Chronic social stress: effects on limbic brain structures

Personal Mastery Attenuates the Association between Greater Perceived Discrimination and Lower Amygdala and Anterior Hippocampal Volume in a Diverse Sample of Older Adults

There is limited research investigating whether perceived discrimination influences brain structures that subserve episodic memory, namely the hippocampus and amygdala. Our rationale for examining these regions build on their known sensitivity to stress and functional differences along the long-axis of the hippocampus, with the anterior hippocampus and amygdala implicated in emotional and stress regulation. We defined perceived discrimination as the unfair treatment of one group by a dominant social group without the agency to respond to the event. A potential moderator of perceived discrimination is personal mastery, which we operationally defined as personal agency. Our primary goals were to determine whether perceived discrimination correlated with amygdala and anterior hippocampal volume, and if personal mastery moderated these relationships. Using FreeSurfer 7.1.0, we processed T1-weighted images to extract bilateral amygdala and hippocampal volumes. Discrimination and personal mastery were assessed via self-report (using the Experiences of Discrimination and Sense of Control questionnaires, respectively). Using multiple regression, greater perceived discrimination correlated with lower bilateral amygdala and anterior hippocampal volume, controlling for current stress, sex, education, age, and intracranial volume. Exploratory subfield analyses showed these associations were localized to the anterior hippocampal CA1 and subiculum. As predicted, using a moderation analysis, personal mastery attenuated the relationship between perceived discrimination and amygdala and anterior hippocampal volume. Here, we extend our knowledge on perceived discrimination as a salient psychosocial stressor with a neurobiological impact on brain systems implicated in stress, memory, and emotional regulation, and provide evidence for personal mastery as a moderating factor of these relationships.

Neurochemical Effects of Methylphenidate and Modafinil in Ameliorating Stress-Induced Cognitive Deficits

PURPOSE

Chronic stressful situations result in altered monoaminergic activity of neurotransmitters, resulting in various conditions characterized by deficits in learning, memory and attention. Stimulant effects can be visualized in terms of increased cognitive abilities through enhancement of dopamine (DA) release.

METHOD

This study examined cognitive responses and brain DA and 5-hydroxytryptamine (5HT) levels after prolonged methylphenidate (MPH) and modafinil administration, to demonstrate their effect on stress-induced cognitive deficits in rats. Effects on cognition were evaluated by passive avoidance and water maze tests. Furthermore brain levels of DA, homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), 5HT and 5-hydroxyindoleacetic acid (5HIAA) were analyzed by high-performance liquid chromatography coupled with electrochemical detection.

RESULTS

We found that both MPH and modafinil improved cognition in both restrained and unrestrained rats, as examined through water maze and passive avoidance tests. Furthermore, these substance were associated with increased brain DA and 5-HT levels. Notabily, we observed decrease in DOPAC and HVA levels, while 5-HIAA levels exhibited a slight increase.

CONCLUSIONS

The prevention of stress-induced cognitive deficits by MPH and modafinil could be elucidated through the interaction between 5HT and DA in regulating cognitive function.

The Molecular Relationship between Stress and Insomnia

The bi-directional relationship between sleep and stress has been actively researched as sleep disturbances and stress have become increasingly common in society. Interestingly, the brain and underlying neural circuits important for sleep regulation may respond uniquely to stress that leads to post-traumatic stress disorder (PTSD) and stress that does not. In stress that does not lead to PTSD, the hypothalamic-pituitary-adrenal axis (HPA) pathway is activated normally that results in sympathetic nervous system activation that allows the brain and body to return to baseline functioning. However, exposure to stress that leads to PTSD, causes enhanced negative feedback of this same pathway and results in long-term physiological and psychological changes. In this review, how stress regulates glucocorticoid signaling pathways in brain glial cells called astrocytes, and then mediates stress-induced insomnia are examined. Astrocytes are critical sleep regulatory cells and their connections to sleep and stress due to disturbed glucocorticoid signaling provide a novel mechanism to explain how stress leads to insomnia. This review will examine the interactions of stress neurobiology, astrocytes, sleep, and glucocorticoid signaling pathways and will examine the how stress that leads to PTSD and stress that does not impacts sleep-regulatory processes.

A literature review of the studies concerning selected plant-derived adaptogens and their general function in body with a focus on animal studies

BACKGROUND

Adaptogens are generally referred to the substances, mostly found in plants, which non-specifically increase resilience and chances of survival by activation of signaling pathways in affected cells.

PURPOSE

This literature review was conducted to summarize the investigation, until March 2021, on selected adaptogenic plants and plant-derived substances.

STUDY DESIGN

Electronic databases were searched (up to March 2021) for in vitro and animal studies, as well as clinical trials. Moreover, all modes of action connected with the adaptogenic effects of plants and phytochemicals were collected.

METHODS

The search of relevant studies was performed within electronic databases including Scopus, Science Direct, PubMed, and Cochrane library. The most important keywords were adaptogen, plant, phytochemical, and plant-derived.

RESULTS

The most investigated medicinal herbs for their adaptogenic activity are Eleutherococcus senticosus, Panax ginseng, Withania somnifera, Schisandra chinensis, and Rhodiola spp., salidroside, ginsenosides, andrographolide, methyl jasmonate, cucurbitacin R, dichotosin, and dichotosininare are phytochemicals that have shown a considerable adaptogenic activity. Phytochemicals that have been demonstrated adaptogenic properties mainly belong to flavonoids, terpenoids, and phenylpropanoid glycosides.

CONCLUSION

It is concluded that the main modes of action of the selected adaptogenic plants are stress modulatory, antioxidant, anti-fatigue, and physical endurance enhancement. Other properties were nootropic, immunomodulatory, cardiovascular, and radioprotective activities.

Resilience to chronic mild stress-induced anhedonia preserves the ability of the ventral hippocampus to respond to an acute challenge

Stress is a major precipitating factor for psychiatric disorders and its effects may depend on its duration and intensity. Of note, there are differences in individual susceptibility to stress, with some subjects displaying vulnerability and others showing resistance. Furthermore, the ability to react to stressful-life events can alter the response to a subsequent new stressor. Hence, we investigated whether the vulnerability and resilience to the chronic mild stress (CMS) paradigm, in terms of the hedonic phenotype, are paralleled by a different response when facing a novel acute challenge. Specifically, rats submitted to CMS were stratified based on their sucrose intake into vulnerable (anhedonic rats showing reduce intake of sucrose) and resilient (rats not showing the anhedonic-like behavior) subgroups and then further exposed to an acute restraint stress (ARS). Then, neuronal activation was investigated by measuring the gene expression of early immediate (IEG) genes such as Arc and Cfos and early response (ERG) genes, such as Gadd45β, Sgk1, Dusp1, and Nr4a1, in brain regions that play a crucial role in the stress response. We found that resilient rats preserve the ability to increase ERG expression following the ARS selectively in the ventral hippocampus. Conversely, such ability is lost in vulnerable rats. Interestingly, the recovery from the anhedonic phenotype observed in vulnerable rats after 3 weeks of rest from the CMS procedure also parallels the restoration of the ability to adequately respond to the challenge. In conclusion, these findings support the role of the ventral subregion of the hippocampus in the management of both chronic and acute stress response and point to this brain subregion as a critical target for a potential therapeutic strategy aimed at promoting stress resilience.

Corticotropin-releasing factor receptor 1 in infralimbic cortex modulates social stress-altered decision-making

Chronic stress could lead to a bias in behavioral strategies toward habits. However, it remains unclear which neuronal system modulates stress-induced behavioral abnormality during decision making. The corticotropin-releasing factor (CRF) system in the medial prefrontal cortex (mPFC), which has been implicated in governing strategy choice, is involved in the response to stress. The present study aimed to clarify whether altered function in cortical CRF receptors is linked to abnormal behaviors after chronic stress. In results, mice subjected to a 10-day social defeat preferred to use a habitual strategy. The infralimbic cortex (IL), but not the prelimbic cortex (PL) or anterior cingulate cortex (ACC), showed higher cFos expression in stress-subjected mice than in control mice, which may be associated with habitual behavior choice. Furthermore, CRF receptor 1 (CRFR1) agonist and antagonist infusion in IL during behavioral training mimicked and rescued stress-caused behavioral change in the decision-making assessment, respectively. An electrophysiological approach showed that the frequencies of both spontaneous IPSC and spontaneous EPSC, but not their amplitude, increased after stress and were modulated by CRFR1 agents. Further recordings revealed that an increased ratio of excitation to inhibition (E/I ratio) of IL by stress was rescued under conditions with CRFR1 antagonist. Collectively, these data indicate that CRFR1 plays a critical role in stress-permitted or enhanced glutamatergic and GABAergic presynaptic transmission in direct or indirect ways, as well as the modulation for E/I ratio in the IL. Thus, CRFR1 in the mPFC may be a proper target for treating cases of chronic stress-altered behavior.

Stress System Activation in Children and Adolescents With Autism Spectrum Disorder

The mission of the human stress system is the maintenance of homeostasis in the presence of real or perceived, acute or chronic stressors. The hypothalamic–pituitary–adrenal (HPA) axis and the autonomic nervous system (ANS) are the stress system-related neuroendocrine pathways. There is abundant evidence that children and adolescents with autism spectrum disorder (ASD) may exhibit atypical function within the HPA axis and the ANS both at the resting state and during the presence of social and/or non-social stressors. The aim of this review is to provide an up-to-date summary of the findings regarding stress system alterations in children and adolescents with ASD. We focus on the variations of stress hormones circadian rhythms, specifically cortisol and alpha-amylase (i.e., a surrogate index of epinephrine/norepinephrine secretion), and on the alterations of stress system responsivity to different stressors. Also, we present imaging and immunological findings that have been associated with stress system dysregulation in children and adolescents with ASD. Finally, we review the pivotal role of HPA axis-ANS coordination, the developmental trajectory of the stress system in ASD, and the possible role of early life stress in the dysregulation of the stress system demonstrated in children and adolescents with ASD. This synthesis will hopefully provide researchers with a foundation for an integrated approach to future research into stress system variations in children and adolescents with ASD.

Effects of Chronic Social Defeat Stress on Behavior and Dopamine Receptors in Adolescent Mice With 6-Hydroxydopamine Lesions of the Medial Prefrontal Cortex

Background: Social stress factors in schizophrenia have long-term effects, but will only induce symptoms in a portion of individuals, even if exposed to identical stress.

Methods: In the current experiment, we examined mice with 6-hydroxydopamine (6-OHDA)-induced medial prefrontal cortical (mPFC) injury to select for members of a “stress-susceptible group,” and observed the changes in their behavior and the expression of D1 and D2 dopamine receptors in the amygdala and hippocampus.

Results: We observed that after chronic social defeat stress, 72.6% of the 6-OHDA lesioned mice exhibited stress response to aggressors, compared to 52.3% of the blank control group. Both the 6-OHDA lesion + social defeat and social defeat groups exhibited anxiety and depression-like behavior. However, social cognitive impairment in the mice from the 6-OHDA lesion + social defeat group was more significant and the D1 expression levels in the amygdala were significantly decreased.

Conclusion: These results suggest that the reason that adolescent mice with cortical injury were highly sensitive to defeat stress and had more prominent social cognitive impairment may be the decreased selectivity of D1 in the amygdala.

Perinatal Complications as a Mediator of the Association Between Chronic Disease and Postpartum Mental Illness

Background: Chronic disease is associated with increased risk of postpartum mental illness, but the mechanisms underlying this association are unclear. Our aim was to explore the mediating role of perinatal complications in the association between chronic disease and postpartum mental illness. Materials and Methods: This was a population-based retrospective cohort study of all women in Ontario, Canada, from 2005 to 2015 with a singleton live birth and no recent history of mental illness during or 2 years before pregnancy. The outcome was mental illness diagnosis between delivery and 365 days postpartum, with perinatal complications, including pregnancy, delivery, and neonatal complications. Modified Poisson regression models were used to examine the association between chronic disease and perinatal mental illness, with generalized estimating equations for the calculation of total, direct, and indirect effects. All models were adjusted for sociodemographic characteristics and remote history of mental health care. Results: Of the 792,972 women, 21.1% had a chronic disease. Chronic disease was associated with an increased risk of postpartum mental illness (adjusted relative risk [aRR] 1.15 [95% confidence interval, CI 1.14-1.16]). There was no evidence of an indirect effect of chronic disease on postpartum mental illness via perinatal complications (aRR 1.003, 95% CI 1.002-1.003). Perinatal complications explained only 1.5% of the association between chronic disease and postpartum mental illness. Results were consistent by type of perinatal complication and chronic disease diagnosis. Conclusion: We observed no clinically meaningful mediating effect of perinatal complications in the association between chronic disease and postpartum mental illness. Future research should investigate alternative mechanisms explaining this association.

Connectome-Based Predictive Modeling of Individual Anxiety

Anxiety-related illnesses are highly prevalent in human society. Being able to identify neurobiological markers signaling high trait anxiety could aid the assessment of individuals with high risk for mental illness. Here, we applied connectome-based predictive modeling (CPM) to whole-brain resting-state functional connectivity (rsFC) data to predict the degree of trait anxiety in 76 healthy participants. Using a computational “lesion” approach in CPM, we then examined the weights of the identified main brain areas as well as their connectivity. Results showed that the CPM successfully predicted individual anxiety based on whole-brain rsFC, especially the rsFC between limbic areas and prefrontal cortex. The prediction power of the model significantly decreased from simulated lesions of limbic areas, lesions of the connectivity within limbic areas, and lesions of the connectivity between limbic areas and prefrontal cortex. Importantly, this neural model generalized to an independent large sample (n = 501). These findings highlight important roles of the limbic system and prefrontal cortex in anxiety prediction. Our work provides evidence for the usefulness of connectome-based modeling in predicting individual personality differences and indicates its potential for identifying personality factors at risk for psychopathology.

Noli Timere: The Role of Reassuring Adults in Dealing with COVID-19 Anxiety in Pediatric Age

Since the earliest stages of the Corona Virus Disease-19 (COVID-19) spread, the elderly has been identified as the most vulnerable and health authorities have rightly focused on that population. Minor attention was paid to pediatric populations and their emotional reactions. Actually, children and adolescents faced severe anxiety, fear and stress conditions. An efficient management of the pandemic, therefore, must take into account the pediatric population which cannot be neglected as a minor matter compared to the elderly, the economy and health care. Since the lockdown time is over, children and adolescents must recover sociality, return to living in the open air, rediscover playing, free time, aiming for the beauty of their everyday life. In order to mitigate the long-term impact of COVID-19, the key response is the reassuring presence of the adult as 'a secure base'. The current study aimed to collect an overview of the recent references that report evidence on the role of adults in containing pandemic anxiety COVID-19 in pediatric populations, suggesting the need to ensure a reassuring presence of the adult, an effective child-parent communication, a child-friendly day and a long-lasting shared time with parents.

Brain circuits at risk in psychiatric diseases and pharmacological pathways

The multiple brain circuits involved in psychiatric diseases may appear daunting, but we prefer to concentrate on a select few, with a particular sensitivity to stress and neurodevelopmental issues, with a clear pharmacotherapy. This review is structured around 1. the key circuits, their role in health and disease, and the neurotransmitters maintaining them, 2. The influence of upbringing, stress, chronobiology, inflammation and infection, 3. The genetic and epigenetic influence on these circuits, particularly regarding copy number variants and neuronal plasticity, 4. The use and abuse of pharmacological agents with the particular risks of stress and chronobiology at critical periods. A major emphasis is placed on the links between hippocampus, prefrontal cortex and amygdala/periaqueductal grey which control specific aspects of cognition, mood, pain and even violence. Some of the research findings were from the innovative medicine initiative (IMI) NEWMEDS, a 22M€ academic/industrial consortium on the brain circuits critical for psychiatric disease.

Differential sensitivity to the acute psychotomimetic effects of delta-9-tetrahydrocannabinol associated with its differential acute effects on glial function and cortisol

BACKGROUND

Cannabis use has been associated with psychosis through exposure to delta-9-tetrahydrocannabinol (Δ9-THC), its key psychoactive ingredient. Although preclinical and human evidence suggests that Δ9-THC acutely modulates glial function and hypothalamic-pituitary-adrenal (HPA) axis activity, whether differential sensitivity to the acute psychotomimetic effects of Δ9-THC is associated with differential effects of Δ9-THC on glial function and HPA-axis response has never been tested.

METHODS

A double-blind, randomized, placebo-controlled, crossover study investigated whether sensitivity to the psychotomimetic effects of Δ9-THC moderates the acute effects of a single Δ9-THC dose (1.19 mg/2 ml) on myo-inositol levels, a surrogate marker of glia, in the Anterior Cingulate Cortex (ACC), and circadian cortisol levels, the key neuroendocrine marker of the HPA-axis, in a set of 16 healthy participants (seven males) with modest previous cannabis exposure.

RESULTS

The Δ9-THC-induced change in ACC myo-inositol levels differed significantly between those sensitive to (Δ9-THC minus placebo; M = -0.251, s.d. = 1.242) and those not sensitive (M = 1.615, s.d. = 1.753) to the psychotomimetic effects of the drug (t(14) = 2.459, p = 0.028). Further, the Δ9-THC-induced change in cortisol levels over the study period (baseline minus 2.5 h post-drug injection) differed significantly between those sensitive to (Δ9-THC minus placebo; M = -275.4, s.d. = 207.519) and those not sensitive (M = 74.2, s.d. = 209.281) to the psychotomimetic effects of the drug (t(13) = 3.068, p = 0.009). Specifically, Δ9-THC exposure lowered ACC myo-inositol levels and disrupted the physiological diurnal cortisol decrease only in those subjects developing transient psychosis-like symptoms.

CONCLUSIONS

The interindividual differences in transient psychosis-like effects of Δ9-THC are the result of its differential impact on glial function and stress response.

Anxiety in Older Adolescents at the Time of COVID-19

Corona Virus Disease-19 (COVID-19) is a catastrophic health risk, with psychological, emotional, social, and relational implications. From the early stages of the virus spread, the elderly population was identified as the most vulnerable, and health authorities have rightly focused on this frailer population. Conversely, less attention was given to the emotional and psychological dimensions of children and adolescents. Moreover, even though they were the subjects whose lives and health were at low risk, they, nevertheless, had to face a reality full of anxiety, fears, and uncertainties. The current study investigated the state of anxiety and emotional awareness in a sample of healthy older adolescents, 84 females and 64 males, aged 17 to 19, during the pandemic lockdown, using the Self-Rating Anxiety Scale and the Italian Emotion Awareness Questionnaire. An unexpected anxious phenomenology was found, affecting anxiety and the ideo-affective domain, while somatic symptomatology appeared to be less severe. The highest anxiety symptoms were breathing difficulties. These findings supported the hypothesis that the COVID-19 pandemic may be a risk condition for an increased state of anxiety in older adolescents and suggested the need to provide (1) an effective, empathic communication system with direct participation of older adolescents, (2) a psychological counseling service for the stress management of adolescents.

Memory performances and personality traits in mothers of children with obstructive sleep apnea syndrome

Background

Chronic diseases in pediatric age have been identified as stressful risk factors for parents. Studies on caregivers have documented the impact of chronic parenting stress on emotion and cognition.

Aim

To investigate the differences between a group of mothers of children affected by obstructive sleep apnea syndrome (OSAS) for at least 4 years and a group of mothers of typically developing children (TDC) in relation to parental stress, self-esteem, locus of control, and memory performances.

Methods

A group of 86 mothers (mean age 35.6±4.9, ranged between 32 and 41 years) of children with OSAS diagnosis, and a group of 52 mothers of TDC (mean age 35.9±4.2, ranged between 32 and 41 years) participated in the study. All participants were administered stress level, global self-esteem, internal/external locus of control scales, and memory assessment.

Results

Mothers of OSAS children, compared to mothers of TDC, had a significantly higher level of stress, lower self-esteem, more external locus of control and poorer memory performance.

Conclusions

The child respiratory disease, with its sudden and unpredictable features, appeared as a significant source of stress for the mother. Such stress condition may have an impact on mothers’ personality traits (self-esteem, locus of control) and on their memory performances. The data have suggested a need for psychological support programs for mothers to better manage stress associated with children’s respiratory disease.

Disrupted compensatory response mediated by Wolfram syndrome 1 protein and corticotrophin-releasing hormone family peptides in early-onset intrahepatic cholestasis pregnancy

INTRODUCTION

The most adverse perinatal outcome of intrahepatic cholestasis of pregnancy (ICP) is sudden fetal death related to acute fetoplacental hypoxia. Corticotrophin-releasing hormone (CRH), urocortin (UCN), and Wolfram syndrome 1 (WFS1) proteins may have a compensatory response to hypoxic stress.

METHODS

A total of 108 singleton pregnant women were divided into three groups: control, late-onset ICP, and early-onset ICP. Enzyme-linked immunosorbent assays were used to detected maternal serum CRH, UCN, and WFS1 levels. Western blotting and real-time polymerase chain reaction were conducted to quantify placental protein and mRNA levels of CRH, UCN, and WFS1. Pearson correlation scatterplots and Pearson correlation matrix were employed to testify the correlation.

RESULTS

Placental WFS1 had a positive relation with placental UCN (r = 0.69, P < 0.05) and serum UCN (r = 0.36, P < 0.05). Placental CRH was positively correlated with maternal serum CRH (r = 0.53, P < 0.05). Maternal serum and placental levels of CRH, UCN, and WFS1 significantly increased in the early-onset ICP group compared with the control group (P < 0.05). Placental levels of UCN and WFS1 in the early-onset ICP group were significantly elevated and higher in comparison with the late-onset ICP group (P < 0.05). However, the transcriptional levels of CRH, UCN, and WFS1 were impaired in the early-onset ICP group.

DISCUSSION

Our study revealed that transcription and translation of WFS1, CRH, and UCN were altered during pregnancies complicated by early-onset ICP. This disrupted compensatory response mediated by WFS1 and CRH family peptides in early-onset ICP may play a significant role in the pathogenesis of sudden fetal death in acute fetal hypoxia.

Hair Cortisol Measurement by an Automated Method

We present the development of the first procedure for hair cortisol measurement through an automated method. Hair samples were obtained from 286 individuals. After cortisol extraction, samples were measured in a Siemens Immulite 2000 (Gwynedd, UK) automated chemoluminiscent immunoassay analyzer. Normal reference values were obtained from hair cortisol levels measured in 213 healthy individuals with low levels of stress. Hair cortisol concentration median was 55 pg/mg hair (2.5–97.5 percentile (40–128)) in healthy individuals with low levels of stress and 250 pg/mg hair (range 182–520) in stressed individuals. No significant differences were observed in hair cortisol levels between subjects with and without dye (40 (40–107) and 40 (40–155) pg/mg hair, respectively; p = 0.128). The novel procedure presented here shows an adequate analytical performance.

Risk of benign paroxysmal positional vertigo in patients with depressive disorders: a nationwide population-based cohort study

OBJECTIVE

The association between depression and benign paroxysmal positional vertigo (BPPV) remains debated. This study aimed to investigate the risk of BPPV in patients with depressive disorders.

DESIGN

Longitudinal nationwide cohort study.

SETTING

National health insurance research database in Taiwan.

PARTICIPANTS

We enrolled 10 297 patients diagnosed with depressive disorders between 2000 and 2009 and compared them to 41 188 selected control patients who had never been diagnosed with depressive disorders (at a 1:4 ratio matched by age, sex and index date) in relation to the risk of developing BPPV.

METHODS

The follow-up period was defined as the time from the initial diagnosis of depressive disorders to the date of BPPV, censoring or 31 December 2009. Cox proportional hazard regression analysis was used to investigate the risk of BPPV by sex, age and comorbidities, with HRs and 95% CIs.

RESULTS

During the 9-year follow-up period, 44 (0.59 per 1000 person-years) patients with depressive disorders and 99 (0.33 per 1000 person-years) control patients were diagnosed with BPPV. The incidence rate ratio of BPPV among both cohorts calculating from events of BPPV per 1000 person-years of observation time was 1.79 (95% CI 1.23 to 2.58, p=0.002). Following adjustments for age, sex and comorbidities, patients with depressive disorders were 1.55 times more likely to develop BPPV (95% CI 1.08 to 2.23, p=0.019) as compared with control patients. In addition, hyperthyroidism (HR=3.75, 95% CI 1.67-8.42, p=0.001) and systemic lupus erythematosus (SLE) (HR=3.47, 95% CI 1.07 to 11.22, p=0.038) were potential risk factors for developing BPPV in patients with depressive disorders.

CONCLUSIONS

Patients with depressive disorders may have an increased risk of developing BPPV, especially those who have hyperthyroidism and SLE.

The orbitofrontal cortex modulates parenting stress in the maternal brain

Many mothers are adaptive, deploying successful coping strategies that mitigate the deleterious effects of parenting stress on caregiving, nevertheless, the neural mechanisms underlying these adaptive responses remain unclear. We utilized functional magnetic resonance imaging to investigate brain activity in 28 healthy mothers of typically developing, 2-to-3-year-old children in response to the feeding behavior of their own children versus that of other children. We then examined the correlation between maternal brain activation and subjective feelings of parenting stress. Brain regions associated with maternal motivation including the orbitofrontal cortex (OFC), ventral pallidum, periaqueductal gray (PAG), dorsal raphe nucleus (DRN), and anterior insular cortex (AIC)—as well as those associated with the recognition of one’s own child’s state (e.g., cerebellum)—exhibited significant activation in response to their own children. While mothers with higher activation in the OFC showed less parenting stress related to one’s sense of competence in the parental role, mothers with higher co-activation of the OFC with both of the AIC and PAG/DRN, and with the cerebellum showed less parenting stress caused by child characteristics. Our findings suggest that well-balanced maternal brain mechanisms integrated by the OFC may provide effective adaptive responses in daily parenting scenarios.

Effects of glucocorticoids in depression: Role of astrocytes

Astrocytes or astroglia are heterogeneous cells, similar to neurons, that have different properties in different brain regions. The implications of steroid hormones on glial cells and stress-related pathologies have been studied previously. Glucocorticoids (GCs) that are released in response to stress have been shown to be deleterious to neurons in various brain regions. Further, in the light of the effect of GCs on astrocytes, several reports have shown the crucial role of glia. Still, much remains to be done to understand the stress-astrocytes-glucocorticoid interactions associated with the pathological consequences of various CNS disorders. This review is an attempt to summarize the effects of GCs and stress on astrocytes and its implications in depression.

Psychosocial Factors and Sport Injuries: Meta-analyses for Prediction and Prevention

BACKGROUND

Several studies have suggested that psychosocial variables can increase the risk of becoming injured during sport participation.

OBJECTIVES

The main objectives of these meta-analyses were to examine (i) the effect sizes of relationships between the psychosocial variables (suggested as injury predictors in the model of stress and athletic injury) and injury rates, and (ii) the effects of psychological interventions aimed at reducing injury occurrence (prevention).

METHODS

Electronic databases as well as specific sport and exercise psychology journals were searched. The literature review resulted in 48 published studies containing 161 effect sizes for injury prediction and seven effect sizes for injury prevention.

RESULTS

The results showed that stress responses (r = 0.27, 80 % CI [0.20, 0.33]) and history of stressors (r = 0.13, 80 % CI [0.11, 0.15]) had the strongest associations with injury rates. Also, the results from the path analysis showed that the stress response mediated the relationship between history of stressors and injury rates. For injury prevention studies, all studies included (N = 7) showed decreased injury rates in the treatment groups compared to control groups.

CONCLUSION

The results support the model's suggestion that psychosocial variables, as well as psychologically, based interventions, can influence injury risk among athletes.

Limbic brain structures and burnout-A systematic review

More profound understanding of the relationship between the burnout and the limbic system function can provide better insight into brain structures associated with the burnout syndrome. The objective of this review is to explore all evidence of limbic brain structures associated with the burnout syndrome. In total, 13 studies were selected. Four of them applied the neuroimaging technology to investigate the sizes/volumes of the limbic brain structures of burnout patients. Six other studies were to investigate the hypothalamus-pituitary-adrenal (HPA) axis of burnout patients. Based on the results of the studies on the HPA-axis and neuroimaging of the limbic brain structures, one can see great impact of the chronic occupational stress on the limbic structures in terms of HPA dysregulation, a decrease of BDNF, impaired neurogenesis and limbic structures atrophy. It can be concluded that chronic stress inhibits the feedback control pathway in the HPA axis, causes the decrease of brain-derived neurotrophic factor (BDNF), then impaired neurogenesis and eventually neuron atrophy.

Receptor-driven, multimodal mapping of the human amygdala

The human amygdala consists of subdivisions contributing to various functions. However, principles of structural organization at the cellular and molecular level are not well understood. Thus, we re-analyzed the cytoarchitecture of the amygdala and generated cytoarchitectonic probabilistic maps of ten subdivisions in stereotaxic space based on novel workflows and mapping tools. This parcellation was then used as a basis for analyzing the receptor expression for 15 receptor types. Receptor fingerprints, i.e., the characteristic balance between densities of all receptor types, were generated in each subdivision to comprehensively visualize differences and similarities in receptor architecture between the subdivisions. Fingerprints of the central and medial nuclei and the anterior amygdaloid area were highly similar. Fingerprints of the lateral, basolateral and basomedial nuclei were also similar to each other, while those of the remaining nuclei were distinct in shape. Similarities were further investigated by a hierarchical cluster analysis: a two-cluster solution subdivided the phylogenetically older part (central, medial nuclei, anterior amygdaloid area) from the remaining parts of the amygdala. A more fine-grained three-cluster solution replicated our previous parcellation including a laterobasal, superficial and centromedial group. Furthermore, it helped to better characterize the paralaminar nucleus with a molecular organization in-between the laterobasal and the superficial group. The multimodal cyto- and receptor-architectonic analysis of the human amygdala provides new insights into its microstructural organization, intersubject variability, localization in stereotaxic space and principles of receptor-based neurochemical differences.

Social evaluative threat with verbal performance feedback alters neuroendocrine response to stress

Laboratory stress tasks such as the Trier Social Stress Test (TSST) have provided a key piece to the puzzle for how psychosocial stress impacts the hypothalamic-pituitary-adrenal axis, other stress-responsive biomarkers, and ultimately wellbeing. These tasks are thought to work through biopsychosocial processes, specifically social evaluative threat and the uncontrollability heighten situational demands. The present study integrated an experimental modification to the design of the TSST to probe whether additional social evaluative threat, via negative verbal feedback about speech performance, can further alter stress reactivity in 63 men and women. This TSST study confirmed previous findings related to stress reactivity and stress recovery but extended this literature in several ways. First, we showed that additional social evaluative threat components, mid-task following the speech portion of the TSST, were still capable of enhancing the psychosocial stressor. Second, we considered stress-reactive hormones beyond cortisol to include dehydroepiandrosterone (DHEA) and testosterone, and found these hormones were also stress-responsive, and their release was coupled with one another. Third, we explored whether gain- and loss-framing incentive instructions, meant to influence performance motivation by enhancing the personal relevance of task performance, impacted hormonal reactivity. Results showed that each hormone was stress reactive and further had different responses to the modified TSST compared to the original TSST. Beyond the utility of showing how the TSST can be modified with heightened social evaluative threat and incentive-framing instructions, this study informs about how these three stress-responsive hormones have differential responses to the demands of a challenge and a stressor.

Role of Elsholtzia communis in counteracting stress by modulating expression of hspa14, C/EBP homologous protein, nuclear factor (erythroid-derived 2)-like-2 factor, Caspase-3, and brain-derived neurotrophic factor in rat hippocampus

OBJECTIVE:

Elsholtzia communis (Collett and Hemsl.) Diels has been widely distributed and is reported for many therapeutic effects. The present study aims to investigate the antistress activity of the leaf extract and its possible molecular mechanism.

MATERIALS AND METHODS:

Hydroethanolic extract of leaves of E. communis (100 and 200 mg/kg, p.o.) were administered for 7 days to stress-induced male Wistar rats. The experimental animals were divided into five groups (n = 6). The mRNA/protein profile of few stress responsive chaperones (hspa14), endoplasmic reticulum stress markers (C/EBP homologous protein [CHOP]), antioxidant regulating genes (nuclear factor (erythroid-derived 2)-like-2 factor [Nrf2]), apoptotic factors (Caspase-3) in rat hippocampus were studied by polymerase chain reaction and immunoblotting.

RESULTS:

The stress-related genes such as hspa14, CHOP, antioxidant gene Nrf2, apoptotic gene Caspase-3 which were overexpressed in the stress control group were significantly suppressed following administration of the extract at both the doses and the standard drug Ginseng. Likewise, brain-derived neurotrophic factor which is closely related with stress, was downregulated in the stress control group, was found to be upregulated following treatment with the extract and the standard drug Ginseng.

CONCLUSION:

Our findings clearly indicate that E. communis was able to counteract stress. Hence, it has the potential to develop as adaptogen and also as a replacement/substitute of the popularly used drug, Ginseng or Ashwagandha, which is on the verge of extinction or becoming endemic due to overuse.

Examining Brain Morphometry Associated with Self-Esteem in Young Adults Using Multilevel-ROI-Features-Based Classification Method

Purpose: This study is to exam self-esteem related brain morphometry on brain magnetic resonance (MR) images using multilevel-features-based classification method.

Method: The multilevel region of interest (ROI) features consist of two types of features: (i) ROI features, which include gray matter volume, white matter volume, cerebrospinal fluid volume, cortical thickness, and cortical surface area, and (ii) similarity features, which are based on similarity calculation of cortical thickness between ROIs. For each feature type, a hybrid feature selection method, comprising of filter-based and wrapper-based algorithms, is used to select the most discriminating features. ROI features and similarity features are integrated by using multi-kernel support vector machines (SVMs) with appropriate weighting factor.

Results: The classification performance is improved by using multilevel ROI features with an accuracy of 96.66%, a specificity of 96.62%, and a sensitivity of 95.67%. The most discriminating ROI features that are related to self-esteem spread over occipital lobe, frontal lobe, parietal lobe, limbic lobe, temporal lobe, and central region, mainly involving white matter and cortical thickness. The most discriminating similarity features are distributed in both the right and left hemisphere, including frontal lobe, occipital lobe, limbic lobe, parietal lobe, and central region, which conveys information of structural connections between different brain regions.

Conclusion: By using ROI features and similarity features to exam self-esteem related brain morphometry, this paper provides a pilot evidence that self-esteem is linked to specific ROIs and structural connections between different brain regions.

Alterations in VEGF expression induced by antidepressant drugs in female rats under chronic social stress

Vascular endothelial growth factor (VEGF) is thought to serve a role in neurogenesis and the stress response. Although a definite link between the action of antidepressants and VEGF has not been identified, it is assumed that VEGF, as a neurotrophic factor, serves an important role in the effects of antidepressant treatment. To examine this, the present study subjected adult female rats to four weeks of social instability stress and measured the effect of antidepressant treatment on the expression of VEGF. Firstly, endocrine markers of stress and body weight were measured in parallel with behavioral tests prior to and following subjection to stress. Then, the effect of 28-day daily treatment with desipramine (DMI; 10 mg/kg), fluoxetine (5 mg/kg) or tianeptine (10 mg/kg) on the number of copies of VEGF mRNA in the amygdala, hippocampus and hypothalamus, and on serum VEGF protein levels, of rats subjected to chronic stress was determined. In addition, the weight of the adrenal glands was measured following subjection to stress. Exposure to chronic stress was found to increase the rats' sucrose preference, and diminish their tendency for general exploration and time spent in the open. The relative adrenal weights of the stressed rats were significantly increased compared with the control. Plasma concentrations of corticosterone and adrenocorticotropic hormone were not significantly augmented. In addition, the present study identified that stress elevated VEGF mRNA expression in all studied neural structures. Furthermore, the results identified that the stress-induced increase in VEGF mRNA expression in the amygdala and hypothalamus was attenuated by long-term administration of DMI. Conversely, a decrease in serum VEGF concentration was observed in stressed rats, which was not reversed by treatment with antidepressants. In conclusion, the current study suggests that under conditions of stress, VEGF serves a role in the mechanism of action of DMI, through modulating activity of the norepinephrine system.

Synaptic Plasticity, Metaplasticity and Depression

The development of a persistent depressive affective state has for some time been thought to result from persistent alterations in neurotransmitter-mediated synaptic transmission. While the identity of those transmitters has changed over the years, the literature has lacked mechanistic connections between the neurophysiological mechanisms they regulate, and how these mechanisms alter neuronal function, and, hence, affective homeostasis. This review will examine recent work that suggests that both long-term activity-dependent changes in synaptic strength (“plasticity”), and shifting set points for the ease of induction of future long-term changes (“metaplasticity”), may be critical to establishing and reversing a depressive behavioral state. Activity-dependent long-term synaptic plasticity involves both strengthening and weakening of synaptic connections associated with a dizzying array of neurochemical alterations that include synaptic insertion and removal of a number of subtypes of AMPA, NMDA and metabotropic glutamate receptors, changes in presynaptic glutamate release, and structural changes in dendritic spines. Cellular mechanisms of metaplasticity are far less well understood. Here, we will review the growing evidence that long-term synaptic changes in glutamatergic transmission, in brain regions that regulate mood, are key determinants of affective homeostasis and therapeutic targets with immense potential for drug development.

Effects of acute and chronic stress on telencephalic neurochemistry and gene expression in rainbow trout (Oncorhynchus mykiss)

By filtering relevant sensory inputs and initiating stress responses, the brain is an essential organ in stress coping and adaptation. However, exposure to chronic or repeated stress can lead to allostatic overload, where neuroendocrinal and behavioral reactions to stress become maladaptive. This work examines forebrain mechanisms involved in allostatic processes in teleost fishes. Plasma cortisol, forebrain serotonergic (5-HTergic) neurochemistry, and mRNA levels of corticotropin-releasing factor (CRF), CRF-binding protein (CRF-BP), CRF receptors (CRFR1 and CRFR2), mineralocorticoid receptor (MR), glucocorticoid receptors (GR1 and GR2) and serotonin type 1A (5-HT_1A) receptors (5-HT_1Aα and 5-HT_1Aβ) were investigated at 1 h before and 0, 1 and 4 h after acute stress, in two groups of rainbow trout held in densities of 25 and 140 kg m^-3 for 28 days. Generally, being held at 140 kg m^-3 resulted in a less pronounced cortisol response. This effect was also reflected in lower forebrain 5-HTergic turnover, but not in mRNA levels in any of the investigated genes. This lends further support to reports that allostatic load causes fish to be incapable of mounting a proper cortisol response to an acute stressor, and suggests that changes in forebrain 5-HT metabolism are involved in allostatic processes in fish. Independent of rearing densities, mRNA levels of 5-HT_1Aα and MR were downregulated 4 h post-stress compared with values 1 h post-stress, suggesting that these receptors are under feedback control and take part in the downregulation of the hypothalamic-pituitary-interrenal (HPI) axis after exposure to an acute stressor.

Association between major depressive disorder and odor identification impairment

BACKGROUND

There is evidence of olfactory deficits in patients with major depressive disorder (MDD) but causes and mechanisms are largely unknown.

METHODS

We compared 728 patients with current MDD and 555 non-depressed controls regarding odor identification impairment taking into account the severity of acute symptoms and of the disease course. We assessed current symptom severity with the Hamilton Depression Rating Scale, and disease course severity based on admission diagnosis (ICD-10, F32/F33) and self-reported hospitalization frequency, defined as infrequent (<2) and frequent (≥2) depression-related hospitalizations under constant disease duration. A score of <10 on the Sniffin' Sticks-Screen-12 test determined the presence of odor identification impairment.

RESULTS

Compared to non-depressed controls patients with frequent (rapidly recurring) hospitalizations had an elevated chance of odor identification impairment, even after adjustment for smell-influencing factors, such as age and smoking, (OR=1.7; 95% CI 1.0-2.9). Patients with recurrent MDD (F33) also had an elevated odds of odor identification impairment compared to those with a first-time episode (F32, OR=1.5; 95% CI 1.0-2.4). In patients with a first-time episode the chance of odor identification impairment increased by 7% with each point increase in the Hamilton Score.

LIMITATIONS

Cross-sectional study. Variation in the use of psychotropic medication is a potential bias.

CONCLUSION

Odor identification impairment was evident in MDD patients with first-time high symptom severity and in patients with a severe disease course. Whether odor identification impairment is a marker or mediator of structural and functional brain changes associated with acute or active MDD requires further investigations in longitudinal studies.

Whole-brain mapping of afferent projections to the bed nucleus of the stria terminalis in tree shrews

The bed nucleus of the stria terminalis (BST) plays an important role in integrating and relaying input information to other brain regions in response to stress. The cytoarchitecture of the BST in tree shrews (Tupaia belangeri chinensis) has been comprehensively described in our previous publications. However, the inputs to the BST have not been described in previous reports. The aim of the present study was to investigate the sources of afferent projections to the BST throughout the brain of tree shrews using the retrograde tracer Fluoro-Gold (FG). The present results provide the first detailed whole-brain mapping of BST-projecting neurons in the tree shrew brain. The BST was densely innervated by the prefrontal cortex, entorhinal cortex, ventral subiculum, amygdala, ventral tegmental area, and parabrachial nucleus. Moreover, moderate projections to the BST originated from the medial preoptic area, supramammillary nucleus, paraventricular thalamic nucleus, pedunculopontine tegmental nucleus, dorsal raphe nucleus, locus coeruleus, and nucleus of the solitary tract. Afferent projections to the BST are identified in the ventral pallidum, nucleus of the diagonal band, ventral posteromedial thalamic nucleus, posterior complex of the thalamus, interfascicular nucleus, retrorubral field, rhabdoid nucleus, intermediate reticular nucleus, and parvicellular reticular nucleus. In addition, the different densities of BST-projecting neurons in various regions were analyzed in the tree shrew brains. In summary, whole-brain mapping of direct inputs to the BST is delineated in tree shrews. These brain circuits are implicated in the regulation of numerous physiological and behavioral processes including stress, reward, food intake, and arousal.

Increased risk of benign paroxysmal positional vertigo in patients with anxiety disorders: a nationwide population-based retrospective cohort study

BACKGROUND

The objective of this study was to evaluate the risk of benign peripheral persistent vertigo (BPPV) among patients with anxiety disorders by using the Taiwan National Health Insurance Research Database (NHIRD).

METHODS

We conducted a retrospective study of 15,470 participants (7735 anxiety disorder patients and 7735 control patients) selected from the NHIRD. Patients were observed for a maximum of 9 years to determine the rates of newly diagnosed BPPV. A Cox regression model was used to evaluate the risk of BPPV among the patients with anxiety disorders.

RESULTS

During the 9-year follow-up period, 178 (2.05 per 1000 person-years) anxiety disorder patients and 71 (0.81 per 1000 person-years) control patients were diagnosed with BPPV. The incidence risk ratio of BPPV between anxiety disorder patients and control patients was 2.52 (95 % confidence interval [CI], 1.90-3.37, P < .001). After adjustment for age, sex, and comorbidities, patients with anxiety disorders were found to be 2.17 times more likely to develop BPPV (95 % CI, 1.63-2.90, P < .001) than the control patients. Furthermore, female sex (HR = 1.81, 95 % CI, 1.31-2.50, P < .001) and cerebrovascular disease (HR = 1.53, 95 % CI, 1.00-2.34, P = .050) were independent risk factors for developing new-onset BPPV in patients with anxiety disorders.

CONCLUSIONS

Anxiety disorder patients may have an increased risk of developing BPPV, especially those who are female or have cerebrovascular disease.

Role of Glia in Stress-Induced Enhancement and Impairment of Memory

Both acute and chronic stress profoundly affect hippocampally-dependent learning and memory: moderate stress generally enhances, while chronic or extreme stress can impair, neural and cognitive processes. Within the brain, stress elevates both norepinephrine and glucocorticoids, and both affect several genomic and signaling cascades responsible for modulating memory strength. Memories formed at times of stress can be extremely strong, yet stress can also impair memory to the point of amnesia. Often overlooked in consideration of the impact of stress on cognitive processes, and specifically memory, is the important contribution of glia as a target for stress-induced changes. Astrocytes, microglia, and oligodendrocytes all have unique contributions to learning and memory. Furthermore, these three types of glia express receptors for both norepinephrine and glucocorticoids and are hence immediate targets of stress hormone actions. It is becoming increasingly clear that inflammatory cytokines and immunomodulatory molecules released by glia during stress may promote many of the behavioral effects of acute and chronic stress. In this review, the role of traditional genomic and rapid hormonal mechanisms working in concert with glia to affect stress-induced learning and memory will be emphasized.

Hypothalamic-pituitary-adrenal (HPA) axis and aging

Human aging is associated with increasing frailty and morbidity which can result in significant disability. Dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis may contribute to aging-related diseases like depression, cognitive deficits, and Alzheimer's disease in some older individuals. In addition to neuro-cognitive dysfunction, it has also been associated with declining physical performance possibly due to sarcopenia. This article reviews the pathophysiology of HPA dysfunction with respect to increased basal adrenocorticotropic hormone (ACTH) and cortisol secretion, decreased glucocorticoid (GC) negative feedback at the level of the paraventricular nucleus (PVN) of the hypothalamus, hippocampus (HC), and prefrontal cortex (PFC), and flattening of diurnal pattern of cortisol release. It is possible that the increased cortisol secretion is secondary to peripheral conversion from cortisone. There is a decline in pregnolone secretion and C-19 steroids (DHEA) with aging. There is a small decrease in aldosterone with aging, but a subset of the older population have a genetic predisposition to develop hyperaldosteronism due to the increased ACTH stimulation. The understanding of the HPA axis and aging remains a complex area with conflicting studies leading to controversial interpretations.

Effect of cake-separated moxibustion on expression of mineralocorticoid receptor, glucocorticoid receptor and 5-hydroxytryptamine receptor 1A in the hippocampus of functional dyspepsia rats with liver-stagnation and spleen-deficiency syndrome

AIM: To observe the effect of cake-separated moxibustion on the expression of mineralocorticoid receptor (MR), glucocorticoid receptor (GR) and 5-hydroxytryptamine receptor 1A (5-HTR1A) in the hippocampus of rats with functional dyspepsia (FD), and to explore the possible mechanism underlying the therapeutic effect of cake-separated moxibustion on FD.

METHODS: Fifty SD rats were randomly divided into five groups: a blank group (A), a model group (B), a cake-separated moxibustion group (C), a Xiaoyaosan group (D) and a domperidone group (E), with 10 rats in each group. Except group A, the other four groups received chronic restraint stress + excessive fatigue + irregular food for 3 wk. After molding, group C received herbal cake-separated moxibustion for 2 wk, and groups D and E were given Xiaoyaosan and domperidone by gavage for the same duration, respectively. At the end of the experiment, gastric emptying was observed and the expression of MR, GR and 5-HTR1A in the hippocampus was measured by real-time fluorescence quantitative PCR (RT-PCT).

RESULTS: The rate of gastric emptying in model rats was significantly lower than that of group A (P < 0.01), while the rates of gastric emptying in the three treatment groups were significantly higher than that in group B (P < 0.01 for all), although there were no significant differences among the three treatment groups (P > 0.05). The expression of MR in the hippocampus in group B was statistically alike to that in group A (P > 0.05), while the expression of GR and 5-HTR1A was significantly lower than that in group A (P < 0.05 for both). Compared with group B, the expression of MR in the hippocampus in groups C, D and E was statistically similar (P > 0.05), but the expression of GR and 5-HTR1A was significantly higher (P < 0.05 for all). There were no significant differences in the expression of GR or 5-HTR1A among the three treatment groups (P > 0.05).

CONCLUSION: Cake-separated moxibustion can regulate the expression of GR and 5-HTR1A in the hippocampus to accommodate the function of the limbic-hypothalamic-pituitary-adrenal axis to increase the gastric emptying rate of FD rats, and to improve the gastrointestinal motility as Xiaoyaosan and domperidone. This might be one of the mechanisms underlying the therapeutic effect of cake-separated moxibustion on FD.

Glucocorticoids and Stress-Induced Changes in the Expression of PERIOD1 in the Rat Forebrain

The secretion of glucocorticoids in mammals is under circadian control, but glucocorticoids themselves are also implicated in modulating circadian clock gene expression. We have shown that the expression of the circadian clock protein PER1 in the forebrain is modulated by stress, and that this effect is associated with changes in plasma corticosterone levels, suggesting a possible role for glucocorticoids in the mediation of stress-induced changes in the expression of PER1 in the brain. To study this, we assessed the effects of adrenalectomy and of pretreatment with the glucocorticoid receptor antagonist, mifepristone, on the expression of PER1 in select limbic and hypothalamic regions following acute exposure to a neurogenic stressor, restraint, or a systemic stressor, 2-Deoxy-D-glucose (2DG) in rats. Acute restraint suppressed PER1 expression in the oval nucleus of the bed nucleus of the stria terminalis (BNSTov) and the central nucleus of the amygdala (CEAl), whereas 2DG increased PER1 in both regions. Both stressors increased PER1 expression in the paraventricular (PVN) and dorsomedial (DMH) nuclei of the hypothalamus, and the piriform cortex (Pi). Adrenalectomy and pretreatment with mifepristone reversed the effects of both stressors on PER1 expression in the BNSTov and CEAl, and blocked their effects in the DMH. In contrast, both treatments enhanced the effects of restraint and 2DG on PER1 levels in the PVN. Stress-induced PER1 expression in the Pi was unaffected by either treatment. PER1 expression in the suprachiasmatic nucleus, the master circadian clock, was not altered by either exposure to stress or by the glucocorticoid manipulations. Together, the results demonstrate a key role for glucocorticoid signaling in stress-induced changes in PER1 expression in the brain.

Influence of restoration adjustments on prefrontal blood flow: A simplified NIRS preliminary study

Objective

The aim of this study was to examine, after setting several restorations, the influence of adjusted occlusal interference during gum chewing on blood flow in the prefrontal area as determined using near-infrared spectroscopy.

Material and methods

The physiological rate was assessed using a visual analog scale (VAS) questionnaire. We selected 16 patients who desired prosthetic restorative treatment on the lateral dentition, and eight healthy volunteers. Subjects were divided into three eight-person groups. One group received restorations on the premolar area (PA), another group received restorations on the molar area (MA), and the control group (CT) received no prosthetic restorations. The spectroscope was fastened to the frontal region of the head after placement of the final restoration, but before adjustment.

Results

Pre-adjustment (first gum chewing for CT) blood flow in the prefrontal cortex was measured during gum chewing. Blood flow was again measured during gum chewing after the restoration (second gum chewing for CT) had been adjusted in accordance with the subjective assessment of the patient while wearing the device. The VAS provided quantification of comfort during gum chewing before and after restoration adjustment. For the PA and MA groups, adjusting restorations decreased discomfort significantly during gum chewing. Moreover, in the MA group, prefrontal blood flow was significantly reduced, and blood flow correlated with discomfort.

Conclusions

Activation of the prefrontal area may provide an objective criterion for judging the functionality of occlusion after prosthetic occlusal reconstruction and/or orthodontics.

Differential activation of serotonergic neurons during short- and long-term gregarization of desert locusts

Serotonin is a neurochemical with evolutionarily conserved roles in orchestrating nervous system function and behavioural plasticity. A dramatic example is the rapid transformation of desert locusts from cryptic asocial animals into gregarious crop pests that occurs when drought forces them to accumulate on dwindling resources, triggering a profound alteration of behaviour within just a few hours. The onset of crowding induces a surge in serotonin within their thoracic ganglia that is sufficient and necessary to induce the switch from solitarious to gregarious behaviour. To identify the neurons responsible, we have analysed how acute exposure to three gregarizing stimuli--crowding, touching the hind legs or seeing and smelling other locusts--and prolonged group living affect the expression of serotonin in individual neurons in the thoracic ganglia. Quantitative analysis of cell body immunofluorescence revealed three classes of neurons with distinct expressional responses. All ganglia contained neurons that responded to multiple gregarizing stimuli with increased expression. A second class showed increased expression only in response to intense visual and olfactory stimuli from conspecifics. Prolonged group living affected a third and entirely different set of neurons, revealing a two-tiered role of the serotonergic system as both initiator and substrate of socially induced plasticity. This demonstrates the critical importance of ontogenetic time for understanding the function of serotonin in the reorganization of behaviour.

Stress-induced changes in the expression of the clock protein PERIOD1 in the rat limbic forebrain and hypothalamus: role of stress type, time of day, and predictability

Stressful events can disrupt circadian rhythms in mammals but mechanisms underlying this disruption remain largely unknown. One hypothesis is that stress alters circadian protein expression in the forebrain, leading to functional dysregulation of the brain circadian network and consequent disruption of circadian physiological and behavioral rhythms. Here we characterized the effects of several different stressors on the expression of the core clock protein, PER1 and the activity marker, FOS in select forebrain and hypothalamic nuclei in rats. We found that acute exposure to processive stressors, restraint and forced swim, elevated PER1 and FOS expression in the paraventricular and dorsomedial hypothalamic nuclei and piriform cortex but suppressed PER1 and FOS levels exclusively in the central nucleus of the amygdala (CEAl) and oval nucleus of the bed nucleus of the stria terminalis (BNSTov). Conversely, systemic stressors, interleukin-1β and 2-Deoxy-D-glucose, increased PER1 and FOS levels in all regions studied, including the CEAl and BNSTov. PER1 levels in the suprachiasmatic nucleus (SCN), the master pacemaker, were unaffected by any of the stress manipulations. The effect of stress on PER1 and FOS was modulated by time of day and, in the case of daily restraint, by predictability. These results demonstrate that the expression of PER1 in the forebrain is modulated by stress, consistent with the hypothesis that PER1 serves as a link between stress and the brain circadian network. Furthermore, the results show that the mechanisms that control PER1 and FOS expression in CEAl and BNSTov are uniquely sensitive to differences in the type of stressor. Finally, the finding that the effect of stress on PER1 parallels its effect on FOS supports the idea that Per1 functions as an immediate-early gene. Our observations point to a novel role for PER1 as a key player in the interface between stress and circadian rhythms.

Cytokines, prostaglandins and nitric oxide in the regulation of stress-response systems

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis is accepted as one of the fundamental biological mechanisms that underlie major depression. This hyperactivity is caused by diminished feedback inhibition of glucocorticoid (GC)-induced reduction of HPA axis signaling and increased corticotrophin-releasing hormone (CRH) secretion from the hypothalamic paraventricular nucleus (PVN) and extra-hypothalamic neurons. During chronic stress-induced inhibition of systemic feedback, cytosolic glucocorticoid receptor (GR) levels were significantly changed in the prefrontal cortex (PFC) and hippocampus, both structures known to be deeply involved in the pathogenesis of depression. Cytokines secreted by both immune and non-immune cells can markedly affect neurotransmission within regulatory brain circuits related to the expression of emotions; cytokines may also induce hormonal changes similar to those observed following exposure to stress. Proinflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) are implicated in the etiologies of clinical depression and anxiety disorders. Prolonged stress responses and cytokines impair neuronal plasticity and stimulation of neurotransmission. Exposure to acute stress and IL-1β markedly increased IL-1β levels in the PFC, hippocampus and hypothalamus, as well as overall HPA axis activity. Repeated stress sensitized the HPA axis response to IL-1β. Inflammatory responses in the brain contribute to cellular damage associated with neuropsychiatric diseases related to stress. Physical, psychological or combined-stress conditions evoke a proinflammatory response in the brain and other systems, characterized by a complex release of several inflammatory mediators including cytokines, prostanoids, nitric oxide (NO) and transcription factors. Induced CRH release involves IL-1, IL-6 and TNF-α, for stimulation adrenocorticotropic hormone (ACTH) release from the anterior pituitary. NO also participates in signal transduction pathways that result in the release of corticosterone from the adrenal gland. NO participates in multiple interactions between neuroendocrine and neuroimmune systems in physiological and pathological processes. Neuronal NO synthase (nNOS) modulates learning and memory and is involved in development of neuropsychiatric diseases, including depression. Nitric oxide generated in response to stress exposure is associated with depression-like and anxiety-like behaviors. In the central nervous system (CNS), prostaglandins (PG) generated by the cyclooxygenase (COX) enzyme are involved in the regulation of HPA axis activity. Prior exposure to chronic stress alters constitutive (COX-1) and inducible (COX-2) cyclooxygenase responses to homotypic stress differently in the PFC, hippocampus and hypothalamus. Both PG and NO generated within the PVN participate in this modulation. Acute stress affects the functionality of COX/PG and NOS/NO systems in brain structures. The complex responses of central and peripheral pathways to acute and chronic stress involve cytokines, NO and PG systems that regulate and turn off responses that would be potentially harmful for cellular homeostasis and overall health.