Stress in Regulation of GABA Amygdala System and Relevance to Neuropsychiatric Diseases

Stress and substance use disorders: risk, relapse, and treatment outcomes

Stress has long been associated with substance misuse and substance use disorders (SUDs). The past two decades have seen a surge in research aimed at understanding the underlying mechanisms driving this association. This Review introduces a multilevel "adaptive stress response" framework, encompassing a stress baseline, acute reaction, and recovery with return-to-homeostasis phase that occurs at varying response times and across domains of analysis. It also discusses evidence showing the disruption of this adaptive stress response in the context of chronic and repeated stressors, trauma, adverse social and drug-related environments, as well as with acute and chronic drug misuse and with drug withdrawal and abstinence sequelae. Subjective, cognitive, peripheral, and neurobiological disruptions in the adaptive stress response phases and their link to inflexible, maladaptive coping; increased craving; relapse risk; and maintenance of drug intake are also presented. Finally, the prevention and treatment implications of targeting this "stress pathophysiology of addiction" are discussed, along with specific aspects that may be targeted in intervention development to rescue stress-related alterations in drug motivation and to improve SUD treatment outcomes.

Peripubertal antagonism of corticotropin-releasing factor receptor 1 results in sustained, sex-specific changes in behavioral plasticity and the transcriptomic profile of the amygdala

Peripuberty is a significant period of neurodevelopment with long-lasting effects on the brain and behavior. Blocking type 1 corticotropin-releasing factor receptors (CRFR1) in neonatal and peripubertal rats attenuates detrimental effects of early-life stress on neural plasticity, behavior, and stress hormone action, long after exposure to the drug has ended. CRFR1 antagonism can also impact neural and behavioral development in the absence of stressful stimuli, suggesting sustained alterations under baseline conditions. To investigate this further, we administered a CRFR1 antagonist (CRFR1a), R121919, to young adolescent male and female rats across 4 days. Following each treatment, rats were tested for locomotion, social behavior, mechanical allodynia, or PPI of the acoustic startle reflex. Acute CRFR1 blockade immediately reduced PPI in peripubertal males, but not females. In adulthood, each assay was repeated without CRFR1a exposure to test for long-term effects of the adolescent treatment, with males continuing to experience deficits in PPI, while females displayed altered locomotion, PPI, and social behavior. The amygdala was collected to measure long- term effects on gene expression in pathways related to neural plasticity and neurodevelopmental disorders. Relative expression of cannabinoid type 1 receptors (CB1R), which mediate sensorimotor and HPA function, was also measured. In the adult amygdala, peripubertal CRFR1a induced alterations in pathways related to neural plasticity and stress in males and lower expression of CB1R protein in females. Understanding how acute exposure to neuropharmacological agents can have sustained impacts on brain and behavior, in the absence of further exposures, has important clinical implications for adolescent psychiatric treatment protocols.

The Relationship between Canine Behavioral Disorders and Gut Microbiome and Future Therapeutic Perspectives

Canine behavioral disorders have become one of the most common concerns and challenging issues among dog owners. Thus, there is a great demand for knowledge about various factors affecting dogs' emotions and well-being. Among them, the gut-brain axis seems to be particularly interesting, especially since in many instances the standard treatment or behavioral therapies insufficiently improve animal behavior. Therefore, to face this challenge, the search for novel therapeutic methods is highly required. Existing data show that mammals' gut microbiome, immune system, and nervous system are in continuous communication and influence animal physiology and behavior. This review aimed to summarize and discuss the most important scientific evidence on the relationship between mental disorders and gut microbiota in dogs, simultaneously presenting comparable outcomes in humans and rodent models. A comprehensive overview of crucial mechanisms of the gut-brain axis is included. This refers especially to the neurotransmitters crucial for animal behavior, which are regulated by the gut microbiome, and to the main microbial metabolites-short-chain fatty acids (SCFAs). This review presents summarized data on gut dysbiosis in relation to the inflammation process within the organism, as well as the activation of the hypothalamic-pituitary-adrenal (HPA) axis. All of the above mechanisms are presented in this review in strict correlation with brain and/or behavioral changes in the animal. Additionally, according to human and laboratory animal studies, the gut microbiome appears to be altered in individuals with mental disorders; thus, various strategies to manipulate the gut microbiota are implemented. This refers also to the fecal microbiome transplantation (FMT) method, based on transferring the fecal matter from a donor into the gastrointestinal tract of a recipient in order to modulate the gut microbiota. In this review, the possible effects of the FMT procedure on animal behavioral disorders are discussed.

The impact of telecom industry employees' stress perception on job burnout: moderated mediation model

BACKGROUND

The rapid development of the telecommunications industry in the post-COVID-19 era has brought tremendous pressure to employees making them a high-risk group for job burnout. However, prior research paid less attention to the burnout of employees. Furthermore, social support and gender have separate effects on job burnout. This study explores the mechanism of stress perception on job burnout and examines the roles of social support and gender amid it.

METHOD

This cross-sectional study was conducted from June 2023 to August 2023 in mainland China. A total of 39,507 were recruited by random sampling and online questionnaires, and 28,204 valid questionnaires were retained. SPSS (version 26.0) and PROCESS (Model 4 & 7) were used for correlation analysis, mediation analysis, and mediated moderation analysis.

RESULT

Stress perception can positively predict the level of job burnout of employees in the telecommunications industry, and social support plays a partial mediating role, accounts for 8.01% of the total effect, gender moderates the first half of the path in this mediation model. At the same pressure level, female can perceive more social support than male.

CONCLUSIONS

Under high pressure background, employees' job burnout varies depending on gender and the perception of social support. Therefore, telecommunications industry managers should adopt decompression measures and targeted social support resources for different groups.

Neurobiology of bruxism: The impact of stress (Review)

Bruxism is a non-functional involuntary muscle activity that affects more than one-third of the population at some point in their lives. A number of factors have been found to be related to the etiopathogenesis of bruxism; therefore, the condition is considered multifactorial. The most commonly accepted factor is stress. Stress has long been considered to increase muscle tone and to reduce the pain threshold. Current evidence indicates that exposure to chronic stress, distress and allostatic load ignite neurological degeneration and the attenuation of critical neuronal pathways that are highly implicated in the orofacial involuntary muscle activity. The present review discusses the negative effects that chronic stress exerts on certain parts of the central nervous system and the mechanisms through which these changes are involved in the etiopathogenesis of bruxism. The extent of these morphological and functional changes on nerves and neuronal tracts provides valuable insight into the obstacles that need to be overcome in order to achieve successful treatment. Additionally, particular emphasis is given on the effects of bruxism on the central nervous system, particularly the activation of the hypothalamic-pituitary-adrenal axis, as this subsequently induces an increase in circulating corticosterone levels, also evidenced by increased levels of salivary cortisol, thereby transforming bruxism into a self-reinforcing loop.

Fermented mixed grain ameliorates chronic stress-induced depression-like behavior and memory deficit

Fermented mixed grain (FG) has beneficial anti-cancer, antioxidant, and anti-inflammatory effects. In this study, we investigated the effects of FG on gut inflammation, brain dysfunction, and anxiety/depression-like behavior induced by unpredictable chronic mild stress (UCMS) in mice. Mice were administered mixed grain or FG for 3 weeks and were then exposed to UCMS for 4 weeks. FG administration ameliorated stress-induced anxiety/despair-like behavior. FG administration also prevented UCMS-induced memory impairment. Additionally, the mRNA levels of 5-HTR1A and IL-6 were restored to normal levels in the brains of FG-administered mice. FG administration also inhibited intestinal damage in stressed mice compared with that in the UCMS (without FG) group. These results suggest that FG can alleviate stress-induced intestinal damage, brain dysfunction, and cognitive impairment.

Postweaning Social Isolation Alters Puberty Onset by Suppressing Electrical Activity of Arcuate Kisspeptin Neurons

INTRODUCTION

Postweaning social isolation (PWSI) in rodents is an advanced psychosocial stress model in early life. Some psychosocial stress, such as restrain and isolation, disrupts reproductive physiology in young and adult periods. Mechanisms of early-life stress effects on central regulation of reproduction need to be elucidated. We have investigated the effects of PWSI on function of arcuate kisspeptin (ARCKISS1) neurons by using electrophysiological techniques combining with monitoring of puberty onset and estrous cycle in male and female Kiss1-Cre mice.

METHODS

Female mice were monitored for puberty onset with vaginal opening examination during social isolation. After isolation, the estrous cycle of female mice was monitored with vaginal cytology. Anxiety-like behavior of mice was determined by an elevated plus maze test. Effects of PWSI on electrophysiology of ARCKISS1 neurons were investigated by the patch clamp method after intracranial injection of AAV-GFP virus into arcuate nucleus of Kiss1-Cre mice after the isolation period.

RESULTS

We found that both male and female isolated mice showed anxiety-like behavior. PWSI caused delay in vaginal opening and extension in estrous cycle length. Spontaneous-firing rates of ARCKISS1 neurons were significantly lower in the isolated male and female mice. The peak amplitude of inhibitory postsynaptic currents to ARCKISS1 neurons was higher in the isolated mice, while frequency of excitatory postsynaptic currents was higher in group-housed mice.

CONCLUSION

These findings demonstrate that PWSI alters pre- and postpubertal reproductive physiology through metabolic and electrophysiological pathways.

Gut-Brain Axis Impact on Canine Anxiety Disorders: New Challenges for Behavioral Veterinary Medicine

Anxiety disorders in dogs are ever-growing and represent an important concern in the veterinary behavior field. These disorders are often disregarded in veterinary clinical practice, negatively impacting the animal's and owner's quality of life. Moreover, these anxiety disorders can potentially result in the abandonment or euthanasia of dogs. Growing evidence shows that the gut microbiota is a central player in the gut-brain axis. A variety of microorganisms inhabit the intestines of dogs, which are essential in maintaining intestinal homeostasis. These microbes can impact mental health through several mechanisms, including metabolic, neural, endocrine, and immune-mediated pathways. The disruption of a balanced composition of resident commensal communities, or dysbiosis, is implicated in several pathological conditions, including mental disorders such as anxiety. Studies carried out in rodent models and humans demonstrate that the intestinal microbiota can influence mental health through these mechanisms, including anxiety disorders. Furthermore, novel therapeutic strategies using prebiotics and probiotics have been shown to ameliorate anxiety-related symptoms. However, regarding the canine veterinary behavior field, there is still a lack of insightful research on this topic. In this review, we explore the few but relevant studies performed on canine anxiety disorders. We agree that innovative bacterial therapeutical approaches for canine anxiety disorders will become a promising field of investigation and certainly pave the way for new approaches to these behavioral conditions.

Distinct mechanisms of allopregnanolone and diazepam underlie neuronal oscillations and differential antidepressant effect

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

Aggressive parenting: social, medical and legal aspects

OBJECTIVE

Aim: To examine the impacts of aggressive parenting on physical, mental and emotional development; outcomes for society; possible ways of prevention of children' rights or health violation and responsibility of parents to optimize well-being of children.

PATIENTS AND METHODS

Materials and Methods: The analysis of scientific data has been conducted on the basis of PubMed, Scopus and Web of Science databases in order to collect the existed results of researches about social and medical aspects of impact of aggressive parenting. The formal-legal method was used to interpret the provisions of legislation regarding the protection of personal non-property rights and responsibilities of parents and children.

CONCLUSION

Conclusions: Aggressive parenting affects children of all ages and is associated with chronic stress and long-term negative impacts on physical development, cognitive and behavioral dysfunction, socioemotional difficulties, social and psychological dysfunction in adulthood. Aggressive parenting triggers a child' aggressive behavior which is considered as a predictor of adult's criminality. From a legal standpoint, aggressive parenting is a form of violation of the responsibility of parents to educate a child, which is an element of family legal relations regulated by the norms of the family law institution known as ≪Personal non-property rights and responsibilities of parents and children". The definition of aggressive parenting has been defined with its legal features and characteristics. Effective prevention methods should be directed to predict possible further parental violence, intervention programs to reduce outcomes of aggressive parenting and to improve the ways of responsibility in procedural and material aspects of law.

Nuclear localization of alpha-synuclein induces anxiety-like behavior in mice by decreasing hippocampal neurogenesis and pathologically affecting amygdala circuits

Fear and anxiety are common in Parkinson's disease (PD) and may be caused by pathologies outside the dopaminergic system. Increasing evidence has shown that alpha-synuclein (α-syn) is involved in the development of anxiety in PD. In this study, we examined the effects of α-syn nuclear translocation on anxiety-like behavior in mice by overexpressing α-syn in the nuclei of the cell in the hippocampus. Our results show that α-syn overexpression in the nuclei increased the excitability of hippocampal neurons and activated NG2 glial cells and promoted the synthesis and release of γ-aminobutyric acid (GABA). And nuclear localization of α-syn led to the loss of neurotrophic factors and decreased neurogenesis. Meanwhile, the hippocampus and amygdala acted synergistically, resulting in pathologic accumulation of α-syn and gliosis in the amygdala and caused loss of interneurons. These events led to the impairments of hippocampus and amygdala function, which ultimately induced anxiety-like behavior in mice. The findings obtained in our present study indicate that excessive nuclear translocation of α-syn in hippocampal neurons and damage to the amygdala circuits may be important in the development of anxiety in PD.

The possible "calming effect" of subchronic supplementation of a standardised phospholipid carrier-based Melissa officinalis L. extract in healthy adults with emotional distress and poor sleep conditions: results from a prospective, randomised, double-blinded, placebo-controlled clinical trial

Background: Emotional distress conditions such as depression, anxiety, stress, and poor sleep are widespread health problems that have a significant impact on people's lives. Conventional drugs are commonly prescribed to treat emotional distress and poor sleep conditions; however, these medications have several limitations and have shown multiple side effects. Over recent years botanicals-based pharmacological agents have gained increasing research and clinical interest in the management of emotional distress and sleep disorder. Of note, Melissa officinalis L. (MO) leaf extract has demonstrated considerable neuropharmacological properties both in animal and human studies and has emerged as a promising natural "calming agent." However, research in this area is limited, and more studies are needed to validate its efficacy in amelioration of emotional distress and poor sleep conditions. Objectives: We aimed to assess the pharmacological effects of subchronic supplementation of an innovative standardised phospholipid carrier-based MO aqueous extract on emotional distress and poor sleep conditions. Design: A 3-week prospective, randomised, placebo-controlled, parallel-group, double-blinded clinical trial was conducted in 100 healthy adults complaining of a moderate degree of depression, anxiety, or stress, with scores of ≥14, ≥10, and ≥19, respectively, in the self-report Depression, Anxiety, and Stress Scale (DASS-42) or poor sleep, as indicated by the score of >5 in the Pittsburgh Sleep Quality Index (PSQI) scale. In addition, the impact of emotional distress and/or poor sleep on participants' mental wellbeing, emotional feelings, and quality of life was also assessed using the self-reported Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS), Positive and Negative Affect Schedule (PANAS) scale, and quality of life (WHO-QoL-BREF) scale, respectively. Results: Oral supplementation of 200 mg of phospholipid-based MO aqueous extract (Relissa™) tablets twice a day (i.e., 400 mg/day) for 3 weeks led to significant improvements in the depressive mood, anxiety, stress, positive and negative affect (emotional feelings), overall mental wellbeing, and quality-of-life scores (all p values <0.001). Supplementation of MO extract was well tolerated, and no treatment-emergent effects or serious adverse events were reported. Conclusion: According to the results of this study, the phospholipid carrier-based MO aqueous extract possesses considerable neuropharmacological properties, and its supplementation may provide a promising therapeutic option for the management of moderate emotional distress and/or poor sleep conditions. Clinical Trial Registration: clinicaltrials.gov, identifier NCT05602688.

Effect of dietary gamma aminobutyric acid (GABA) modulated the growth performance, immune and antioxidant capacity, digestive enzymes, intestinal histology and gene expression of Nile tilapia (Oreochromisniloticus)

Dietary GABA plays an important role in a variety of physiological functions in animals, but this has been rarely reported in fish. This study investigated the effects of dietary supplementation with GABA on growth, serum antioxidant indicators, digestive enzyme activities, intestinal morphology, and the gene expression of Nile tilapia. Diets containing three different GABA concentrations, 0 (control), 200 mg/kg (GABA200), and 500 mg/kg (GABA500), were fed to Nile tilapia (6.97 ± 0.34 g) for 56 days. The present study found that increasing dietary GABA content could increase the fish growth performance including final body weight, weight gain, specific growth rate, average daily gain, protein efficiency ratio, and feed efficiency compared to the control diet. Interestingly, the feed conversion ratio was improved by dietary GABA supplementation. The antioxidant enzyme activities against ammonia stress of fish fed the GABA diets were significantly higher than the corresponding control group throughout the 96-h ammonia exposure. Moreover, significant increases in digestive enzyme activities including protease, amylase and lipase were found in fish fed the GABA diets. Intestinal morphology analysis revealed increased heights and widths of intestinal villi as well as thickness of the intestinal muscularis in fish fed the GABA diets compared to the control diet. The supplementation of diets with GABA significantly increased the expression level of immune- and growth-related genes. The above results indicate that dietary GABA can modulate the growth, improve their immune response and antioxidant status, gut health and morphology and gene expression of Nile tilapia. Therefore, GABA is a promising feed additive for Nile tilapia aquaculture.

Anxiety and depression: A top-down, bottom-up model of circuit function

A functional interplay of bottom-up and top-down processing allows an individual to appropriately respond to the dynamic environment around them. These processing modalities can be represented as attractor states using a dynamical systems model of the brain. The transition probability to move from one attractor state to another is dependent on the stability, depth, neuromodulatory tone, and tonic changes in plasticity. However, how does the relationship between these states change in disease states, such as anxiety or depression? We describe bottom-up and top-down processing from Marr's computational-algorithmic-implementation perspective to understand depressive and anxious disease states. We illustrate examples of bottom-up processing as basolateral amygdala signaling and projections and top-down processing as medial prefrontal cortex internal signaling and projections. Understanding these internal processing dynamics can help us better model the multifaceted elements of anxiety and depression.

Amygdala activity and amygdala-hippocampus connectivity: Metabolic diseases, dementia, and neuropsychiatric issues

With rapid aging of the population worldwide, the number of people with dementia is dramatically increasing. Some studies have emphasized that metabolic syndrome, which includes obesity and diabetes, leads to increased risks of dementia and cognitive decline. Factors such as insulin resistance, hyperglycemia, high blood pressure, dyslipidemia, and central obesity in metabolic syndrome are associated with synaptic failure, neuroinflammation, and imbalanced neurotransmitter levels, leading to the progression of dementia. Due to the positive correlation between diabetes and dementia, some studies have called it "type 3 diabetes". Recently, the number of patients with cognitive decline due to metabolic imbalances has considerably increased. In addition, recent studies have reported that neuropsychiatric issues such as anxiety, depressive behavior, and impaired attention are common factors in patients with metabolic disease and those with dementia. In the central nervous system (CNS), the amygdala is a central region that regulates emotional memory, mood disorders, anxiety, attention, and cognitive function. The connectivity of the amygdala with other brain regions, such as the hippocampus, and the activity of the amygdala contribute to diverse neuropathological and neuropsychiatric issues. Thus, this review summarizes the significant consequences of the critical roles of amygdala connectivity in both metabolic syndromes and dementia. Further studies on amygdala function in metabolic imbalance-related dementia are needed to treat neuropsychiatric problems in patients with this type of dementia.

Epigenetic mechanisms underlying stress-induced visceral pain: Resilience versus vulnerability in a two-hit model of early life stress and chronic adult stress

BACKGROUND

Women with a history of early life stress (ELS) have a higher risk of developing irritable bowel syndrome (IBS). In addition, chronic stress in adulthood can exacerbate IBS symptoms such as abdominal pain due to visceral hypersensitivity. We previously showed that sex and the predictability of ELS determine whether rats develop visceral hypersensitivity in adulthood. In female rats, unpredictable ELS confers vulnerability and results in visceral hypersensitivity, whereas predictable ELS induces resilience and does not induce visceral hypersensitivity in adulthood. However, this resilience is lost after exposure to chronic stress in adulthood leading to an exacerbation of visceral hypersensitivity. Evidence suggests that changes in histone acetylation at the promoter regions of glucocorticoid receptor (GR) and corticotrophin-releasing factor (CRF) in the central nucleus of the amygdala (CeA) underlie stress-induced visceral hypersensitivity. Here, we aimed to investigate the role of histone acetylation in the CeA on visceral hypersensitivity in a two-hit model of ELS followed by chronic stress in adulthood.

METHODS

Male and female neonatal rats were exposed to unpredictable, predictable ELS, or odor only (no stress control) from postnatal days 8 to 12. In adulthood, rats underwent stereotaxic implantation of indwelling cannulas. Rats were exposed to chronic water avoidance stress (WAS, 1 h/day for 7 days) or SHAM stress and received infusions of vehicle, the histone deacetylase inhibitor trichostatin A (TSA) or the histone acetyltransferase inhibitor garcinol (GAR) after each WAS session. 24 h after the final infusion, visceral sensitivity was assessed and the CeA was removed for molecular experiments.

RESULTS

In the two-hit model (ELS + WAS), female rats previously exposed to predictable ELS, showed a significant reduction in histone 3 lysine 9 (H3K9) acetylation at the GR promoter and a significant increase in H3K9 acetylation at the CRF promoter. These epigenetic changes were associated with changes in GR and CRF mRNA expression in the CeA and an exacerbation of stress-induced visceral hypersensitivity in female animals. TSA infusions in the CeA attenuated the exacerbated stress-induced visceral hypersensitivity, whereas GAR infusions only partially ameliorated ELS+WAS induced visceral hypersensitivity.

CONCLUSION

The two-hit model of ELS followed by WAS in adulthood revealed that epigenetic dysregulation occurs after exposure to stress in two important periods of life and contributes to the development of visceral hypersensitivity. These aberrant underlying epigenetic changes may explain the exacerbation of stress-induced abdominal pain in IBS patients.

Transcriptomic Mapping of Neurotoxicity Pathways in the Rat Brain in Response to Intraventricular Polymyxin B

Intraventricular or intrathecal administration of polymyxins are increasingly used to treat multidrug-resistant (MDR) Gram-negative bacteria caused infections in the central nervous system (CNS). However, our limited knowledge of the mechanisms underpinning polymyxin-induced neurotoxicity significantly hinders the development of safe and efficacious polymyxin dosing regimens. To this end, we conducted transcriptomic analyses of the rat brain and spinal cord 1 h following intracerebroventricular administration of polymyxin B into rat lateral ventricle at a clinically relevant dose (0.5 mg/kg). Following the treatment, 66 differentially expressed genes (DEGs) were identified in the brain transcriptome while none for the spinal cord (FDR ≤ 0.05, fold-change ≥ 1.5). DEGs were enriched in signaling pathways associated with hormones and neurotransmitters, including dopamine and (nor)epinephrine. Notably, the expression levels of Slc6a3 and Gabra6 were decreased by 20-fold and 4.3-fold, respectively, likely resulting in major perturbations of dopamine and γ-aminobutyric acid signaling in the brain. Mass spectrometry imaging of brain sections revealed a distinct pattern of polymyxin B distribution with the majority accumulating in the injection-side lateral ventricle and subsequently into third and fourth ventricles. Polymyxin B was not detectable in the left lateral ventricle or brain tissue. Electrophysiological measurements on primary cultured rat neurons revealed a large inward current and significant membrane leakage following polymyxin B treatment. Our work demonstrates, for the first time, the key CNS signaling pathways associated with polymyxin neurotoxicity. This mechanistic insight combined with pharmacokinetic/pharmacodynamic dosing strategies will help guide the design of safe and effective intraventricular/intrathecal polymyxin treatment regimens for CNS infections caused by MDR Gram-negative pathogens.

Regulation of the central amygdala on intestinal motility and behavior via the lateral hypothalamus in irritable bowel syndrome model mice

BACKGROUND

Impaired bidirectional communication between the gastrointestinal tract and the central nervous system (CNS) is closely related to the development of irritable bowel syndrome (IBS). Studies in patients with IBS have also shown significant activation of the hypothalamus and amygdala. However, how neural circuits of the CNS participate in and process the emotional and intestinal disorders of IBS remains unclear.

METHODS

The GABAergic neural pathway projecting from the central amygdala (CeA) to the lateral hypothalamus (LHA) in mice was investigated by retrograde tracking combined with fluorescence immunohistochemistry. Anxiety, depression-like behavior, and intestinal motility were observed in the water-immersion restraint stress group and the control group. Furthermore, the effects of the chemogenetic activation of the GABAergic neural pathway of CeA-LHA on behavior and intestinal motility, as well as the co-expression of orexin-A and c-Fos in the LHA, were explored.

KEY RESULTS

In our study, Fluoro-Gold retrograde tracking combined with fluorescence immunohistochemistry showed that GABAergic neurons in the CeA were projected to the LHA. The microinjection of the gamma-aminobutyric acid (GABA) receptor antagonist into the LHA relieved anxiety, depression-like behavior, and intestinal motility disorder in the IBS mice. The chemogenetic activation of GABAergic neurons in the CeA-LHA pathway led to anxiety, depression-like behavior, and intestinal motility disorder. In addition, GABAergic neurons in the CeA-LHA pathway inhibited the expression of orexin-A in the LHA, and orexin-A was co-expressed with GABAA receptors.

CONCLUSIONS & INFERENCES

The CeA-LHA GABAergic pathway might participate in the occurrence and development of IBS by regulating orexin-A neurons.

Neonatal inflammation increases hippocampal KCC2 expression through methylation-mediated TGF-β1 downregulation leading to impaired hippocampal cognitive function and synaptic plasticity in adult mice

The mechanisms by which neonatal inflammation leads to cognitive deficits in adulthood remain poorly understood. Inhibitory GABAergic synaptic transmission plays a vital role in controlling learning, memory and synaptic plasticity. Since early-life inflammation has been reported to adversely affect the GABAergic synaptic transmission, the aim of this study was to investigate whether and how neonatal inflammation affects GABAergic synaptic transmission resulting in cognitive impairment. Neonatal mice received a daily subcutaneous injection of lipopolysaccharide (LPS, 50 μg/kg) or saline on postnatal days 3-5. It was found that blocking GABAergic synaptic transmission reversed the deficit in hippocampus-dependent memory or the induction failure of long-term potentiation in the dorsal CA1 in adult LPS mice. An increase of mIPSCs amplitude was further detected in adult LPS mice indicative of postsynaptic potentiation of GABAergic transmission. Additionally, neonatal LPS resulted in the increased expression and function of K⁺-Cl^--cotransporter 2 (KCC2) and the decreased expression of transforming growth factor-beta 1 (TGF-β1) in the dorsal CA1 during adulthood. The local TGF-β1 overexpression improved KCC2 expression and function, synaptic plasticity and memory of adult LPS mice. Adult LPS mice show hypermethylation of TGFb1 promoter and negatively correlate with reduced TGF-β1 transcripts. 5-Aza-deoxycytidine restored the changes in TGFb1 promoter methylation and TGF-β1 expression. Altogether, the results suggest that hypermethylation-induced reduction of TGF-β1 leads to enhanced GABAergic synaptic inhibition through increased KCC2 expression, which is a underlying mechanism of neonatal inflammation-induced hippocampus-dependent memory impairment in adult mice.

Hormonal contraceptives and the brain: A systematic review on 60 years of neuroimaging, EEG, and biochemical studies in humans and animals

Hormonal contraception has been widely prescribed for decades. Although safety and efficacy are well-established, much uncertainty remains regarding brain effects of hormonal contraception. We systematically review human and animal studies on the brain effects of hormonal contraception which employed neuroimaging techniques such as MRI, PET and EEG, as well as animal studies which reported on neurotransmitter and other brain biochemical effects. We screened 1001 articles and ultimately extracted data from 70, comprising 51 human and 19 animal studies. Of note, there were no animal studies which employed structural or functional MRI, MRS or PET. In summary, our review shows hormonal contraceptive associations with changes in the brain have been documented. Many questions remain and more studies are needed to describe the effects of hormonal contraception on the brain.

Early Chronic Stress Induced Changes within the Locus Coeruleus in Sporadic Alzheimer's Disease

Chronic exposure to stress throughout the lifespan has been the focus of many studies on Alzheimer's disease (AD) because of the similarities between the biological mechanisms involved in chronic stress and the pathophysiology of AD. In fact, the earliest abnormality associated with the disease is the presence of phosphorylated tau protein in locus coeruleus neurons, a brain structure highly responsive to stress and perceived threat. Here, we introduce allostatic load as a useful concept for understanding many of the complex, interacting neuropathological changes involved in the AD degenerative process. In response to chronic stress, aberrant tau proteins that begin to accumulate within the locus coeruleus decades prior to symptom onset appear to represent a primary pathological event in the AD cascade, triggering a wide range of interacting brain changes involving neuronal excitotoxicity, endocrine alterations, inflammation, oxidative stress, and amyloid plaque exacerbation. While it is acknowledged that stress will not necessarily be the major precipitating factor in all cases, early tau-induced changes within the locus coeruleus-norepinephrine pathway suggests that a therapeutic window might exist for preventative measures aimed at managing stress and restoring balance within the HPA axis.

Does folic acid supplementation have a positive effect on improving memory? A systematic review and meta-analysis of randomized controlled trials

Introduction

The results of randomized controlled trials (RCTs) on the effect of folic acid supplementation on memory status due to various heterogeneity, dosage, duration, and cognitive function assessments were inconclusive. Therefore, we have performed a systematic review and meta-analysis to investigate the effect of folic acid supplementation on memory in RCTs.

Method

Comprehensive computerized systematic searches were conducted throughout Scopus, PubMed/Medline, and Google Scholar from inception until February 2022 to investigate the effect of folic acid supplementation memory levels in RCTs. The standardized mean difference (SMD) and 95% confidence interval (CIs) were used to estimate the overall effect size using random-effects meta-analyses.

Results

The overall results of nine trials with 641 participants, revealed that folic acid supplementation did not significantly change memory score compared to placebo (SMD: 0.12; 95% CI: -0.17, 0.40, p = 0.418; I 2 = 62.6%). However, subgroup analyses showed that supplementation with folic acid had favorable effects on memory levels considering the following conditions: (1) doses lower than 1 mg/day, (2) treatment lasting more than 6 months, (3) conducted in eastern countries, and (4) in participants equal to or older than 70 years old. The dose-response analysis suggested a significant favorable effect on memory status at doses of 6-11 mg/d and a significant decline at doses of 17-20 mg/d.

Discussion

Although we did not find a significant effect of folic acid supplementation on memory, there were some suggestions of beneficial effects in the subgroup analyses.

The Effect of Dracocephalum Extract on Sleep Quality in Post-Menopausal Women: A Randomized Placebo-Controlled Trial

Objective: Sleep disturbance is one of the most prevalent problems in post-menopausal females. The current research intended to evaluate the effects of Dracocephalum on sleep disorder in post-menopausal females. Method : The current study is a randomized, double-blind controlled trial, in which 110 post-menopausal women were randomly allocated to Dracocephalum or placebo groups. The intervention group took Dracocephalum capsules containing 250 mg Dracocephalum extract twice daily for one month. While, the placebo group took the same capsule containing 250 mg of starch twice daily for one month. Pittsburgh Sleep Quality Index was completed by the participants of both groups before and after the treatment and the data obtained were analyzed with Chi-square, paired and independent t-test in SPSS (version 20). Results: The mean score of sleep quality before and after the treatment was 12.69 ± 3.98 and 8.58 ± 1.97 in the treatment group, respectively. Also, the score of sleep quality in the placebo group was 13.48 ± 2.60 and 11.21 ± 2.74 at the beginning and end of the research, respectively. The symptoms of sleep disorder in the intervention group significantly improved after the treatment (P < 0.001), while this was not the case with the placebo group (P = 0.155). Besides, there was a significant difference between the two groups in the mean score of sleep quality after the treatment (P = 0.012). Conclusion: Dracocephalum extracts are effective in reducing symptoms of sleep disorders in post-menopausal women.

Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials

Clinical trial studies revealed conflicting results on the effect of Ashwagandha extract on anxiety and stress. Therefore, we aimed to evaluate the effect of Ashwagandha supplementation on anxiety as well as stress. A systematic search was performed in PubMed/Medline, Scopus, and Google Scholar from inception until December 2021. We included randomized clinical trials (RCTs) that investigate the effect of Ashwagandha extract on anxiety and stress. The overall effect size was pooled by random-effects model and the standardized mean difference (SMD) and 95% confidence interval (CIs) for outcomes were applied. Overall, 12 eligible papers with a total sample size of 1,002 participants and age range between 25 and 48 years were included in the current systematic review and meta-analysis. We found that Ashwagandha supplementation significantly reduced anxiety (SMD: -1.55, 95% CI: -2.37, -0.74; p = .005; I²  = 93.8%) and stress level (SMD: -1.75; 95% CI: -2.29, -1.22; p = .005; I²  = 83.1%) compared to the placebo. Additionally, the non-linear dose-response analysis indicated a favorable effect of Ashwagandha supplementation on anxiety until 12,000 mg/d and stress at dose of 300-600 mg/d. Finally, we identified that the certainty of the evidence was low for both outcomes. The current systematic review and dose-response meta-analysis of RCTs revealed a beneficial effect in both stress and anxiety following Ashwagandha supplementation. However, further high-quality studies are needed to firmly establish the clinical efficacy of the plant.

Pharmacotherapeutic management of insomnia and effects on sleep processes, neural plasticity, and brain systems modulating stress: A narrative review

Introduction

Insomnia is a stress-related sleep disorder, may favor a state of allostatic overload impairing brain neuroplasticity, stress immune and endocrine pathways, and may contribute to mental and physical disorders. In this framework, assessing and targeting insomnia is of importance.

Aim

Since maladaptive neuroplasticity and allostatic overload are hypothesized to be related to GABAergic alterations, compounds targeting GABA may play a key role. Accordingly, the aim of this review was to discuss the effect of GABAA receptor agonists, short-medium acting hypnotic benzodiazepines and the so called Z-drugs, at a molecular level.

Method

Literature searches were done according to PRISMA guidelines. Several combinations of terms were used such as “hypnotic benzodiazepines” or “brotizolam,” or “lormetazepam” or “temazepam” or “triazolam” or “zolpidem” or “zopiclone” or “zaleplon” or “eszopiclone” and “insomnia” and “effects on sleep” and “effect on brain plasticity” and “effect on stress system”. Given the complexity and heterogeneity of existing literature, we ended up with a narrative review.

Results

Among short-medium acting compounds, triazolam has been the most studied and may regulate the stress system at central and peripheral levels. Among Z-drugs eszopiclone may regulate the stress system. Some compounds may produce more “physiological” sleep such as brotizolam, triazolam, and eszopiclone and probably may not impair sleep processes and related neural plasticity. In particular, triazolam, eszopiclone, and zaleplon studied in vivo in animal models did not alter neuroplasticity.

Conclusion

Current models of insomnia may lead us to revise the way in which we use hypnotic compounds in clinical practice. Specifically, compounds should target sleep processes, the stress system, and sustain neural plasticity. In this framework, among the short/medium acting hypnotic benzodiazepines, triazolam has been the most studied compound while among the Z-drugs eszopiclone has demonstrated interesting effects. Both offer potential new insight for treating insomnia.

Allosteric Modulators of Metabotropic Glutamate Receptors as Novel Therapeutics for Neuropsychiatric Disease

Metabotropic glutamate (mGlu) receptors, a family of G-protein-coupled receptors, have been identified as novel therapeutic targets based on extensive research supporting their diverse contributions to cell signaling and physiology throughout the nervous system and important roles in regulating complex behaviors, such as cognition, reward, and movement. Thus, targeting mGlu receptors may be a promising strategy for the treatment of several brain disorders. Ongoing advances in the discovery of subtype-selective allosteric modulators for mGlu receptors has provided an unprecedented opportunity for highly specific modulation of signaling by individual mGlu receptor subtypes in the brain by targeting sites distinct from orthosteric or endogenous ligand binding sites on mGlu receptors. These pharmacological agents provide the unparalleled opportunity to selectively regulate neuronal excitability, synaptic transmission, and subsequent behavioral output pertinent to many brain disorders. Here, we review preclinical and clinical evidence supporting the utility of mGlu receptor allosteric modulators as novel therapeutic approaches to treat neuropsychiatric diseases, such as schizophrenia, substance use disorders, and stress-related disorders.

Age-Dependent Reduction in the Expression Levels of Genes Involved in Progressive Myoclonus Epilepsy Correlates with Increased Neuroinflammation and Seizure Susceptibility in Mouse Models

Brain aging is characterized by a gradual decline in cellular homeostatic processes, thereby losing the ability to respond to physiological stress. At the anatomical level, the aged brain is characterized by degenerating neurons, proteinaceous plaques and tangles, intracellular deposition of glycogen, and elevated neuroinflammation. Intriguingly, such age-associated changes are also seen in neurodegenerative disorders suggesting that an accelerated aging process could be one of the contributory factors for the disease phenotype. Amongst these, the genetic forms of progressive myoclonus epilepsy (PME), resulting from loss-of-function mutations in genes, manifest symptoms that are common to age-associated disorders, and genes mutated in PME are involved in the cellular homeostatic processes. Intriguingly, the incidence and/or onset of epileptic seizures are known to increase with age, suggesting that physiological changes in the aged brain might contribute to increased susceptibility to seizures. We, therefore, hypothesized that the expression level of genes implicated in PME might decrease with age, thereby leading to a compromised neuronal response towards physiological stress and hence neuroinflammation in the aging brain. Using mice models, we demonstrate here that the expression level of PME genes shows an inverse correlation with age, neuroinflammation, and compromised heat shock response. We further show that the pharmacological suppression of neuroinflammation ameliorates seizure susceptibility in aged animals as well as in animal models for a PME. Taken together, our results indicate a functional role for the PME genes in normal brain aging and that neuroinflammation could be a major contributory player in susceptibility to seizures.

Chronic hypothalamic-pituitary-adrenal axis disruption alters glutamate homeostasis and neural responses to stress in male C57Bl6/N mice

It is now well-established that stress elicits brain- and body-wide changes in physiology and has significant impacts on many aspects of health. The hypothalamic-pituitary-adrenal (HPA) axis is the major neuroendocrine system mediating the integrated response to stress. Appropriate engagement and termination of HPA activity enhances survival and optimizes physiological and behavioral responses to stress, while dysfunction of this system is linked to negative health outcomes such as depression, anxiety, and post-traumatic stress disorder. Glutamate signaling plays a large role in the transmission of stress-related information throughout the brain. Furthermore, aberrant glutamate signaling has negative consequences for neural plasticity and synaptic function and is linked to stress-related pathology. However, the connection between HPA dysfunction and glutamate signaling is not fully understood. We tested how HPA axis dysfunction (using low dose chronic corticosterone in the drinking water) affects glutamate homeostasis and neural responses under baseline and acute stress in male C57BL/6N mice. Using laser microdissection and transcriptomic analyses, we show that chronic disruption of the HPA axis alters the expression of genes related to glutamate signaling in the medial prefrontal cortex (mPFC), hippocampus, and amygdala. While neural responses to stress (as measured by FOS) in the hippocampus and amygdala were not affected in our model of HPA dysfunction, we observed an exaggerated response to stress in the mPFC. To further probe this we undertook in vivo biosensor measurements of the dynamics of extracellular glutamate responses to stress in the mPFC in real-time, and found glutamate dynamics in the mPFC were significantly altered by chronic HPA dysfunction. Together, these findings support the hypothesis that chronic HPA axis dysfunction alters glutamatergic signaling in regions known to regulate emotional behavior, providing more evidence linking HPA dysfunction and stress vulnerability.

Influence of a Polyherbal Choline Source in Dogs: Body Weight Changes, Blood Metabolites, and Gene Expression

Choline chloride is used to provide choline in dog foods; however, in other domestic species, it has been replaced with a polyherbal containing phosphatidylcholine. A polyherbal containing Achyrantes aspera, Trachyspermum ammi, Citrullus colocynthis, Andrographis paniculata, and Azadirachta indica was evaluated in adult dogs through body weight changes, subcutaneous fat thickness, blood metabolites, and gene expression. Forty dogs (4.6 ± 1.6 years old) who were individually housed in concrete kennels were randomly assigned to the following treatments: unsupplemented diet (377 mg choline/kg), choline chloride (3850 mg/kg equivalent to 2000 mg choline/kg diet), and polyherbal (200, 400, and 800 mg/kg) for 60 days. Blood samples were collected on day 59 for biochemistry, biometry, and gene expression analysis through microarray assays. Intake, final body weight, and weight changes were similar for the two choline sources. Feed intake variation among dogs (p = 0.01) and dorsal fat (p = 0.03) showed a quadratic response to herbal choline. Dogs that received the polyherbal diet had reduced blood cholesterol levels (Quadratic, p = 0.02). The gene ontology analysis indicated that 15 biological processes were modified (p ≤ 0.05) with implications for preventing cardiovascular and metabolic diseases, cancer prevention, inflammatory and immune response, and behavior and cognitive process. According to these results that were observed in a 60 day trial, the polyherbal form could replace choline chloride in dog diets at a concentration of 400 mg/kg.

Impact of stress on inhibitory neuronal circuits, our tribute to Bruce McEwen

This manuscript is dedicated to the memory of Bruce S. McEwen, to commemorate the impact he had on how we understand stress and neuronal plasticity, and the profound influence he exerted on our scientific careers. The focus of this review is the impact of stressors on inhibitory circuits, particularly those of the limbic system, but we also consider other regions affected by these adverse experiences. We revise the effects of acute and chronic stress during different stages of development and lifespan, taking into account the influence of the sex of the animals. We review first the influence of stress on the physiology of inhibitory neurons and on the expression of molecules related directly to GABAergic neurotransmission, and then focus on specific interneuron subpopulations, particularly on parvalbumin and somatostatin expressing cells. Then we analyze the effects of stress on molecules and structures related to the plasticity of inhibitory neurons: the polysialylated form of the neural cell adhesion molecule and perineuronal nets. Finally, we review the potential of antidepressants or environmental manipulations to revert the effects of stress on inhibitory circuits.

Biology of cyclooxygenase-2: An application in depression therapeutics

Depressive Disorder is a common mood disorder or affective disorder that is dominated by depressed mood. It is characterized by a high incidence and recurrence. The onset of depression is related to genetic, biological and psychosocial factors. However, the pathogenesis is still unclear. In recent years, there has been an increasing amount of research on the inflammatory hypothesis of depression, in which cyclo-oxygen-ase 2 (COX-2), a pro-inflammatory cytokine, is closely associated with depression. A variety of chemical drugs and natural products have been found to exert therapeutic effects by modulating COX-2 levels. This paper summarizes the relationship between COX-2 and depression in terms of neuroinflammation, intestinal flora, neurotransmitters, HPA axis, mitochondrial dysfunction and hippocampal neuronal damage, which can provide a reference for further preventive control, clinical treatment and scientific research on depression.

GABAA(δ) receptor hypofunction in the amygdala-hippocampal circuit underlies stress-induced anxiety

Dysregulated GABAergic inhibition in the amygdala has long been implicated in stress-related neuropsychiatric disorders. However, the molecular and circuit mechanisms underlying the dysregulation remain elusive. Here, by using a mouse model of chronic social defeat stress (CSDS), we observed that the dysregulation varied drastically across individual projection neurons (PNs) in the basolateral amygdala (BLA), one of the kernel amygdala subregions critical for stress coping. While persistently reducing the extrasynaptic GABA_A receptor (GABA_AR)-mediated tonic current in the BLA PNs projecting to the ventral hippocampus (BLA → vHPC PNs), CSDS increased the current in those projecting to the anterodorsal bed nucleus of stria terminalis (BLA → adBNST PNs), suggesting projection-based dysregulation of tonic inhibition in BLA PNs by CSDS. Transcriptional and electrophysiological analysis revealed that the opposite CSDS influences were mediated by loss- and gain-of-function of δ-containing GABA_ARs (GABA_A(δ)Rs) in BLA → vHPC and BLA → adBNST PNs, respectively. Importantly, it was the lost inhibition in the former population but not the augmentation in the latter population that correlated with the increased anxiety-like behavior in CSDS mice. Virally mediated maintenance of GABA_A(δ)R currents in BLA → vHPC PNs occluded CSDS-induced anxiety-like behavior. These findings clarify the molecular substrate for the dysregulated GABAergic inhibition in amygdala circuits for stress-associated psychopathology.

A terrifying sound stress inhibits hippocampal neurogenesis in the adult male mice

Stress impairs hippocampal neurogenesis. The traditional animal model of stress contains a mixture of physical and psychological stress factors. This leads to difficulty in the evaluation of the effect of pure psychological stress on neurogenesis. In this study, we investigated the effect of pure psychological stress on hippocampal neurogenesis. The pure psychological stress model and the mixed stress model were carried out by terrifying sound and restraint, respectively. The open field test showed that restraint treatment improved the general locomotor activity levels, while terrifying sound treatment had opposite effects. Compared with a normal condition, both terrifying sound stimulation and restraint treatment significantly decreased the number of BrdU and Ki-67 and reduced the positive rate of SOX2/GFAP in the hippocampus. These phenomena indicated that pure psychological stress could decrease the number of neural stem cells and inhibit cell proliferation in the hippocampus of a mouse. Furthermore, compared with the restraint treatment, the neurotransmitters including norepinephrine (NE), 5-hydroxytryptamine (5-HT), and gamma-aminobutyric acid (GABA) had not been affected drastically by terrifying sound stimulation. Our results suggest that the terrifying sound stimulation can be considered as a novel and effective pure psychological stress animal model for the further research on the hippocampus.

GABA System in Depression: Impact on Pathophysiology and Psychopharmacology

BACKGROUND

The pathophysiology of major depressive disorder (MDD), one of the major causes of worldwide disability, is still largely unclear, despite the increasing data reporting evidence of multiple alterations of different systems. Recently, there was a renewed interest in the signalling of gamma aminobutyric acid (GABA) - the main inhibitory neurotransmitter.

OBJECTIVE

The aim of this study was to review and comment on the available literature about the involvement of GABA in MDD, as well as on novel GABAergic compounds possibly useful as antidepressants.

METHODS

We carried out a narrative review through Pubmed, Google Scholar and Scopus, by using specific keywords.

RESULTS

The results, derived from various research tools, strongly support the presence of a deficiency of the GABA system in MDD, which appears to be restored by common antidepressant treatments. More recent publications would indicate the complex interactions between GABA and all the other processes involved in MDD, such as monoamine neurotransmission, hypothalamus-pituitary adrenal axis functioning, neurotrophism, and immune response. Taken together, all these findings seem to further support the complexity of the pathophysiology of MDD, possibly reflecting the heterogeneity of the clinical pictures.

CONCLUSION

Although further data are necessary to support the specificity of GABA deficiency in MDD, the available findings would suggest that novel GABAergic compounds might constitute innovative therapeutic strategies in MDD.

Alpha-synuclein pathology, microgliosis, and parvalbumin neuron loss in the amygdala associated with enhanced fear in the Thy1-aSyn model of Parkinson's disease

In Parkinson's disease (PD), the second most common neurodegenerative disorder, non-motor symptoms often precede the development of debilitating motor symptoms and present a severe impact on the quality of life. Lewy bodies containing misfolded α-synuclein progressively develop in neurons throughout the peripheral and central nervous system, which may be correlated with the early development of non-motor symptoms. Among those, increased fear and anxiety is frequent in PD and thought to result from pathology outside the dopaminergic system, which has been the focus of symptomatic treatment to alleviate motor symptoms. Alpha-synuclein accumulation has been reported in the amygdala of PD patients, a brain region critically involved in fear and anxiety. Here we asked whether α-synuclein overexpression alone is sufficient to induce an enhanced fear phenotype in vivo and which pathological mechanisms are involved. Transgenic mice expressing human wild-type α-synuclein (Thy1-aSyn), a well-established model of PD, were subjected to fear conditioning followed by extinction and then tested for extinction memory retention followed by histopathological analysis. Thy1-aSyn mice showed enhanced tone fear across acquisition and extinction compared to wild-type littermates, as well as a trend to less retention of fear extinction. Immunohistochemical analysis of the basolateral nucleus of the amygdala, a nucleus critically involved in tone fear learning, revealed extensive α-synuclein pathology, with accumulation, phosphorylation, and aggregation of α-synuclein in transgenic mice. This pathology was accompanied by microgliosis and parvalbumin neuron loss in this nucleus, which could explain the enhanced fear phenotype. Importantly, this non-motor phenotype was detected in the pre-clinical phase, prior to dopamine loss in Thy1-aSyn mice, thus replicating observations in patients. Results obtained in this study suggest a possible mechanism by which increased anxiety and maladaptive fear processing may occur in PD, opening a door for therapeutic options and further early biomarker research.

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

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

How stress physically re-shapes the brain: Impact on brain cell shapes, numbers and connections in psychiatric disorders

Severe stress is among the most robust risk factors for the development of psychiatric disorders. Imaging studies indicate that life stress is integral to shaping the human brain, especially regions involved in processing the stress response. Although this is likely underpinned by changes to the cytoarchitecture of cellular networks in the brain, we are yet to clearly understand how these define a role for stress in human psychopathology. In this review, we consolidate evidence of macro-structural morphometric changes and the cellular mechanisms that likely underlie them. Focusing on stress-sensitive regions of the brain, we illustrate how stress throughout life may lead to persistent remodelling of the both neurons and glia in cellular networks and how these may lead to psychopathology. We support that greater translation of cellular alterations to human cohorts will support parsing the psychological sequalae of severe stress and improve our understanding of how stress shapes the human brain. This will remain a critical step for improving treatment interventions and prevention outcomes.

Differential efferent projections of GABAergic neurons in the basolateral and central nucleus of amygdala in mice

The Basolateral amygdala (BLA) and central nucleus of the amygdala (CEA) have been proved to play a key role in the control of anxiety, stress and fear-related behaviors. BLA is a cortex-like complex consisting of both γ-aminobutyric acidergic (GABAergic) interneurons and glutamatergic neurons. The CEA is a striatum-like output of the amygdala, consisting almost exclusively of GABAergic medium spiny neurons. In this study, we explored the morphology and axonal projections of the GABAergic neurons in BLA and CEA, using conditional anterograde axonal tracing, immunohistochemistry, and VGAT-Cre transgenic mice to further understand their functional roles. We found that the axonal projections of GABAergic neurons from the BLA mainly distributed to the forebrain, whilst GABAergic neurons from the CEA distributed to the forebrain, midbrain and brainstem. In the forebrain, the axonal projections of GABAergic neurons from the BLA projected to the anterior olfactory nucleus, the cerebral cortex, the septum, the striatum, the thalamus, the amygdala and the hippocampus. The axonal projections of GABAergic neurons from the CEA distributed to the nuclei of the prefrontal cortex, the bed nucleus of the stria terminalis, the hypothalamus and the thalamus. In the midbrain and brainstem, the axonal projections of GABAergic neurons from the CEA were found in the periaqueductal gray, the substantia nigra, and the locus coeruleus. These data reveal the neuroanatomical basis for exploring the function of GABAergic neurons in the BLA and CEA, particularly during the processing of fear-related behavior.

An analog of psychedelics restores functional neural circuits disrupted by unpredictable stress

Psychological stress affects a wide spectrum of brain functions and poses risks for many mental disorders. However, effective therapeutics to alleviate or revert its deleterious effects are lacking. A recently synthesized psychedelic analog tabernanthalog (TBG) has demonstrated anti-addictive and antidepressant potential. Whether TBG can rescue stress-induced affective, sensory, and cognitive deficits, and how it may achieve such effects by modulating neural circuits, remain unknown. Here we show that in mice exposed to unpredictable mild stress (UMS), administration of a single dose of TBG decreases their anxiety level and rescues deficits in sensory processing as well as in cognitive flexibility. Post-stress TBG treatment promotes the regrowth of excitatory neuron dendritic spines lost during UMS, decreases the baseline neuronal activity, and enhances whisking-modulation of neuronal activity in the somatosensory cortex. Moreover, calcium imaging in head-fixed mice performing a whisker-dependent texture discrimination task shows that novel textures elicit responses from a greater proportion of neurons in the somatosensory cortex than do familiar textures. Such differential response is diminished by UMS and is restored by TBG. Together, our study reveals the effects of UMS on cortical neuronal circuit activity patterns and demonstrate that TBG combats the detrimental effects of stress by modulating basal and stimulus-dependent neural activity in cortical networks.

Intra-amygdala metaplasticity modulation of fear extinction learning

The amygdala is a key brain region involved in emotional memory formation. It is also responsible for memory modulation in other brain areas. Under extreme conditions, amygdala modulation may lead to the generation of abnormal plasticity and trauma-related psychopathologies. However, the amygdala itself is a dynamic brain region, which is amenable to long-term plasticity and is affected by emotional experiences. These alterations may modify the way the amygdala modulates activity and plasticity in other related brain regions, which in turn may alter the animal's response to subsequent challenges in what could be termed as "Behavioral metaplasticity."Because of the reciprocal interactions between the amygdala and other emotion processing regions, such as the medial prefrontal cortex (mPFC) or the hippocampus, experience-induced intra-amygdala metaplasticity could lead to alterations in mPFC-dependent or hippocampus-dependent behaviors. While initiated by alterations within the basolateral amygdala (BLA), such alterations in other brain regions may come to be independent of BLA modulation, thus establishing what may be termed "Trans-regional metaplasticity." In this article, we review evidence supporting the notions of intra-BLA metaplasticity and how this may develop into "Trans-regional metaplasticity." Future research is needed to understand how such dynamic metaplastic alterations contribute to developing psychopathologies, and how this knowledge may be translated into promoting novel interventions in psychopathologies associated with fear, stress, and trauma.

Anxiolytic activity of Psidium guajava in mice subjected to chronic restraint stress and effect on neurotransmitters in brain

The anxiolytic activity of Psidium guajava L. leaf ethanolic extract (PLE) and its effect on neurotransmitter systems was investigated. PLE, extracted using Soxhlet apparatus, was subjected to preliminary qualitative and quantitative (flavonoids and phenols) analyses. The anxiolytic activity at 100, 200, and 400 mg/Kg doses were assessed in mice using elevated plus maze (EPM) and light/dark transition (LDT) test models on days 1 and 16. Neurotransmitters such as monoamines (serotonin, norepinephrine, and dopamine), γ-aminobutyric acid (GABA), and glutamate were estimated in different regions of the brain (cortex, hippocampus, and cerebellum and brain stem). Phytoconstituents identified using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry were analyzed in silico to evaluate their potential binding mode(s) to GABA_A and 5-HT_1A receptors. Phytochemical studies showed the presence of alkaloids, tannins, flavonoids, saponins, anthraquinone glycosides, carbohydrates, and proteins, whereas total flavonoid and phenol contents were estimated to be 64.96 ± 0.95 and 206.58 ± 1.60 mg/g of dried extract, respectively. PLE treatment significantly enhanced exploratory activity of mice in EPM and LDT models with significant effects on monoamines, GABA and glutamate levels in the brain. The in silico studies suggested the interaction(s) of PLE component(s) with GABA_A /5-HT_1A receptors as a potential mechanism of its anxiolytic activity.

Chronic optogenetic manipulation of basolateral amygdala astrocytes rescues stress-induced anxiety

Chronic exposure to stressors can disrupt normal brain function and induce anxiety-like behavior and neurobiological alterations in the basolateral amygdala (BLA). Here, we showed that unpredictable chronic mild stress (UCMS) induced anxiety-like behavior, lowered glutamatergic neuronal activity and reactive astrocytes in the BLA. Using optogenetic tools, we found that activation of BLA glutamatergic neurons did not rescue anxiety-like behavior in stressed mice. In contrast, however, optogenetic activation of the BLA astrocytes relieved stress-induced anxiety, and, interestingly, chronic optogenetic manipulation fully restored the UCMS-induced behavioral and neurobiological dysfunctions, including anxiety-like behavior, lower c-Fos expression in the BLA, S100 overexpression in the BLA, and higher serum corticosterone concentration. Thus, our findings suggest that chronic manipulation of BLA astrocytes is a potential therapeutic intervention target for pathological anxiety.

Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review

Gamma-aminobutyric acid (GABA) is a non-proteinogenic amino acid and is the main inhibitory neurotransmitter in the mammalian brain. GABA's stress-reducing, and sleep enhancing effects have been established. However, although several human clinical trials have been conducted, results regarding the role of natural and/or biosynthetic oral GABA intake on stress and sleep are mixed. We performed a systematic review to examine whether natural and/or biosynthetic oral GABA intake has an effect on stress and sleep. We systematically searched on PubMed database for studies published up to February 2020 following PRISMA guidelines. Only placebo-controlled human trials that assessed stress, sleep, and related psychophysiological outcomes as a response to natural GABA (i.e., GABA that is present naturally in foods) or biosynthetic GABA (i.e., GABA that is produced via fermentation) intake were included. Fourteen studies met the criteria and were included in the systematic review. Although more studies are needed before any inferences can be made about the efficacy of oral GABA consumption on stress and sleep, results show that there is limited evidence for stress and very limited evidence for sleep benefits of oral GABA intake.

Genome-Wide DNA Methylation and Gene Expression Profiles in Cows Subjected to Different Stress Level as Assessed by Cortisol in Milk

Dairy cattle health, wellbeing and productivity are deeply affected by stress. Its influence on metabolism and immune response is well known, but the underlying epigenetic mechanisms require further investigation. In this study, we compared DNA methylation and gene expression signatures between two dairy cattle populations falling in the high- and low-variant tails of the distribution of milk cortisol concentration (MC), a neuroendocrine marker of stress in dairy cows. Reduced Representation Bisulfite Sequencing was used to obtain a methylation map from blood samples of these animals. The high and low groups exhibited similar amounts of methylated CpGs, while we found differences among non-CpG sites. Significant methylation changes were detected in 248 genes. We also identified significant fold differences in the expression of 324 genes. KEGG and Gene Ontology (GO) analysis showed that genes of both groups act together in several pathways, such as nervous system activity, immune regulatory functions and glucocorticoid metabolism. These preliminary results suggest that, in livestock, cortisol secretion could act as a trigger for epigenetic regulation and that peripheral changes in methylation can provide an insight into central nervous system functions.

Activation of LXRβ Signaling in the Amygdala Confers Anxiolytic Effects Through Rebalancing Excitatory and Inhibitory Neurotransmission upon Acute Stress

The balance of major excitatory (glutamate, Glu) and inhibitory (γ-aminobutyric acid, GABA), named as E/I neurotransmission, is critical for proper information processing. Anxiety-like responses upon stress are accompanied by abnormal alterations in the formation and function of synapses, resulting in the imbalance of E/I neurotransmission in the amygdala. Liver X receptors (LXRs), including LXRα and LXRβ isoforms, are nuclear receptors responsible for regulating central nervous system (CNS) functions besides maintaining metabolic homeostasis. However, little is known about the contribution of LXRs in E/I balance in regulating anxiety-related behaviors induced by stress. In this study, we found stress-induced anxiety led to the expression reduction of LXRβ not LXRα in mice amygdala. GW3965, a dual agonist for both LXRα and LXRβ, alleviated anxiety-like behaviors of stressed mice through activation of LXRβ, confirmed by the knockdown of LXRβ mediated by lentiviral shRNAs in the basolateral amygdala (BLA). This was paralleled by correcting the disequilibrium of E/I neurotransmission in the stressed BLA. Importantly, GW3965 exerted anxiolytic effects by correcting the promoted amplitude and frequency of miniature excitatory postsynaptic current (mEPSC), and augmenting the decreased that of miniature inhibitory postsynaptic current (mIPSC) in the stressed BLA. This suggests that stress-induced anxiety-like behaviors can largely be ascribed to the deficit of LXRβ signaling in E/I neurotransmission in BLA. These findings highlight the deficiency of LXRβ signaling in the amygdala linked to anxiety disorder, and LXRβ activation may represent a potential novel target for anxiety treatment with an alteration in synaptic transmission in the amygdala.

ActivatIon of Calcium binding protein-ir neurons IN MEDIAL AMYGDALA during chemosignal processing

The medial amygdala receives sensory input from chemical signals important in mammalian social communication. As measured by immediate early gene expression, its responses to different chemosignals differ in the spatial patterns of neuronal activation and in the types of cells activated. Medial amygdala projections to basal forebrain contibute to generation of appropriate behavioral responses and GABA neurons are important for these functions, both as interneurons and projection neurons. Here we investigate reponses of male golden-hamster medial amygdala neurons expressing immunoreactivity (-ir) for calbindin (CB), calretinin (CR) and parvalbumin (PV), calcium binding proteins (CBPs) which can distinguish different GABA-ergic neuron types. CB-ir and CR-ir cells both had significant responses to female hamster chemosignals and showed different spatial patterns across medial amygdala. Responses to chemosignals (from unfamiliar females) were significantly reduced in males with sexual experience, compared to naïve males. Medial amygdala did not express PV-ir cells and the adjacent intercalated nucleus, which has been implicated in medial amygdala chemosensory responses did not express any of the CBPs investigated here. This additional evidence for chemosensory specificity in the response of medial amygdala to social chemical signals, in cells characterized by CBP expression, suggests multiple GABA circuit elements may be involved in information processing for behavioral response.

Chronic Stress Oppositely Regulates Tonic Inhibition in Thy1-Expressing and Non-expressing Neurons in Amygdala

Chronic or prolonged exposure to stress ranks among the most important socioenvironmental factors contributing to the development of neuropsychiatric diseases, a process generally associated with loss of inhibitory tone in amygdala. Recent studies have identified distinct neuronal circuits within the basolateral amygdala (BLA) engaged in different emotional processes. However, the potential circuit involved in stress-induced dysregulation of inhibitory tones in BLA remains elusive. Here, a transgenic mouse model expressing yellow fluorescent protein under control of the Thy1 promoter was used to differentiate subpopulations of projection neurons (PNs) within the BLA. We observed that the tonic inhibition in amygdala neurons expressing and not expressing Thy1 (Thy1+/-) was oppositely regulated by chronic social defeat stress (CSDS). In unstressed control mice, the tonic inhibitory currents were significantly stronger in Thy1- PNs than their Thy1+ counterparts. CSDS markedly reduced the currents in Thy1- projection neurons (PNs), but increased that in Thy1+ ones. By contrast, CSDS failed to affect both the phasic A-type γ-aminobutyric acid receptor (GABA_AR) currents and GABA_BR currents in these two PN populations. Moreover, chronic corticosterone administration was sufficient to mimic the effect of CSDS on the tonic inhibition of Thy1+ and Thy1- PNs. As a consequence, the suppression of tonic GABA_AR currents on the excitability of Thy1- PNs was weakened by CSDS, but enhanced in Thy1+ PNs. The differential regulation of chronic stress on the tonic inhibition in Thy1+ and Thy1- neurons may orchestrate cell-specific adaptation of amygdala neurons to chronic stress.