generalized, inflexible, and resistant to attenuation via extinction- and reconsolidation-based strategies. Inducing and assessing these dysfunctional, maladaptive features in the laboratory are crucial to interrogating posttraumatic stress disorder's neurobiology and exploring innovative treatments. Here we analyze over 350 studies addressing this question in adult rats and mice. There is a growing interest in modeling several qualitative and quantitative memory changes by exposing already stressed animals to freezing- and avoidance-related tests or using a relatively high aversive training magnitude. Other options combine aversive/fearful tasks with post-acquisition or post-retrieval administration of one or more drugs provoking neurochemical or epigenetic alterations reported in the trauma aftermath. It is potentially instructive to integrate these procedures and incorporate the measurement of autonomic and endocrine parameters. Factors to consider when defining the organismic and procedural variables, partially neglected aspects (sex-dependent differences and recent vs. remote data comparison) and suggestions for future research (identifying reliable individual risk and treatment-response predictors) are discussed.

Glucocorticoid-based pharmacotherapies preventing PTSD

Posttraumatic stress disorder (PTSD) is a highly disabling psychiatric condition that may arise after exposure to acute and severe trauma. It is a highly prevalent mental disorder worldwide, and the current treatment options for these patients remain limited due to low effectiveness. The time window right after traumatic events provides clinicians with a unique opportunity for preventive interventions against potential deleterious alterations in brain function that lead to PTSD. Some studies pointed out that PTSD patients present an abnormal function of the hypothalamic-pituitary-adrenal axis that may contribute to a vulnerability toward PTSD. Moreover, glucocorticoids have arisen as a promising option for preventing the disorder's development when administered in the aftermath of trauma. The present work compiles the recent findings of glucocorticoid administration for the prevention of a PTSD phenotype, from human studies to animal models of PTSD. Overall, glucocorticoid-based therapies for preventing PTSD demonstrated moderate evidence in terms of efficacy in both clinical and preclinical studies. Although clinical studies point out that glucocorticoids may not be effective for all patients' subpopulations, those with adequate traits might greatly benefit from them. Preclinical studies provide precise insight into the mechanisms mediating this preventive effect, showing glucocorticoid-based prevention to reduce long-lasting behavioral and neurobiological abnormalities caused by traumatic stress. However, further research is needed to delineate the precise mechanisms and the extent to which these interventions can translate into lower PTSD rates and morbidity. This article is part of the Special Issue on 'Fear, Anxiety and PTSD'.

Beyond monoamines: II. Novel applications for PET imaging in psychiatric disorders

Early applications of positron emission tomography (PET) in psychiatry sought to identify derangements of cerebral blood flow and metabolism. The need for more specific neurochemical imaging probes was soon evident, and these probes initially targeted the sites of action of neuroleptic (dopamine D₂ receptors) and psychoactive (serotonin receptors) drugs. For nearly 30 years, the centrality of monoamine dysfunction in psychiatric disorders drove the development of an armamentarium of monoaminergic PET radiopharmaceuticals and imaging methodologies. However, continued investments in monoamine-enhancing drug development realized only modest gains in efficacy and tolerability. As patent protection for many widely prescribed and profitable psychiatric drugs lapsed, drug development pipelines shifted away from monoamines in search of novel targets with the promises of improved efficacy, or abandoned altogether. Over this period, PET radiopharmaceutical development activities closely parallelled drug development priorities, resulting in the development of new PET imaging agents for non-monoamine targets. In part two of this review, we survey clinical research studies using the novel targets and radiotracers described in part one across major psychiatric application areas such as substance use disorders, anxiety disorders, eating disorders, personality disorders, mood disorders, and schizophrenia. Important limitations of the studies described are discussed, as well as key methodologic issues, challenges to the field, and the status of clinical trials seeking to exploit these targets for novel therapeutics.

Beyond monoamines: I. Novel targets and radiotracers for Positron emission tomography imaging in psychiatric disorders

With the emergence of positron emission tomography (PET) in the late 1970s, psychiatry had access to a tool capable of non-invasive assessment of human brain function. Early applications in psychiatry focused on identifying characteristic brain blood flow and metabolic derangements using radiotracers such as [¹⁵ O]H₂ O and [¹⁸ F]FDG. Despite the success of these techniques, it became apparent that more specific probes were needed to understand the neurochemical bases of psychiatric disorders. The first neurochemical PET imaging probes targeted sites of action of neuroleptic (dopamine D₂ receptors) and psychoactive (serotonin receptors) drugs. Based on the centrality of monoamine dysfunction in psychiatric disorders and the measured success of monoamine-enhancing drugs in treating them, the next 30 years witnessed the development of an armamentarium of PET radiopharmaceuticals and imaging methodologies for studying monoamines. Continued development of monoamine-enhancing drugs over this time however was less successful, realizing only modest gains in efficacy and tolerability. As patent protection for many widely prescribed and profitable psychiatric drugs lapsed, drug development pipelines shifted away from monoamines in search of novel targets with the promises of improved efficacy, or abandoned altogether. Over this period, PET radiopharmaceutical development activities closely paralleled drug development priorities resulting in the development of new PET imaging agents for non-monoamine targets. Part one of this review will briefly survey novel PET imaging targets with relevance to the field of psychiatry, which include the metabotropic glutamate receptor type 5 (mGluR5), purinergic P₂ X₇ receptor, type 1 cannabinoid receptor (CB₁ ), phosphodiesterase 10A (PDE10A), and describe radiotracers developed for these and other targets that have matured to human subject investigations. Current limitations of the targets and techniques will also be discussed.

Adverse maternal environment alters Oprl1 variant expression in mouse hippocampus

An adverse maternal environment (AME) and Western diet (WD) in early life predispose offspring toward cognitive impairment in humans and mice. Cognitive impairment associates with hippocampal dysfunction. An important regulator of hippocampal function is the hippocampal Nociceptin/Orphanin FQ (N/OFQ) system. Previous studies find links between dysregulation of hippocampal N/OFQ receptor (NOP) expression and impaired cognitive function. NOP is encoded by the opioid receptor-like 1 (Oprl1) gene that contains multiple mRNA variants and isoforms. Regulation of Oprl1 expression includes histone modifications within the promoter. We tested the hypothesis that an AME and a postweaning WD increase the expression of hippocampal Oprl1 and select variants concurrent with altered histone code in the promoter. We created an AME-WD model combining maternal WD and prenatal environmental stress plus postweaning WD in the mouse. We analyzed the hippocampal expression of Oprl1, Oprl1 variants, and histone modifications in the Oprl1 promoter in offspring at postnatal day (P) 21 and P100. An AME and an AME-WD significantly increased the total hippocampal expression of Oprl1 and variant V4 concurrently with an increased accumulation of active histone marks in the promoter of male offspring. We concluded that an AME and an AME-WD alter hippocampal Oprl1 expression in offspring through an epigenetic mechanism in a variant-specific and sex-specific manner. Altered hippocampal Oprl1 expression may contribute to cognitive impairment seen in adult males in this model. Epigenetic regulation of Oprl1 is a potential mechanism by which an AME and a WD may contribute to neurocognitive impairment in male offspring.

Anatomical and molecular features of the amygdalohippocampal transition area and its role in social and emotional behavior processes

The amygdalohippocampal transition area (AHi) has emerged as a critical nucleus of sociosexual behaviors such as mating, parenting, and aggression. The AHi has been overlooked in rodent and human amygdala studies until recently. The AHi is hypothesized to play a role in metabolic and cognitive functions as well as social behaviors based on its connectivity and molecular composition. The AHi is small nucleus rich in neuropeptide and hormone receptors and is contiguous with the ventral subiculum of the hippocampus-hence its designation as a "transition area". Literature focused on the AHi can be difficult to interpret because of changing nomenclature and conflation with neighboring nuclei. Here we summarize what is currently known about AHi structure and development, connections throughout the brain, molecular composition, and functional significance. We aim to delineate current knowledge regarding the AHi, identify potential functions with supporting evidence, and ultimately make clear the importance of the AHi in sociosexual function.

PACAP-PAC1R modulates fear extinction via the ventromedial hypothalamus

Exposure to traumatic stress can lead to fear dysregulation, which has been associated with posttraumatic stress disorder (PTSD). Previous work showed that a polymorphism in the PACAP-PAC1R (pituitary adenylate cyclase-activating polypeptide) system is associated with PTSD risk in women, and PACAP (ADCYAP1)-PAC1R (ADCYAP1R1) are highly expressed in the hypothalamus. Here, we show that female mice subjected to acute stress immobilization (IMO) have fear extinction impairments related to Adcyap1 and Adcyap1r1 mRNA upregulation in the hypothalamus, PACAP-c-Fos downregulation in the Medial Amygdala (MeA), and PACAP-FosB/ΔFosB upregulation in the Ventromedial Hypothalamus dorsomedial part (VMHdm). DREADD-mediated inhibition of MeA neurons projecting to the VMHdm during IMO rescues both PACAP upregulation in VMHdm and the fear extinction impairment. We also found that women with the risk genotype of ADCYAP1R1 rs2267735 polymorphism have impaired fear extinction.

TrkA-cholinergic signaling modulates fear encoding and extinction learning in PTSD-like behavior

Recent studies have suggested that the use of cognitive enhancers as adjuncts to exposure-based therapy in individuals suffering from post-traumatic stress disorder (PTSD) may be beneficial. Brain cholinergic signaling through basal forebrain projections to the hippocampus is an established pathway mediating fear response and cognitive flexibility. Here we employed a genetic strategy to enhance cholinergic activity through increased signaling of the NGF receptor TrkA. This strategy leads to increased levels of the marker of cholinergic activation, acetylcholine synthesizing enzyme choline acetyltransferase, in forebrain cholinergic regions and their projection areas such as the hippocampus. Mice with increased cholinergic activity do not display any neurobehavioral abnormalities except a selective attenuation of fear response and lower fear expression in extinction trials. Reduction in fear response is rescued by the GABA antagonist picrotoxin in mutant mice, and, in wild-type mice, is mimicked by the GABA agonist midazolam suggesting that GABA can modulate cholinergic functions on fear circuitries. Importantly, mutant mice also show a reduction in fear processing under stress conditions in a single prolonged stress (SPS) model of PTSD-like behavior, and augmentation of cholinergic signaling by the drug donepezil in wild-type mice promotes extinction learning in a similar SPS model of PTSD-like behavior. Donepezil is already in clinical use for the treatment of dementia suggesting a new translational application of this drug for improving exposure-based psychotherapy in PTSD patients.

Therapeutic potential of nociceptin/orphanin FQ peptide (NOP) receptor modulators for treatment of traumatic brain injury, traumatic stress, and their co-morbidities

The nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor is a member of the opioid receptor superfamily with N/OFQ as its endogenous agonist. Wide expression of the NOP receptor and N/OFQ, both centrally and peripherally, and their ability to modulate several biological functions has led to development of NOP receptor modulators by pharmaceutical companies as therapeutics, based upon their efficacy in preclinical models of pain, anxiety, depression, Parkinson's disease, and substance abuse. Both posttraumatic stress disorder (PTSD) and traumatic brain injury (TBI) are debilitating conditions that significantly affect the quality of life of millions of people around the world. PTSD is often a consequence of TBI, and, especially for those deployed to, working and/or living in a war zone or are first responders, they are comorbid. PTSD and TBI share common symptoms, and negatively influence outcomes as comorbidities of the other. Unfortunately, a lack of effective therapies or therapeutic agents limits the long term quality of life for either TBI or PTSD patients. Ours, and other groups, demonstrated that PTSD and TBI preclinical models elicit changes in the N/OFQ-NOP receptor system, and that administration of NOP receptor ligands alleviated some of the neurobiological and behavioral changes induced by brain injury and/or traumatic stress exposure. Here we review the past and most recent progress on understanding the role of the N/OFQ-NOP receptor system in PTSD and TBI neurological and behavioral sequelae. There is still more to understand about this neuropeptide system in both PTSD and TBI, but current findings warrant further examination of the potential utility of NOP modulators as therapeutics for these disorders and their co-morbidities. We advocate the development of standards for common data elements (CDE) reporting for preclinical PTSD studies, similar to current preclinical TBI CDEs. That would provide for more standardized data collection and reporting to improve reproducibility, interpretation and data sharing across studies.

Long-term follow-up assessment of opioid use outcomes among individuals with comorbid mental disorders and opioid use disorder treated with buprenorphine or methadone in a randomized clinical trial

AIMS

To investigate whether reduction in opioid use differs when treated by either buprenorphine-naloxone (BUP) or methadone (MET) among adults with comorbid opioid use disorder (OUD) and mental disorders.

DESIGN, SETTING AND PARTICIPANTS

In a randomized controlled trial, adults with OUD were randomized to 24 weeks of either BUP or MET treatment and were followed up in 3-yearly assessments. The present secondary analyses were based on 597 participants who completed all assessments.

MEASUREMENTS

The outcome measure was the number of days of using opioids per month during the follow-up period. The Mini-International Neuropsychiatric Interview (MINI) was used to classify participants into three groups: life-time mood disorder (n = 302), life-time mental disorder other than mood disorder (n = 114) and no mental disorder (n = 181). Medication treatment (BUP, MET, no treatment) during the follow-up period was a time-varying predictor.

FINDINGS

Based on zero-inflated Poisson (ZIP) mixed regression analysis, it was found that relative to no treatment, opioid use during the follow-up was significantly reduced by BUP [odds ratio (OR) = 0.12, 95% confidence interval (CI) = 0.07-0.21 for any use; risk ratio (RR) = 0.77, 95% CI =0.66-0.89 for days of use] and by MET [OR = 0.33, 95% CI = 0.25-0.45 for any use; RR = 0.78, 95% CI = 0.72-0.84 for days of use]. Relative to MET, BUP was associated with a lower likelihood of any opioid use among participants with mood disorders (OR = 0.52, 95% CI = 0.36-0.74) and for participants without mental disorder (OR = 0.37, 95% CI = 0.21-0.66) and fewer number of days using opioids (RR = 0.37, 95% CI = 0.25-0.56) among participants with other mental disorders.

CONCLUSIONS

Among adults with comorbid opioid use disorder and mental disorders, treatment with buprenorphine-naloxone produced greater reductions in opioid use than treatment with methadone.

Prevalence and risk factors for acute stress disorder in female victims of sexual assault

Sexual assault is one of the most traumatic events a person can experience. Despite this, information regarding the risk factors associated with the development of Acute Stress Disorder (ASD) in sexual assault victims is scarce. A follow-up prospective cohort study was designed to examine the prevalence and risk factors of ASD in women exposed to a recent sexual assault. A total of 156 women were treated at the Emergency Department of a university general hospital shortly after sexual assault. Sociodemographic, clinical and sexual assault-related variables were collected. The Acute Stress Disorder Interview was used to estimate the prevalence of ASD at three weeks post-SA. From the 156 victims, 66.6% (N = 104) met ASD diagnosis using DSM-5 criteria, whereas 59.6% (N = 93) met ASD diagnosis using DSM-IV criteria. The risk factors associated with the development of ASD were nationality, psychiatric history, peritraumatic dissociation and type of assault. In conclusion, the prevalence of ASD in female victims of recent sexual assault was high, affecting approximately two thirds of them. The recognition of the risk factors associated with ASD development, like peritraumatic dissociation or type of assault, may aid in the prompt detection of vulnerable women that require early and specific interventions shortly after trauma.

Role of Nociceptin/Orphanin FQ-NOP Receptor System in the Regulation of Stress-Related Disorders

Nociceptin/orphanin FQ (N/OFQ) is a 17-residue neuropeptide that binds the nociceptin opioid-like receptor (NOP). N/OFQ exhibits nucleotidic and aminoacidics sequence homology with the precursors of other opioid neuropeptides but it does not activate either MOP, KOP or DOP receptors. Furthermore, opioid neuropeptides do not activate the NOP receptor. Generally, activation of N/OFQ system exerts anti-opioids effects, for instance toward opioid-induced reward and analgesia. The NOP receptor is widely expressed throughout the brain, whereas N/OFQ localization is confined to brain nuclei that are involved in stress response such as amygdala, BNST and hypothalamus. Decades of studies have delineated the biological role of this system demonstrating its involvement in significant physiological processes such as pain, learning and memory, anxiety, depression, feeding, drug and alcohol dependence. This review discusses the role of this peptidergic system in the modulation of stress and stress-associated psychiatric disorders in particular drug addiction, mood, anxiety and food-related associated-disorders. Emerging preclinical evidence suggests that both NOP agonists and antagonists may represent a effective therapeutic approaches for substances use disorder. Moreover, the current literature suggests that NOP antagonists can be useful to treat depression and feeding-related diseases, such as obesity and binge eating behavior, whereas the activation of NOP receptor by agonists could be a promising tool for anxiety.

NOP receptor antagonism attenuates reinstatement of alcohol-seeking through modulation of the mesolimbic circuitry in male and female alcohol-preferring rats

In patients suffering from alcohol use disorder (AUD), stress and environmental stimuli associated with alcohol availability are important triggers of relapse. Activation of the nociceptin opioid peptide (NOP) receptor by its endogenous ligand Nociceptin/Orphanin FQ (N/OFQ) attenuates alcohol drinking and relapse in rodents, suggesting that NOP agonists may be efficacious in treating AUD. Intriguingly, recent data demonstrated that also blockade of NOP receptor reduced alcohol drinking in rodents. To explore further the potential of NOP antagonism, we investigated its effects on the reinstatement of alcohol-seeking elicited by administration of the α2 antagonist yohimbine (1.25 mg/kg, i.p.) or by environmental conditioning factors in male and female genetically selected alcohol-preferring Marchigian Sardinian (msP) rats. The selective NOP receptor antagonist LY2817412 (0.0, 3.0, 10.0, and 30.0 mg/kg) was first tested following oral (p.o.) administration. We then investigated the effects of LY2817412 (1.0, 3.0, 6.0 μg/μl/rat) microinjected into three candidate mesolimbic brain regions: the ventral tegmental area (VTA), the central nucleus of the amygdala (CeA), and the nucleus accumbens (NAc). We found that relapse to alcohol seeking was generally stronger in female than in male rats and oral administration of LY2817412 reduced yohimbine- and cue-induced reinstatement in both sexes. Following site-specific microinjections, LY2817412 reduced yohimbine-induced reinstatement of alcohol-seeking when administered into the VTA and the CeA, but not in the NAc. Cue-induced reinstatement was suppressed only when LY2817412 was microinjected into the VTA. Infusions of LY2817412 into the VTA and the CeA did not alter saccharin self-administration. These results demonstrate that NOP receptor blockade prevents the reinstatement of alcohol-seeking through modulation of mesolimbic system circuitry, providing further evidence of the therapeutic potential of NOP receptor antagonism in AUD.

Molecular impacts of childhood abuse on the human brain

Childhood abuse (CA) is a prevalent global health concern, increasing the risk of negative mental health outcomes later in life. In the literature, CA is commonly defined as physical, sexual, and emotional abuse, as well as neglect. Several mental disorders have been associated with CA, including depression, bipolar disorder, schizophrenia, and post-traumatic stress disorder, along with an increased risk of suicide. It is thought that traumatic life events occurring during childhood and adolescence may have a significant impact on essential brain functions, which may persist throughout adulthood. The interaction between the brain and the external environment can be mediated by epigenetic alterations in gene expression, and there is a growing body of evidence to show that such changes occur as a function of CA. Disruptions in the HPA axis, myelination, plasticity, and signaling have been identified in individuals with a history of CA. Understanding the molecular impact of CA on the brain is essential for the development of treatment and prevention measures. In this review, we will summarize studies that highlight the molecular changes associated with CA in the human brain, along with supporting evidence from peripheral studies and animal models. We will also discuss some of the limitations surrounding the study of CA and propose extracellular vesicles as a promising future approach in the field.

Neural connectome prospectively encodes the risk of post-traumatic stress disorder (PTSD) symptom during the COVID-19 pandemic

Background

The novel coronavirus (COVID-19) pandemic has affected humans worldwide and led to unprecedented stress and mortality. Detrimental effects of the pandemic on mental health, including risk of post-traumatic stress disorder (PTSD), have become an increasing concern. The identification of prospective neurobiological vulnerability markers for developing PTSD symptom during the pandemic is thus of high importance.

Methods

Before the COVID-19 outbreak (September 20, 2019-January 11, 2020), some healthy participants underwent resting-state functional connectivity MRI (rs-fcMRI) acquisition. We assessed the PTSD symptomology of these individuals during the peak of COVID-19 pandemic (February 21, 2020-February 28, 2020) in China. This pseudo-prospective cohort design allowed us to test whether the pre-pandemic neural connectome status could predict the risk of developing PTSD symptom during the pandemic.

Results

A total of 5.60% of participants (n = 42) were identified as being high-risk to develop PTSD symptom and 12.00% (n = 90) exhibited critical levels of PTSD symptoms during the COVID-19 pandemic. Pre-pandemic measures of functional connectivity (the neural connectome) prospectively classified those with heightened risk to develop PTSD symptom from matched controls (Accuracy = 76.19%, Sensitivity = 80.95%, Specificity = 71.43%). The trained classifier generalized to an independent sample. Continuous prediction models revealed that the same connectome could accurately predict the severity of PTSD symptoms within individuals (r ² = 0.31p<.0).

Conclusions

This study confirms COVID-19 break as a crucial stressor to bring risks developing PTSD symptom and demonstrates that brain functional markers can prospectively identify individuals at risk to develop PTSD symptom.

PTSD: Past, present and future implications for China

There has been a long history since human beings began to realize the existence of post-traumatic symptoms. Posttraumatic stress disorder (PTSD), a diagnostic category adopted in 1980 in the Diagnostic and Statistical Manual of Mental Disorders-Ⅲ, described typical clusters of psychiatric symptoms occurring after traumatic events. Abundant researches have helped deepen the understanding of PTSD in terms of epidemiological features, biological mechanisms, and treatment options. The prevalence of PTSD in general population ranged from 6.4% to 7.8% and was significantly higher among groups who underwent major public traumatic events. There has been a long way in the studies of animal models and genetic characteristics of PTSD. However, the high comorbidity with other stress-related psychiatric disorders and complexity in the pathogenesis of PTSD hindered the effort to find specific biological targets for PTSD. Neuroimage was widely used to elucidate the underlying neurophysiological mechanisms of PTSD. Functional MRI studies have showed that PTSD was linked to medial prefrontal cortex, anterior cingulate cortex and sub-cortical structures like amygdala and hippocampus, and to explore the functional connectivity among these brain areas which might reveal the possible neurobiological mechanism related to PTSD symptoms. For now, cognitive behavior therapy-based psychotherapy, including combination with adjunctive medication, showed evident treatment effects on PTSD. The emergence of more effective PTSD pharmacotherapies awaits novel biomarkers from further fundamental research. Several natural disasters and emergencies have inevitably increased the possibility of suffering from PTSD in the last two decades, making it critical to strengthen PTSD research in China. To boost PTSD study in China, the following suggestions might be helpful: (1) establishing a national psychological trauma recover project, and (2) exploring the mechanisms of PTSD with joint effort and strengthening the indigenized treatment of PTSD.

Nociceptin/orphanin FQ receptor system blockade as an innovative strategy for increasing resilience to stress

The ability to successfully cope with stress is known as 'resilience', and resilient individuals are less prone to develop psychopathologies. Understanding the neurobiological mechanisms of resilience may be instrumental to improve current therapies and benefit high-risk subjects. This review summarizes the complex interplay that exists between physiological and pathological responses to stressful events and the nociceptin/orphanin FQ (N/OFQ) - N/OFQ receptor (NOP) system, including: the effects of stress in regulating N/OFQ release and NOP expression; the ability of the N/OFQ-NOP system to modulate the hypothalamic-pituitary-adrenal axis; behavioral studies; and evidence in humans correlating this peptidergic system with psychopathologies. Available findings support the view that N/OFQ signaling stimulates the hypothalamic-pituitary-adrenal axis, thus increasing stress circulating hormones and corticotropin-releasing factor signaling. Additionally, activation of the NOP receptor inhibits monoamine transmission, including 5-HT, and this may contribute to maladaptive outcomes of stress. Ultimately, the N/OFQ system seems to have an important role in stress vulnerability, and blockade of NOP signaling may provide an innovative strategy for the treatment of stress related psychopathologies.

Genetics of human startle reactivity: A systematic review to acquire targets for an anxiety endophenotype

OBJECTIVES

Startle response is an objective physiological measure integral to the human defense system and a promising target for endophenotype investigations of anxiety. Given the alterations in startle reactivity observed among anxiety and related disorders, we searched for genetic variants associated with startle reactivity as they may be further involved in pathological anxiety risk.

METHODS

A systematic literature review was performed to identify genetic variants associated with startle reactivity in humans, specifically baseline and fear- or anxiety-potentiated startle.

RESULTS

The polymorphisms Val66Met (rs6265) from brain-derived neurotrophic factor (BDNF), Val158Met (rs4680) from catechol-O-methyltransferase (COMT), and the serotonin transporter-linked polymorphic region (5-HTTLPR) from the serotonin transporter gene (SLC6A4) were most commonly studied in human startle. In addition, several other genetic variants have also been identified as potential candidates that warrant further research, especially given their novelty in in the context of anxiety.

CONCLUSIONS

Similar to psychiatric genetic studies, the studies on startle reactivity primarily focus on candidate genes and are plagued by non-replication. Startle reactivity is a promising endophenotype that requires concerted efforts to collect uniformly assessed, large, well-powered samples and hypothesis-free genome-wide strategies. To further support startle as an endophenotype for anxiety, this review suggests advanced genetic strategies for startle research.

The advent of fear conditioning as an animal model of post-traumatic stress disorder: Learning from the past to shape the future of PTSD research

Translational research on post-traumatic stress disorder (PTSD) has produced limited improvements in clinical practice. Fear conditioning (FC) is one of the dominant animal models of PTSD. In fact, FC is used in many different ways to model PTSD. The variety of FC-based models is ill defined, creating confusion and conceptual vagueness, which in turn impedes translation into the clinic. This article takes a historical and conceptual approach to provide a comprehensive picture of current research and help reorient the research focus. This work historically reviews the variety of models that have emerged from the initial association of PTSD with FC, highlighting conceptual pitfalls that have limited the translation of animal research into clinical advances. We then provide some guidance on how future translational research could benefit from conceptual and technological improvements to translate basic findings in patients. This objective will require transdisciplinary approaches and should involve physicians, engineers, philosophers, and neuroscientists.

The NOP Receptor System in Neurological and Psychiatric Disorders: Discrepancies, Peculiarities and Clinical Progress in Developing Targeted Therapies

The nociceptin opioid peptide (NOP) receptor and its endogenous ligand nociceptin/orphanin FQ (N/OFQ) are the fourth members of the opioid receptor and opioid peptide families. Although they have considerable sequence homology to the other family members, they are not considered opioid per se because they do not have pharmacological profiles similar to the other family members. The number of NOP receptors in the brain is higher than the other family members, and NOP receptors can be found throughout the brain. Because of the widespread distribution of NOP receptors, N/OFQ and other peptide and small molecule agonists and antagonists have extensive CNS activities. Originally thought to be anti-opioid, NOP receptor agonists block some opioid activities, potentiate others, and modulate other activities not affected by traditional opiates. Because the effect of receptor activation can be dependent upon site of administration, state of the animal, and other variables, the study of NOP receptors has been fraught with contradictions and inconsistencies. In this article, the actions and controversies pertaining to NOP receptor activation and inhibition are discussed with respect to CNS disorders including pain (acute, chronic, and migraine), drug abuse, anxiety and depression. In addition, progress towards clinical use of NOP receptor-directed compounds is discussed.

Direct and Indirect Measurements of Sex Hormones in Rodents During Fear Conditioning

Fear conditioning (FC) is a widely accepted tool for the assessment of learning and memory processes in rodents related to normal and dysregulated acquired fear. The study of sex differences in fear learning and memory is vast and currently increasing. Sex hormones have proven to be crucial for fear memory formation in males and females, and several methods have been developed to assess this hormonal state in rats and mice. Herein, we explain a routine FC and extinction protocol, together with the evaluation of sex hormonal state in male and female rodents. We explain three protocols for the evaluation of this hormonal state directly from blood samples extracted during the procedure or indirectly through histological verification of the estrous cycle for females or behavioral assessment of social hierarchies in males. Although females have typically been considered to present great variability in sex hormones, it is highlighted that sex hormone assessment in males is as variable as in females and equally important for fear memory formation. The readout of these protocols has had a great impact on different fields of fear learning and memory study and appears essential when studying FC. The proven interaction with drugs involved in the modulation of these processes makes sex hormone assessment during FC a valuable tool for the development of effective treatments for fear-related disorders in men and women. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Fear conditioning and fear extinction Basic Protocol 2: Blood collection for direct measurement of sex hormone levels in fear conditioning Basic Protocol 3: Indirect measurement of sex hormones in females during fear conditioning Basic Protocol 4: Assessment of dominance status in males before a fear conditioning protocol Support Protocol: Construction of a confrontation tube.

Fear expression is reduced after acute and repeated nociceptin/orphanin FQ (NOP) receptor antagonism in rats: therapeutic implications for traumatic stress exposure

RATIONALE

Evaluation of pharmacotherapies for acute stress disorder (ASD) or post-traumatic stress disorder (PTSD) is challenging due to robust heterogeneity of trauma histories and limited efficacy of any single candidate to reduce all stress-induced effects. Pursuing novel mechanisms, such as the nociceptin/orphanin FQ (NOP) system, may be a viable path for therapeutic development and of interest as it is involved in regulation of relevant behaviors and recently implicated in PTSD and ASD.

OBJECTIVES

First, we evaluated NOP receptor antagonism on general behavioral performance and again following a three-species predator exposure model (Experiment 1). Then, we evaluated effects of NOP antagonism on fear memory expression (Experiment 2).

METHODS

Adult, male rats underwent daily administration of NOP antagonists (J-113397 or SB-612,111; 0-20 mg/kg, i.p.) and testing in acoustic startle, elevated plus maze, tail-flick, and open field tests. Effects of acute NOP antagonism on behavioral performance following predator exposure were then assessed. Separately, rats underwent fear conditioning and were later administered SB-612,111 (0-3 mg/kg, i.p.) prior to fear memory expression tests.

RESULTS

J-113397 and SB-612,111 did not significantly alter most general behavioral performance measures alone, suggesting minimal off-target behavioral effects of NOP antagonism. J-113397 and SB-612,111 restored performance in measures of exploratory behavior (basic movements on the elevated plus maze and total distance in the open field) following predator exposure. Additionally, SB-612,111 significantly reduced freezing behavior relative to control groups across repeated fear memory expression tests, suggesting NOP antagonism may be useful in dampening fear responses. Other measures of general behavioral performance were not significantly altered following predator exposure.

CONCLUSIONS

NOP antagonists may be useful as pharmacotherapeutics for dampening fear responses to trauma reminders, and the present results provide supporting evidence for the implication of the NOP system in the neuropathophysiology of dysregulations in fear learning and memory processes observed in trauma- and stress-related disorders.

Genetic and Neuroimaging Approaches to Understanding Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a highly disabling condition, increasingly recognized as both a disorder of mental health and social burden, but also as an anxiety disorder characterized by fear, stress, and negative alterations in mood. PTSD is associated with structural, metabolic, and molecular changes in several brain regions and the neural circuitry. Brain areas implicated in the traumatic stress response include the amygdala, hippocampus, and prefrontal cortex, which play an essential role in memory function. Abnormalities in these brain areas are hypothesized to underlie symptoms of PTSD and other stress-related psychiatric disorders. Conventional methods of studying PTSD have proven to be insufficient for diagnosis, measurement of treatment efficacy, and monitoring disease progression, and currently, there is no diagnostic biomarker available for PTSD. A deep understanding of cutting-edge neuroimaging genetic approaches is necessary for the development of novel therapeutics and biomarkers to better diagnose and treat the disorder. A current goal is to understand the gene pathways that are associated with PTSD, and how those genes act on the fear/stress circuitry to mediate risk vs. resilience for PTSD. This review article explains the rationale and practical utility of neuroimaging genetics in PTSD and how the resulting information can aid the diagnosis and clinical management of patients with PTSD.

D-Serine as the gatekeeper of NMDA receptor activity: implications for the pharmacologic management of anxiety disorders

Fear, anxiety, and trauma-related disorders, including post-traumatic stress disorder (PTSD), are quite common and debilitating, with an estimated lifetime prevalence of ~28% in Western populations. They are associated with excessive fear reactions, often including an inability to extinguish learned fear, increased avoidance behavior, as well as altered cognition and mood. There is an extensive literature demonstrating the importance of N-methyl-D-aspartate receptor (NMDAR) function in regulating these behaviors. NMDARs require the binding of a co-agonist, D-serine or glycine, at the glycine modulatory site (GMS) to function. D-serine is now garnering attention as the primary NMDAR co-agonist in limbic brain regions implicated in neuropsychiatric disorders. L-serine is synthesized by astrocytes, which is then transported to neurons for conversion to D-serine by serine racemase (SR), a model we term the 'serine shuttle.' The neuronally-released D-serine is what regulates NMDAR activity. Our review discusses how the systems that regulate the synaptic availability of D-serine, a critical gatekeeper of NMDAR-dependent activation, could be targeted to improve the pharmacologic management of anxiety-related disorders where the desired outcomes are the facilitation of fear extinction, as well as mood and cognitive enhancement.

The effect of polymorphisms in startle-related genes on anxiety symptom severity

Given the limited effectiveness of treatments for pathological anxiety, there is a pressing need to identify genetic markers that can aid the precise selection of treatments and optimize treatment response. Anxiety and startle response levels demonstrate a direct relationship, and previous literature suggests that exaggerated startle reactivity may serve as an endophenotype of pathological anxiety. In addition, genetic variants related to startle reactivity may play a role in the etiology of pathological anxiety. In the current study, we selected 22 single nucleotide polymorphisms (SNPs) related to startle reactivity in the literature, and examined their association with anxiety symptom severity across psychiatric disorders (n = 508), and in a subset of patients with an anxiety disorder (n = 298). Overall, none of the SNPs pass correction for multiple independent tests. However, across psychiatric patients, rs6323 from the monoamine oxidase A (MAOA) gene and rs324981 from the neuropeptide S receptor 1 (NPSR1) gene were nominally associated with baseline anxiety symptom severity (p = 0.017, 0.023). These preliminary findings provide support for investigating startle-related genetic variants to identify biomarkers of anxiety symptom severity.

Rodent models of post-traumatic stress disorder: behavioral assessment

Although the etiology and expression of psychiatric disorders are complex, mammals show biologically preserved behavioral and neurobiological responses to valent stimuli which underlie the use of rodent models of post-traumatic stress disorder (PTSD). PTSD is a complex phenotype that is difficult to model in rodents because it is diagnosed by patient interview and influenced by both environmental and genetic factors. However, given that PTSD results from traumatic experiences, rodent models can simulate stress induction and disorder development. By manipulating stress type, intensity, duration, and frequency, preclinical models reflect core PTSD phenotypes, measured through various behavioral assays. Paradigms precipitate the disorder by applying physical, social, and psychological stressors individually or in combination. This review discusses the methods used to trigger and evaluate PTSD-like phenotypes. It highlights studies employing each stress model and evaluates their translational efficacies against DSM-5, validity criteria, and criteria proposed by Yehuda and Antelman's commentary in 1993. This is intended to aid in paradigm selection by informing readers about rodent models, their benefits to the clinical community, challenges associated with the translational models, and opportunities for future work. To inform PTSD model validity and relevance to human psychopathology, we propose that models incorporate behavioral test batteries, individual differences, sex differences, strain and stock differences, early life stress effects, biomarkers, stringent success criteria for drug development, Research Domain Criteria, technological advances, and cross-species comparisons. We conclude that, despite the challenges, animal studies will be pivotal to advances in understanding PTSD and the neurobiology of stress.

Identification of significant gene biomarkers of low back pain caused by changes in the osmotic pressure of nucleus pulposus cells

The incidence of intervertebral disc (IVD) degeneration disease, caused by changes in the osmotic pressure of nucleus pulposus (NP) cells, increases with age. In general, low back pain is associated with IVD degeneration. However, the mechanism and molecular target of low back pain have not been elucidated, and there are no data suggesting specific biomarkers of low back pain. Therefore, the research aims to identify and verify the significant gene biomarkers of low back pain. The differentially expressed genes (DEGs) were screened in the Gene Expression Omnibus (GEO) database, and the identification and analysis of significant gene biomarkers were also performed with various bioinformatics programs. A total of 120 patients with low back pain were recruited. Before surgery, the degree of pain was measured by the numeric rating scale (NRS), which enables comparison of the pain scores from individuals. After surgery, IVD tissues were obtained, and NP cells were isolated. The NP cells were cultured in two various osmotic media, including iso-osmotic media (293 mOsm/kg H₂O) to account for the morbid environment of NP cells in IVD degeneration disease and hyper-osmotic media (450 mOsm/kg H₂O) to account for the normal condition of NP cells in healthy individuals. The relative mRNA expression levels of CCL5, OPRL1, CXCL13, and SST were measured by quantitative real-time PCR in the in vitro analysis of the osmotic pressure experiments. Finally, correlation analysis and a neural network module were employed to explore the linkage between significant gene biomarkers and pain. A total of 371 DEGs were identified, including 128 downregulated genes and 243 upregulated genes. Furthermore, the four genes (CCL5, OPRL1, SST, and CXCL13) were identified as significant gene biomarkers of low back pain (P < 0.001) based on univariate linear regression, and CCL5 (odds ratio, 34.667; P = 0.003) and OPRL1 (odds ratio, 19.875; P < 0.001) were significantly related to low back pain through multivariate logistic regression. The expression of CCL5 and OPRL1 might be correlated with low back pain in patients with IVD degeneration disease caused by changes in the osmotic pressure of NP cells.

Plasma microRNA Array Analysis Identifies Overexpressed miR-19b-3p as a Biomarker of Bipolar Depression Distinguishing From Unipolar Depression

OBJECTIVES

The clinical characteristics of bipolar disorder (current major depressive episode) (BD) overlap with unipolar depressive disorder (UD), which makes it difficult to perform an accurate diagnosis. We identified plasma microRNAs (miRNAs) that distinguished BD from UD and explored the relationship between miRNA expression levels and clinical characteristics.

METHODS

Total miRNAs from blood plasma from seven UD patients, seven BD patients, and six controls were analyzed. The identified miRNAs were validated in a separate population group. Depression severity and early life adversities were assessed. Bioinformatic analysis was conducted to investigate the target genes that were identified and the pathways associated with the altered miRNAs.

RESULTS

Compared to controls, 42 miRNAs were differentially expressed in patients. miR-19b-3p, miR-3921, and miR-1180-3p were selected to validate the microarray results. Only miR-19b-3p was validated as down-regulated in patients. The primary predicted genes associated with miR-19b-3p were MAPK1, PTEN, and PRKAA1. The most relevant KEGG pathways included mTOR, FoxO, and the PI3-K/Akt signaling pathway. BD patients were more likely to have higher expression levels of miR-19b-3p and more severe childhood trauma experience compared to UD patients.

CONCLUSIONS

Plasma miR-19b-3p is a potential non-invasive biomarker that might be useful in distinguishing UD from BD. miR-19b3p was predicted to be involved in the pathway of inflammatory dysregulation associated with experiencing early childhood trauma.

Depression genetic risk score is associated with anhedonia-related markers across units of analysis

Investigations of pathophysiological mechanisms implicated in vulnerability to depression have been negatively impacted by the significant heterogeneity characteristic of psychiatric syndromes. Such challenges are also reflected in numerous null findings emerging from genome-wide association studies (GWAS) of depression. Bolstered by increasing sample sizes, recent GWAS studies have identified genetics variants linked to MDD. Among them, Okbay and colleagues (Nat. Genet. 2016 Jun;48(6):624-33) identified genetic variants associated with three well-validated depression-related phenotypes: subjective well-being, depressive symptoms, and neuroticism. Despite this progress, little is known about psychopathological and neurobiological mechanisms underlying such risk. To fill this gap, a genetic risk score (GRS) was computed from the Okbay's study for a sample of 88 psychiatrically healthy females. Across two sessions, participants underwent two well-validated psychosocial stressors, and performed two separate tasks probing reward learning both before and after stress. Analyses tested whether GRS scores predicted anhedonia-related phenotypes across three units of analyses: self-report (Snaith Hamilton Pleasure Scale), behavior (stress-induced changes in reward learning), and circuits (stress-induced changes in striatal reward prediction error; striatal volume). GRS scores were negatively associated with anhedonia-related phenotypes across all units of analyses but only circuit-level variables were significant. In addition, the amount of explained variance was systematically larger as variables were putatively closer to the effects of genes (self-report < behavior < neural circuitry). Collectively, findings implicate anhedonia-related phenotypes and neurobiological mechanisms in increased depression vulnerability, and highlight the value of focusing on fundamental dimensions of functioning across different units of analyses.

Nociceptin impairs acquisition of novel object recognition memory in perirhinal cortex

Nociceptin/Orphanin FQ (N/OFQ) plays an important role in the regulation of spatial, fear and recognition memories. N/OFQ receptors are highly distributed in the perirhinal cortex, which is a key brain area involved in modulating novel object recognition (NOR) memory. However, the role of N/OFQ in NOR memory in the perirhinal cortex was still unknown. Moreover, the effects of N/OFQ on different stages of NOR memory were still unclear. In NOR task, we found that pre-training intracerebroventricular (icv) injection of N/OFQ (0.3 and 1 nmol) impaired long-term memory in a dose-dependent manner. However, icv infusion of N/OFQ immediately after training did not affect NOR memory consolidation even at a high dose of 3 nmol. Pre-test icv injection of N/OFQ (1 nmol) also did not influence NOR memory retrieval. These data indicate that N/OFQ negatively modulates long-term NOR memory during the acquisition phase. Furthermore, the amnesia effect of N/OFQ (1 nmol, icv) could be antagonist by pre-treatment with the selective N/OFQ receptor antagonist [Nphe1]N/OFQ(1-13)NH2 (10 nmol, icv), indicating pharmacological specificity. Then, we found that pre-training infusion of N/OFQ (0.1 and 0.3 nmol/side) into the bilateral perirhinal cortex impaired long-term NOR memory, suggesting the perirhinal cortex is a critical brain structure in mediating the amnesic effect of N/OFQ in NOR task. In conclusion, our data, for the first time, indicate that N/OFQ in the perirhinal cortex impairs NOR memory acquisition through the NOP receptors.

Decreased Nociceptin Receptors Are Related to Resilience and Recovery in College Women Who Have Experienced Sexual Violence: Therapeutic Implications for Posttraumatic Stress Disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is a stress disorder that develops in only some individuals following a traumatic event. Data suggest that a substantial fraction of women recover after sexual violence. Thus, the investigation of stress and antistress neuropeptides in this sample has the potential to inform the neurochemistry of resilience following trauma. Nociceptin is an antistress neuropeptide in the brain that promotes resilience in animal models of PTSD.

METHODS

[¹¹C]NOP-1A positron emission tomography was used to measure the in vivo binding to nociceptin receptors in 18 college women who had experienced sexual violence irrespective of whether they met DSM-5 diagnostic criteria for PTSD. [¹¹C]NOP-1A data from 18 healthy control subjects were also included to provide a contrast with the sexual violence group. [¹¹C]NOP-1A total distribution volume (V_T) in the regions of interest were measured with kinetic analysis using the arterial input function. The relationships between regional V_T and Clinician-Administered PTSD Scale for DSM-5 total symptom and subscale severity were examined using correlational analyses.

RESULTS

No differences in [¹¹C]NOP-1A V_T were noted between the sexual violence and control groups. V_T in the midbrain and cerebellum were positively correlated with PTSD total symptom severity in the past month before positron emission tomography. Intrusion/re-experiencing and avoidance subscale symptoms drove this relationship. Stratification of subjects by a DSM-5 PTSD diagnosis and contrasting their V_T with that in control subjects showed no group differences.

CONCLUSIONS

Decreased midbrain and cerebellum nociceptin receptors are associated with less severe PTSD symptoms. Medications that target nociceptin should be explored to prevent and treat PTSD.

Animal Models of PTSD: A Critical Review

The goals of animal research in post-traumatic stress disorder (PTSD) include better understanding the neurophysiological etiology of PTSD, identifying potential targets for novel pharmacotherapies, and screening drugs for their potential use as PTSD treatment in humans. Diagnosis of PTSD relies on a patient interview and, as evidenced by changes to the diagnostic criteria in the DSM-5, an adequate description of this disorder in humans is a moving target. Therefore, it may seem insurmountable to model the construct of PTSD in animals such as rodents. Fortunately, the neural circuitry involved in fear and anxiety, thought to be essential to the etiology of PTSD in humans, is highly conserved throughout evolution. Furthermore, many symptoms can be modeled using behavioral tests that have face, construct, and predictive validity. Because PTSD is precipitated by a definite traumatic experience, animal models can simulate the induction of PTSD, and test causal factors with longitudinal designs. Accordingly, several animal models of physical and psychological trauma have been established. This review discusses the widely used animal models of PTSD in rodents, and overviews their strengths and weaknesses in terms of face, construct, and predictive validity.

Targeting opioid dysregulation in depression for the development of novel therapeutics

Since the serendipitous discovery of the first class of modern antidepressants in the 1950's, all pharmacotherapies approved by the Food and Drug Administration for major depressive disorder (MDD) have shared a common mechanism of action, increased monoaminergic neurotransmission. Despite the widespread availability of antidepressants, as many as 50% of depressed patients are resistant to these conventional therapies. The significant length of time required to produce meaningful symptom relief with these medications, 4-6 weeks, indicates that other mechanisms are likely involved in the pathophysiology of depression which may yield more viable targets for drug development. For decades, no viable candidate target with a different mechanism of action to that of conventional therapies proved successful in clinical studies. Now several exciting avenues for drug development are under intense investigation. One of these emerging targets is modulation of endogenous opioid tone. This review will evaluate preclinical and clinical evidence pertaining to opioid dysregulation in depression, focusing on the role of the endogenous ligands endorphin, enkephalin, dynorphin, and nociceptin/orphanin FQ (N/OFQ) and their respective receptors, mu (MOR), delta (DOR), kappa (KOR), and the N/OFQ receptor (NOP) in mediating behaviors relevant to depression and anxiety. Finally, putative opioid based antidepressants that are under investigation in clinical trials, ALKS5461, JNJ-67953964 (formerly LY2456302 and CERC-501) and BTRX-246040 (formerly LY-2940094) will be discussed. This review will illustrate the potential therapeutic value of targeting opioid dysregulation in developing novel therapies for MDD.