Mechanisms of stress in the brain

Hierarchical Status Predicts Behavioral Vulnerability and Nucleus Accumbens Metabolic Profile Following Chronic Social Defeat Stress

Extensive data highlight the existence of major differences in individuals' susceptibility to stress [1-4]. While genetic factors [5, 6] and exposure to early life stress [7, 8] are key components for such neurobehavioral diversity, intriguing observations revealed individual differences in response to stress in inbred mice [9-12]. This raised the possibility that other factors might be critical in stress vulnerability. A key challenge in the field is to identify non-invasively risk factors for vulnerability to stress. Here, we investigated whether behavioral factors, emerging from preexisting dominance hierarchies, could predict vulnerability to chronic stress [9, 13-16]. We applied a chronic social defeat stress (CSDS) model of depression in C57BL/6J mice to investigate the predictive power of hierarchical status to pinpoint which individuals will exhibit susceptibility to CSDS. Given that the high social status of dominant mice would be the one particularly challenged by CSDS, we predicted and found that dominant individuals were the ones showing a strong susceptibility profile as indicated by strong social avoidance following CSDS, while subordinate mice were not affected. Data from ¹H-NMR spectroscopy revealed that the metabolic profile in the nucleus accumbens (NAc) relates to social status and vulnerability to stress. Under basal conditions, subordinates show lower levels of energy-related metabolites compared to dominants. In subordinates, but not dominants, levels of these metabolites were increased after exposure to CSDS. To the best of our knowledge, this is the first study that identifies non-invasively the origin of behavioral risk factors predictive of stress-induced depression-like behaviors associated with metabolic changes.

Role of the lateral habenula in memory through online processing of information

Our memory abilities, whether they involve short-term working memory or long-term episodic or procedural memories, are essential for our well-being, our capacity to adapt to constraints of our environment and survival. Therefore, several key brain regions and neurotransmitter systems are engaged in the processing of sensory information to either maintain such information in working memory so that it will quickly be used, and/or participate in the elaboration and storage of enduring traces useful for longer periods of time. Animal research has recently attracted attention on the lateral habenula which, as shown in rodents and non-human primates, seems to process information stemming in the main regions involved in memory processing, e.g., the medial prefrontal cortex, the hippocampus, the amygdala, the septal region, the basal ganglia, and participates in the control of key memory-related neurotransmitters systems, i.e., dopamine, serotonin, acetylcholine. Recently, the lateral habenula has been involved in working and spatial reference memories, in rodents, likely by participating in online processing of contextual information. In addition, several behavioral studies strongly suggest that it is also involved in the processing of the emotional valance of incoming information in order to adapt to particularly stressful situations. Therefore, the lateral habenula appears like a key region at the interface between cognition and emotion to participate in the selection of appropriate behaviors.

Selective attenuation of electrophysiological activity of the dentate gyrus in a social defeat mouse model

Current research on stress pathology has revealed a set of molecular and cellular mechanisms through which psychosocial stress impairs brain function. However, there are few studies that have examined how chronic stress exposure alters neuronal activity patterns at a network level. Here, we recorded ensemble neuronal activity patterns of the cortico-hippocampal network from urethane-anesthetized mice that were subjected to repeated social defeat stress. In socially defeated mice, the magnitudes of local field potential signals, including theta, slow gamma, and fast gamma oscillations, were significantly reduced in the dentate gyrus, whereas they remained unchanged in the hippocampus and somatosensory cortex. In accordance with the vast majority of histological and biochemical studies, our evidence from electrophysiological investigations highlights the dentate gyrus as a key brain area that is primarily susceptible to stress-induced dysfunction.

The Nucleus Accumbens and Ketamine Treatment in Major Depressive Disorder

Animal models of depression repeatedly showed stress-induced nucleus accumbens (NAc) hypertrophy. Recently, ketamine was found to normalize this stress-induced NAc structural growth. Here, we investigated NAc structural abnormalities in major depressive disorder (MDD) in two cohorts. Cohort A included a cross-sectional sample of 34 MDD and 26 healthy control (HC) subjects, with high-resolution magnetic resonance imaging (MRI) to estimate NAc volumes. Proton MR spectroscopy (¹H MRS) was used to divide MDD subjects into two subgroups: glutamate-based depression (GBD) and non-GBD. A separate longitudinal sample (cohort B) included 16 MDD patients who underwent MRI at baseline then 24 h following intravenous infusion of ketamine (0.5 mg/kg). In cohort A, we found larger left NAc volume in MDD compared to controls (Cohen's d=1.05), but no significant enlargement in the right NAc (d=0.44). Follow-up analyses revealed significant subgrouping effects on the left (d⩾1.48) and right NAc (d⩾0.95) with larger bilateral NAc in non-GBD compared to GBD and HC. NAc volumes were not different between GBD and HC. In cohort B, ketamine treatment reduced left NAc, but increased left hippocampal, volumes in patients achieving remission. The cross-sectional data provided the first evidence of enlarged NAc in patients with MDD. These NAc abnormalities were limited to patients with non-GBD. The pilot longitudinal data revealed a pattern of normalization of left NAc and hippocampal volumes particularly in patients who achieved remission following ketamine treatment, an intriguing preliminary finding that awaits replication.

Adenosine A2A receptor regulation of microglia morphological remodeling-gender bias in physiology and in a model of chronic anxiety

Developmental risk factors, such as the exposure to stress or high levels of glucocorticoids (GCs), may contribute to the pathogenesis of anxiety disorders. The immunomodulatory role of GCs and the immunological fingerprint found in animals prenatally exposed to GCs point towards an interplay between the immune and the nervous systems in the etiology of these disorders. Microglia are immune cells of the brain, responsive to GCs and morphologically altered in stress-related disorders. These cells are regulated by adenosine A_2A receptors, which are also involved in the pathophysiology of anxiety. We now compare animal behavior and microglia morphology in males and females prenatally exposed to the GC dexamethasone. We report that prenatal exposure to dexamethasone is associated with a gender-specific remodeling of microglial cell processes in the prefrontal cortex: males show a hyper-ramification and increased length whereas females exhibit a decrease in the number and in the length of microglia processes. Microglial cells re-organization responded in a gender-specific manner to the chronic treatment with a selective adenosine A_2A receptor antagonist, which was able to ameliorate microglial processes alterations and anxiety behavior in males, but not in females.

Moderate within-person variability in cortisol is related to executive function in early childhood

Lab-based experimental studies with humans and in animal models demonstrate that the relation between glucocorticoid (GC) levels and performance on measures of higher-order cognitive ability such as executive function (EF) is best described by an inverted U-shape curve. Moderate levels of GCs (cortisol/corticosterone) are associated with comparatively better performance relative to GC levels that are particularly high or low. Although findings from experimental studies are definitive and have high internal validity, the external validity of this association as an aspect of children's development is unknown. Here we analyze data from the Family Life Project (N=1292), a prospective longitudinal sample of children and families in predominantly low-income and rural communities followed longitudinally from infancy through age 60 months. Consistent with the prior experimental literature, we found evidence of an inverted-U relation. For children with relatively low cortisol levels, on average, between the ages 7, 15, 24, and 48 months, those illustrating moderate fluctuations in their cortisol levels over this span tended to show subsequently better EF performance at 60 months, than did children with either highly stable or highly variable temporal profiles. This curvilinear function did not extend to children whose cortisol levels were high, on average. These children tended to show lower EF performance, irrespective the stability of their cortisol levels over time.

Erbb4 Deletion from Medium Spiny Neurons of the Nucleus Accumbens Core Induces Schizophrenia-Like Behaviors via Elevated GABAA Receptor α1 Subunit Expression

Medium spiny neurons (MSNs), the major GABAergic projection neurons in the striatum, are implicated in many neuropsychiatric diseases such as schizophrenia, but the underlying mechanisms remain unclear. We found that a deficiency in Erbb4, a schizophrenia risk gene, in MSNs of the nucleus accumbens (NAc) core, but not the dorsomedial striatum, markedly induced schizophrenia-like behaviors such as hyperactivity, abnormal marble-burying behavior, damaged social novelty recognition, and impaired sensorimotor gating function in male mice. Using immunohistochemistry, Western blot, RNA interference, electrophysiology, and behavior test studies, we found that these phenomena were mediated by increased GABA_A receptor α1 subunit (GABA_AR α1) expression, which enhanced inhibitory synaptic transmission on MSNs. These results suggest that Erbb4 in MSNs of the NAc core may contribute to the pathogenesis of schizophrenia by regulating GABAergic transmission and raise the possibility that GABA_AR α1 may therefore serve as a new therapeutic target for schizophrenia.SIGNIFICANCE STATEMENT Although ErbB4 is highly expressed in striatal medium spiny neurons (MSNs), its role in this type of neuron has not been reported previously. The present study demonstrates that Erbb4 deletion in nucleus accumbens (NAc) core MSNs can induce schizophrenia-like behaviors via elevated GABA_A receptor α1 subunit (GABA_AR α1) expression. To our knowledge, this is the first evidence that ErbB4 signaling in the MSNs is involved in the pathology of schizophrenia. Furthermore, restoration of GABA_AR α1 in the NAc core, but not the dorsal medium striatum, alleviated the abnormal behaviors. Here, we highlight the role of the NAc core in the pathogenesis of schizophrenia and suggest that GABA_AR α1 may be a potential pharmacological target for its treatment.

Synaptic functions of endocannabinoid signaling in health and disease

Endocannabinoids (eCBs) are a family of lipid molecules that act as key regulators of synaptic transmission and plasticity. They are synthetized "on demand" following physiological and/or pathological stimuli. Once released from postsynaptic neurons, eCBs typically act as retrograde messengers to activate presynaptic type 1 cannabinoid receptors (CB₁) and induce short- or long-term depression of neurotransmitter release. Besides this canonical mechanism of action, recent findings have revealed a number of less conventional mechanisms by which eCBs regulate neural activity and synaptic function, suggesting that eCB-mediated plasticity is mechanistically more diverse than anticipated. These mechanisms include non-retrograde signaling, signaling via astrocytes, participation in long-term potentiation, and the involvement of mitochondrial CB₁. Focusing on paradigmatic brain areas, such as hippocampus, striatum, and neocortex, we review typical and novel signaling mechanisms, and discuss the functional implications in normal brain function and brain diseases. In summary, eCB signaling may lead to different forms of synaptic plasticity through activation of a plethora of mechanisms, which provide further complexity to the functional consequences of eCB signaling. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Early adversity and brain response to faces in young adulthood

Early stressors play a key role in shaping interindividual differences in vulnerability to various psychopathologies, which according to the diathesis-stress model might relate to the elevated glucocorticoid secretion and impaired responsiveness to stress. Furthermore, previous studies have shown that individuals exposed to early adversity have deficits in emotion processing from faces. This study aims to explore whether early adversities associate with brain response to faces and whether this association might associate with the regional variations in mRNA expression of the glucocorticoid receptor gene (NR3C1). A total of 104 individuals drawn from the Northern Finland Brith Cohort 1986 participated in a face-task functional magnetic resonance imaging (fMRI) study. A large independent dataset (IMAGEN, N = 1739) was utilized for reducing fMRI data-analytical space in the NFBC 1986 dataset. Early adversities were associated with deviant brain response to fearful faces (MANCOVA, P = 0.006) and with weaker performance in fearful facial expression recognition (P = 0.01). Glucocorticoid receptor gene expression (data from the Allen Human Brain Atlas) correlated with the degree of associations between early adversities and brain response to fearful faces (R²  = 0.25, P = 0.01) across different brain regions. Our results suggest that early adversities contribute to brain response to faces and that this association is mediated in part by the glucocorticoid system. Hum Brain Mapp 38:4470-4478, 2017. © 2017 Wiley Periodicals, Inc.

Predicting attention-deficit/hyperactivity disorder severity from psychosocial stress and stress-response genes: a random forest regression approach

Identifying genetic variants contributing to attention-deficit/hyperactivity disorder (ADHD) is complicated by the involvement of numerous common genetic variants with small effects, interacting with each other as well as with environmental factors, such as stress exposure. Random forest regression is well suited to explore this complexity, as it allows for the analysis of many predictors simultaneously, taking into account any higher-order interactions among them. Using random forest regression, we predicted ADHD severity, measured by Conners' Parent Rating Scales, from 686 adolescents and young adults (of which 281 were diagnosed with ADHD). The analysis included 17 374 single-nucleotide polymorphisms (SNPs) across 29 genes previously linked to hypothalamic-pituitary-adrenal (HPA) axis activity, together with information on exposure to 24 individual long-term difficulties or stressful life events. The model explained 12.5% of variance in ADHD severity. The most important SNP, which also showed the strongest interaction with stress exposure, was located in a region regulating the expression of telomerase reverse transcriptase (TERT). Other high-ranking SNPs were found in or near NPSR1, ESR1, GABRA6, PER3, NR3C2 and DRD4. Chronic stressors were more influential than single, severe, life events. Top hits were partly shared with conduct problems. We conclude that random forest regression may be used to investigate how multiple genetic and environmental factors jointly contribute to ADHD. It is able to implicate novel SNPs of interest, interacting with stress exposure, and may explain inconsistent findings in ADHD genetics. This exploratory approach may be best combined with more hypothesis-driven research; top predictors and their interactions with one another should be replicated in independent samples.

Psychiatric Hospitalization Increases Short-Term Risk of Stroke

BACKGROUND AND PURPOSE

Recent evidence suggests that psychological distress, including the symptoms of psychiatric illness, may acutely increase the risk of stroke. However, existing studies are limited by small sample sizes, inherent recall bias, and poorly defined criteria for what constitutes psychological distress.

METHODS

We analyzed administrative data from the Healthcare Cost and Utilization Project for the state of California from 2007 to 2009 using a case-crossover design. Conditional logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (95% CIs) for combined hemorrhagic and ischemic stroke risk occurring within 15, 30, 90, 180, and 365 days of a hospitalization for a psychiatric diagnosis (as defined by International Classification of Diseases, Ninth Revision, code) among adults.

RESULTS

Psychiatric hospitalizations within 1 year before stroke were found in 2585 (5.3%) of 48 558 stroke patients. Hospitalization for a psychiatric condition was associated with increased risk of stroke within all 5 time periods, with the highest odds of stroke occurring within 15 days (0-15 days: OR, 3.5; 95% confidence interval [CI], 2.6-4.8; 0-30 days: OR, 3.0; 95% CI, 2.4-3.8; 0-90 days: OR, 2.3; 95% CI, 2.0-2.7; 0-180 days: OR, 2.2; 95% CI, 2.0-2.5; and 0-365 days: OR, 2.6; 95% CI, 2.4-2.8).

CONCLUSIONS

Psychiatric hospitalization increases the short-term risk of stroke, particularly within the 15-day period after hospitalization.

Beneficial effect of fluoxetine treatment aganist psychological stress is mediated by increasing BDNF expression in selected brain areas

SSRI antidepressant fluoxetine is widely used to treat psychological stress related disorders, however the underlying working mechanisms is not fully understood, as SSRIs can rapidly increase the extracellular serotonin levels but it normally takes weeks to reveal their therapeutic effect in the stress-related psychological disorders. Our previous study demonstrated that purely psychological stress without any physic stimuli induces a biphasic change in the expression of brain-derived neurotrophic factor (BDNF), which immediately decrease and then gradually increase after the stress; and that the latter BDNF increase in response to the psychological stress involves the activation of serotonin system. To investigate the role of BDNF in the fluoxetine treatment for stress-related psychological disorders, we examined the mRNA and protein levels of BDNF in the brain of Sprague-Dawley (SD) rats, which were pretreated with fluoxetine at 10 mg/kg or vehicle solution for 14 days, over 24 hour after an acute psychological stress exposure. In situ hybridization and immunohistochemistry were performed to detect the expression of BDNF at different time points in various brain regions after the psychological stress. We found that fluoxetine treatment completely blocked the BDNF decrease induced by the psychological stress, and also enhanced the gradual increase in the expression of BDNF in most of the brain regions except VTA after the psychological stress. The results suggest that the enhancement in BDNF levels induced by chronic fluoxetine treatment mediates the therapeutic effect against psychological stress.

Academic stress and personality interact to increase the neural response to high-calorie food cues

Psychosocial stress is associated with an increased intake of palatable foods and weight gain in stress-reactive individuals. Personality traits have been shown to predict stress-reactivity. However, it is not known if personality traits influence brain activity in regions implicated in appetite control during psychosocial stress. The current study assessed whether Gray's Behavioural Inhibition System (BIS) scale, a measure of stress-reactivity, was related to the activity of brain regions implicated in appetite control during a stressful period. Twenty-two undergraduate students participated in a functional magnetic resonance imaging (fMRI) experiment once during a non-exam period and once during final exams in a counter-balanced order. In the scanner, they viewed food and scenery pictures. In the exam compared with the non-exam condition, BIS scores related to increased perceived stress and correlated with increased blood-oxygen-level dependent (BOLD) response to high-calorie food images in regions implicated in food reward and subjective value, such as the ventromedial prefrontal cortex, (vmPFC) and the amygdala. BIS scores negatively related to the functional connectivity between the vmPFC and the dorsolateral prefrontal cortex. The results demonstrate that the BIS trait influences stress reactivity. This is observed both as an increased activity in brain regions implicated in computing the value of food cues and decreased connectivity of these regions to prefrontal regions implicated in self-control. This suggests that the effects of real life stress on appetitive brain function and self-control is modulated by a personality trait. This may help to explain why stressful periods can lead to overeating in vulnerable individuals.

Anxiety disorders

Anxiety disorders constitute the largest group of mental disorders in most western societies and are a leading cause of disability. The essential features of anxiety disorders are excessive and enduring fear, anxiety or avoidance of perceived threats, and can also include panic attacks. Although the neurobiology of individual anxiety disorders is largely unknown, some generalizations have been identified for most disorders, such as alterations in the limbic system, dysfunction of the hypothalamic-pituitary-adrenal axis and genetic factors. In addition, general risk factors for anxiety disorders include female sex and a family history of anxiety, although disorder-specific risk factors have also been identified. The diagnostic criteria for anxiety disorders varies for the individual disorders, but are generally similar across the two most common classification systems: the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) and the International Classification of Diseases, Tenth Edition (ICD-10). Despite their public health significance, the vast majority of anxiety disorders remain undetected and untreated by health care systems, even in economically advanced countries. If untreated, these disorders are usually chronic with waxing and waning symptoms. Impairments associated with anxiety disorders range from limitations in role functioning to severe disabilities, such as the patient being unable to leave their home.

Neural stress reactivity relates to smoking outcomes and differentiates between mindfulness and cognitive-behavioral treatments

Stress and negative affect are known contributors to drug use and relapse, and several known treatments for addictions include strategies for managing them. In the current study, we administered a well-established stress provocation during functional magnetic resonance imaging (fMRI) to 23 participants who completed either mindfulness training (MT; N=11) or the American Lung Association's Freedom From Smoking (FFS; N=12), which is a cognitive-behavioral treatment (CBT) for smoking cessation. Across the entire sample, we found that stress reactivity in several brain regions including the amygdala and anterior/mid insula was related to reductions in smoking after treatment, as well as at 3-month post-treatment follow-up. Moreover, conjunction analysis revealed that these same regions also differentiated between treatment groups such that the MT group showed lower stress-reactivity compared to the FFS/CBT group. This suggests that reduction in stress reactivity may be one of the mechanisms that underlie the efficacy of MT in reducing smoking over time. The findings have important implications for our understanding of stress, the neural and psychological mechanisms that underlie mindfulness-based treatments, and for smoking cessation treatments more broadly.

How do antidepressants work? New perspectives for refining future treatment approaches

Most currently available antidepressants target monoamine neurotransmitter function. However, a purely neurotransmitter-based explanation for antidepressant drug action is challenged by the delayed clinical onset of most agents and the need to explain how neurochemical changes reverse the many different symptoms of depression. Novel approaches to understanding of antidepressant drug action include a focus on early changes in emotional and social processing and the role of neural plasticity. In this Review, we discuss the ways in which these two different theories reflect different or complementary approaches, and how they might be integrated to offer novel solutions for people with depression. We consider the predictions made by these mechanistic approaches for the stratification and development of new therapeutics for depression, and the next steps that need to be made to facilitate this translation of science to the clinic.

Epigenetic mechanisms of alcoholism and stress-related disorders

Stress-related disorders, such as anxiety, early life stress, and posttraumatic stress disorder appear to be important factors in promoting alcoholism, as alcohol consumption can temporarily attenuate the negative affective symptoms of these disorders. Several molecules involved in signaling pathways may contribute to the neuroadaptation induced during alcohol dependence and stress disorders, and among these, brain-derived neurotrophic factor (BDNF), corticotropin releasing factor (CRF), neuropeptide Y (NPY) and opioid peptides (i.e., nociceptin and dynorphin) are involved in the interaction of stress and alcohol. In fact, alterations in the expression and function of these molecules have been associated with the pathophysiology of stress-related disorders and alcoholism. In recent years, various studies have focused on the epigenetic mechanisms that regulate chromatin architecture, thereby modifying gene expression. Interestingly, epigenetic modifications in specific brain regions have been shown to be associated with the neurobiology of psychiatric disorders, including alcoholism and stress. In particular, the enzymes responsible for chromatin remodeling (i.e., histone deacetylases and methyltransferases, DNA methyltransferases) have been identified as common molecular mechanisms for the interaction of stress and alcohol and have become promising therapeutic targets to treat or prevent alcoholism and associated emotional disorders.

Environmental and hormonal regulation of epigenetic enzymes in the hypothalamus

Neuroendocrine structures integrate a vast range of external cues and internal signals that, in turn, result in adaptive physiological responses. Emerging data indicate that light, social cues, stress and energy balance stimulate relatively short- and long-term genomic modifications in discrete neuroendocrine structures, which are mediated by epigenetic mechanisms. Moreover, environmentally-induced fluctuations in the synthesis of local hypothalamic and circulating hormones provide an internal signal that contributes to the extensive neuroendocrine genomic plasticity. This review examines the impact of environmental stimuli and endogenous hormonal signals on the regulation of epigenetic enzymes in key neuroendocrine structures. The data discussed are predominantly derived from studies in the neuroendocrine control of seasonal reproduction and the impact of social stress in rodent models. The perspective presented considers the role of oestrogen and glucocorticoids as the primary catalysts for inducing epigenetic modifications (eg, DNA methylation) in specific neuroendocrine structures. Oestrogen and glucocorticoid actions suggest: (i) a preferential action for specific epigenetic enzymes and (ii) nucleus- and cell-specific modifications. Untangling the complex web of hormonal regulation of methylation and acetylation will enhance our understanding of short- and long-term changes in epigenetic enzymes that generate adaptive and pathological neuroendocrine responses.

Effect of stress on human biology: Epigenetics, adaptation, inheritance, and social significance

I present a brief introduction to epigenetics, focused primarily on methylation of the genome and various regulatory RNAs, modifications of associated histones, and their importance in enabling us to adapt to real and changing environmental, developmental, and social circumstances. Following this is a more extensive overview of how it impacts our inheritance, our entire life (which changes as we age), and how we interact with others. Throughout, I emphasize the critical influence that stress, of many varieties exerts, via epigenetic means, on much of how we live and survive, mostly in the brain. I end with a short section on multigenerational transmission, drugs, and the importance of both social life and early life experiences in the development of adult diseases. There will be nothing about cancer. Although epigenetics is critical in that field, it is a whole different cobweb of complications (some involving stress).

Emerging Role for Nucleus Accumbens Medium Spiny Neuron Subtypes in Depression

The ventral striatum (nucleus accumbens) and its role in mood, reward, and motivation has been the focus of significant research. Despite this interest, little work has addressed cell type-specific distinctions in medium spiny neurons (MSNs), the main projection neurons in the nucleus accumbens and dorsal striatum, and their function in relation to stress and depression. Previous work has shown opposing roles for D₁ and D₂ receptor MSN subtypes in depression-like outcomes to stress, particularly in regard to repeated neuronal stimulation and excitatory transmission. Yet the mechanisms of action are still unknown. We discuss potential mechanisms by which MSN subtype function promotes dichotomous behavioral outcomes caused by differences in cellular plasticity, subcellular signaling pathways, and genetic expression. This review aims to address our current understanding about the role of nucleus accumbens MSN subtypes in stress-related depression behavior and speculates on how currently understood mechanisms contribute to factors that control the activity of MSNs.

Methyl CpG level at distal part of heat-shock protein promoter HSP70 exhibits epigenetic memory for heat stress by modulating recruitment of POU2F1-associated nucleosome-remodeling deacetylase (NuRD) complex

Depending on its stringency, exposure to heat in early life leads to either resilience or vulnerability to heat stress later in life. We hypothesized that epigenetic alterations in genes belonging to the cell proteostasis pathways are attributed to long-term responses to heat stress. Epigenetic regulation of the mRNA expression of the molecular chaperone heat-shock protein (HSP) 70 (HSPA2) was evaluated in the chick hypothalamus during the critical period of thermal-control establishment on day 3 post-hatch and during heat challenge on day 10. Both the level and duration of HSP70 expression during heat challenge a week after heat conditioning were more pronounced in chicks conditioned under harsh versus mild temperature. Analyzing different segments of the promoter in vitro indicated that methylation of a distal part altered its transcriptional activity. In parallel, DNA-methylation level of this segment in vivo was higher in harsh- compared to mild-heat-conditioned chicks. Hypermethylation of the HSP70 promoter in high-temperature-conditioned chicks was accompanied by a reduction in both POU Class 2 Homeobox 1 (POU2F1) binding and recruitment of the nucleosome remodeling deacetylase (NuRD) chromatin-remodeling complex. As a result, histone H3 acetylation levels at the HSP70 promoter were higher in harsh-temperature-conditioned chicks than in their mild-heat-conditioned counterparts. These results suggest that methylation level of a distal part of the HSP70 promoter and POU2F1 recruitment may reflect heat-stress-related epigenetic memory and may be useful in differentiating between individuals that are resilient or vulnerable to stress.

Role of glial cell line-derived neurotrophic factor in the pathogenesis and treatment of mood disorders

Glial cell line-derived neurotrophic factor (GDNF) is widely recognized as a survival factor for dopaminergic neurons, but GDNF has also been shown to promote development, differentiation, and protection of other central nervous system neurons and was thought to play an important role in various neuropsychiatric disorders. Severe mood disorders, such as primarily major depressive disorder and bipolar affective disorder, attract particular attention. These psychopathologies are characterized by structural alterations accompanied by the dysregulation of neuroprotective and neurotrophic signaling mechanisms required for the maturation, growth, and survival of neurons and glia. The main objective of this review is to summarize the recent findings and evaluate the potential role of GDNF in the pathogenesis and treatment of mood disorders. Specifically, it describes (1) the implication of GDNF in the mechanism of depression and in the effect of antidepressant drugs and mood stabilizers and (2) the interrelation between GDNF and brain neurotransmitters, playing a key role in the pathogenesis of depression. This review provides converging lines of evidence that (1) brain GDNF contributes to the mechanism underlying depressive disorders and the effect of antidepressants and mood stabilizers and (2) there is a cross-talk between GDNF and neurotransmitters representing a feedback system: GDNF-neurotransmitters and neurotransmitters-GDNF.

Integrative medicine: Breaking down silos of knowledge and practice an epigenetic approach

The future of medicine is discussed in the context of epigenetic influences during the entire life course and the lived experiences of each person, avoiding as much as possible the "medicalization" of the individual and taking a more humanistic view. The reciprocal communication between brain and body via the neuroendocrine, autonomic, metabolic and immune systems and the plasticity of brain architecture provide the basis for devising better "top down" interventions that engage the whole person in working towards his or her welfare. The life course perspective emphasizes the importance of intervening early in life to prevent adverse early life experiences, including the effects of poverty, that can have lifelong consequences, referred to as "biological embedding". In the spirit of integrative, humanistic medicine, treatments that "open windows of plasticity" allow targeted behavioral interventions to redirect brain and body functions and behavior in healthier directions. Policies of government and the private sector, particularly at the local, community level, can create a supporting environment for such interventions. See "Common Ground for Health: Personalized, Precision and Social Medicine McEwen & Getz - https://www.youtube.com/watch?v=IRy_uUWyrEw.

Academic stress disrupts cortical plasticity in graduate students

Medical education is a time of high stress and anxiety for many graduate students in medical professions. In this study, we sought to investigate the effect of academic stress on cortical excitability and plasticity by using transcranial magnetic stimulation (TMS). We tested two groups (n = 13 each) of healthy graduate medical students (mean age 33.7 ± 3.8 SE). One group was tested during a final exam week (High-stress group) while the other group was tested after a break, during a week without exams (Low-stress group). Students were required to fill the Perceived Stress Scale-10 (PSS) questionnaire. We investigated resting motor threshold (RMT), motor evoked potential (MEP) amplitude and cortical silent period (CSP). The paired-pulse stimulation paradigm was used to assess short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Long-term potentiation (LTP)-like plasticity was evaluated with paired associative stimulation (PAS-25). There was no between-group difference in cortical excitability. On the contrary, during examination period, levels of perceived stress were significantly higher (p= .036) and the amount of cortical plasticity (60 min after PAS) was significantly lower (p = .029). LTP-like plasticity (60 min after PAS) was inversely correlated with perceived stress in the High-stress group. The present study showed LTP-like plasticity was reduced by examining stress in graduate students. Our results provide a new opportunity to objectively quantify the negative effect of academic and examination stress on brain plasticity.

Cortisol and DHEA in development and psychopathology

Dehydroepiandrosterone (DHEA) and cortisol are the most abundant hormones of the human fetal and adult adrenals released as end products of a tightly coordinated endocrine response to stress. Together, they mediate short- and long-term stress responses and enable physiological and behavioral adjustments necessary for maintaining homeostasis. Detrimental effects of chronic or repeated elevations in cortisol on behavioral and emotional health are well documented. Evidence for actions of DHEA that offset or oppose those of cortisol has stimulated interest in examining their levels as a ratio, as an alternate index of adrenocortical activity and the net effects of cortisol. Such research necessitates a thorough understanding of the co-actions of these hormones on physiological functioning and in association with developmental outcomes. This review addresses the state of the science in understanding the role of DHEA, cortisol, and their ratio in typical development and developmental psychopathology. A rationale for studying DHEA and cortisol in concert is supported by physiological data on the coordinated synthesis and release of these hormones in the adrenal and by their opposing physiological actions. We then present evidence that researching cortisol and DHEA necessitates a developmental perspective. Age-related changes in DHEA and cortisol are described from the perinatal period through adolescence, along with observed associations of these hormones with developmental psychopathology. Along the way, we identify several major knowledge gaps in the role of DHEA in modulating cortisol in typical development and developmental psychopathology with implications for future research.

Stressed and Inflamed, Can GSK3 Be Blamed?

Psychological stress has a pervasive influence on our lives. In many cases adapting to stress strengthens organisms, but chronic or severe stress is usually harmful. One surprising outcome of psychological stress is the activation of an inflammatory response that resembles inflammation caused by infection or trauma. Excessive psychological stress and the consequential inflammation in the brain can increase susceptibility to psychiatric diseases, such as depression, and impair learning and memory, including in some patients with cognitive deficits. An emerging target to control detrimental outcomes of stress and inflammation is glycogen synthase kinase-3 (GSK3). GSK3 promotes inflammation, partly by regulating key transcription factors in the inflammation signaling pathway, and GSK3 can impair learning by promoting inflammation and by inhibiting long-term potentiation (LTP). Drugs inhibiting GSK3 may prove beneficial for controlling mood and cognitive impairments caused by excessive stress and the associated neuroinflammation.

Maternal psychological stress-induced developmental disability, neonatal mortality and stillbirth in the offspring of Wistar albino rats

Background

Stress is an inevitable part of life, and maternal stress during the gestational period has dramatic effects in the early programming of the physiology and behavior of offspring. The developmental period is crucial for the well-being of the offspring. Prenatal stress influences the developmental outcomes of the fetus, in part because the developing brain is particularly vulnerable to stress. The etiology of birth defects of the offspring is reported to be 30–40% genetic and 7–10% multifactorial, with the remaining 50% still unknown and also there is no clear cause for neonatal mortality and still-birth.

Objective

The present study explores the association of maternal psychological stress on mother and the offspring’s incidence of birth defects, stillbirth, and neonatal mortality.

Study design

Pregnant animals were restrained to induce psychological stress (3 times per day, 45 minutes per session). Except control group, other animals were exposed to restraint stress during the gestational period: early gestational stress (EGS, stress exposure during 1^st day to 10^th days of gestational period), late gestational stress (LGS, stress exposure during 11^th day to till parturition), and full term gestational stress (FGS, stress exposure to the whole gestational period). The effects of maternal stress on the mother and their offspring were analyzed.

Results

Expectant female rats exposed to stress by physical restraint showed decreased body weight gain, food intake, and fecal pellet levels. Specifically, the offspring of female rats subjected to late gestational and full term gestational restraint stress showed more deleterious effects, such as physical impairment (LGS 24.44%, FGS 10%), neonatal mortality (EGS 2.56%, LGS 24.44%, FGS 17.5%), stillbirths (FGS 27.5%), low birth weight (EGS 5.42g, LGS 4.40g, FGS 4.12g), preterm births (EGS 539 Hrs, LGS 514 Hrs, FGS 520.6 Hrs), and delayed eyelid opening (EGS 15.16 Days, LGS 17 Days, FGS 17.67 Days).

Conclusion

The results of this study reveal that maternal stress may be associated with the offspring’s abnormal structural phenotyping, preterm birth, stillbirth and neonatal mortality.

Restraint Stress during Pregnancy Rapidly Raises Kynurenic Acid Levels in Mouse Placenta and Fetal Brain

Stressful events during pregnancy adversely affect brain development and may increase the risk of psychiatric disorders later in life. Early changes in the kynurenine (KYN) pathway (KP) of tryptophan (TRP) degradation, which contains several neuroactive metabolites, including kynurenic acid (KYNA), 3-hydroxykynurenine (3-HK), and quinolinic acid (QUIN), may constitute a molecular link between prenatal stress and delayed pathological consequences. To begin testing this hypothesis experimentally, we examined the effects of a 2-h restraint stress on KP metabolism in pregnant FVB/N mice on gestational day 17. TRP, KYN, KYNA, 3-HK, and QUIN levels were measured in maternal and fetal plasma and brain, as well as in the placenta, immediately after stress termination and 2 h later. In the same animals, we determined the activity of TRP 2,3-dioxygenase (TDO) in the maternal liver and in the placenta. Compared to unstressed controls, mostly transient changes in KP metabolism were observed in all of the tissues examined. Specifically, stress caused significant elevations of KYNA levels in the maternal plasma, placenta, and fetal brain, and also resulted in increased levels of TRP and KYN in the placenta, fetal plasma, and fetal brain. In contrast, 3-HK and QUIN levels remained unchanged from control values in all tissues at any time point. In the maternal liver, TDO activity was increased 2 h after stress cessation. Taken together, these findings indicate that an acute stress during the late gestational period preferentially affects the KYNA branch of KP metabolism in the fetal brain. Possible long-term consequences for postnatal brain development and pathology remain to be examined.

The role of epigenetics in social psychiatry

BACKGROUND

Epigenetics refers to the study of heritable changes in gene expression not involving changes in DNA sequence and is presently an active area of research in biology and medicine. There is increasing evidence that epigenetics is involved in the pathogenesis of psychiatric disorders.

AIMS AND METHODS

Several studies conducted to date have suggested that psychosocial factors act by modifying epigenetic mechanisms of gene expression in the brain in the pathogenesis of psychiatric disorders. Such studies have been conducted both on brain tissues and also using peripheral tissues as substitutes for brain tissues. This article reviews such studies.

RESULTS AND CONCLUSION

Epigenetic mechanisms of gene expression in the brain appear to link one individual with another in the context of social psychiatry. Epigenetics appears to be of major importance to the field of social psychiatry.

Anterior hippocampal dysconnectivity in posttraumatic stress disorder: a dimensional and multimodal approach

The anterior hippocampus (aHPC) has a central role in the regulation of anxiety-related behavior, stress response, emotional memory and fear. However, little is known about the presence and extent of aHPC abnormalities in posttraumatic stress disorder (PTSD). In this study, we used a multimodal approach, along with graph-based measures of global brain connectivity (GBC) termed functional GBC with global signal regression (f-GBCr) and diffusion GBC (d-GBC), in combat-exposed US Veterans with and without PTSD. Seed-based aHPC anatomical connectivity analyses were also performed. A whole-brain voxel-wise data-driven investigation revealed a significant association between elevated PTSD symptoms and reduced medial temporal f-GBCr, particularly in the aHPC. Similarly, aHPC d-GBC negatively correlated with PTSD severity. Both functional and anatomical aHPC dysconnectivity measures remained significant after controlling for hippocampal volume, age, gender, intelligence, education, combat severity, depression, anxiety, medication status, traumatic brain injury and alcohol/substance comorbidities. Depression-like PTSD dimensions were associated with reduced connectivity in the ventromedial and dorsolateral prefrontal cortex. In contrast, hyperarousal symptoms were positively correlated with ventromedial and dorsolateral prefrontal connectivity. We believe the findings provide first evidence of functional and anatomical dysconnectivity in the aHPC of veterans with high PTSD symptomatology. The data support the putative utility of aHPC connectivity as a measure of overall PTSD severity. Moreover, prefrontal global connectivity may be of clinical value as a brain biomarker to potentially distinguish between PTSD subgroups.

Immunometabolic dysregulation is associated with reduced cortical thickness of the anterior cingulate cortex

BACKGROUND

Immunometabolic dysregulation (low-grade inflammation and metabolic dysregulation) has been associated with the onset and more severe course of multiple psychiatric disorders, partly due to neuroanatomical changes and impaired neuroplasticity. We examined the effect of multiple markers of immunometabolic dysregulation on hippocampal and amygdala volume and anterior cingulate cortex thickness in a large sample of patients with depression and/or anxiety and healthy subjects (N=283).

METHODS

Interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-a), c-reactive protein (CRP), triglyceride levels and HDL-cholesterol and genomic profile risk scores (GPRS) for immunometabolic dysregulation were determined in peripheral blood and T1 MRI scans were acquired at 3T. Regional brain volume and cortical thickness was assessed using FreeSurfer. Covariate-adjusted linear regression analyses were performed to examine the relationship between immunometabolic dysregulation and brain volume/thickness across all subjects.

RESULTS

Multiple immunometabolic dysregulation markers (i.e. triglyceride levels and inflammation) were associated with lower rostral ACC thickness across all subjects. IL-6 was inversely associated with hippocampal and amygdala volume in healthy subjects only. GPRS for immunometabolic dysregulation were not associated with brain volume or cortical thickness.

CONCLUSIONS

Multiple serum, but not genetic immunometabolic dysregulation markers were found to relate to rostral ACC structure, suggesting that inflammation and metabolic dysregulation may impact the ACC through similar mechanisms.

Neonatal handling enduringly decreases anxiety and stress responses and reduces hippocampus and amygdala volume in a genetic model of differential anxiety: Behavioral-volumetric associations in the Roman rat strains

The hippocampus and amygdala have been proposed as key neural structures related to anxiety. A more active hippocampus/amygdala system has been related to greater anxious responses in situations involving conflict/novelty. The Roman Low- (RLA) and High-avoidance (RHA) rat lines/strains constitute a genetic model of differential anxiety. Relative to RHA rats, RLA rats exhibit enhanced anxiety/fearfulness, augmented hippocampal/amygdala c-Fos expression following exposure to novelty/conflict, increased hippocampal neuronal density and higher endocrine responses to stress. Neonatal handling (NH) is an environmental treatment with long-lasting anxiety/stress-reducing effects in rodents. Since hippocampus and amygdala volume are supposed to be related to anxiety/fear, we hypothesized a greater volume of both areas in RLA than in RHA rats, as well as that NH treatment would reduce anxiety and the volume of both structures, in particular in the RLA strain. Adult untreated and NH-treated RHA and RLA rats were tested for anxiety, sensorimotor gating (PPI), stress-induced corticosterone and prolactin responses, two-way active avoidance acquisition and in vivo 7 T 1H-Magnetic resonance image. As expected, untreated RLA rats showed higher anxiety and post-stress hormone responses, as well as greater hippocampus and amygdala volumes than untreated RHA rats. NH decreased anxiety/stress responses, especially in RLA rats, and significantly reduced hippocampus and amygdala volumes in this strain. Dorsal striatum volume was not different between the strains nor it was affected by NH. Finally, there were positive associations (as shown by correlations, factor analysis and multiple regression) between anxiety and PPI and hippocampus/amygdala volumes.

The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids

Adrenal glucocorticoids are major modulators of multiple functions, including energy metabolism, stress responses, immunity, and cognition. The endogenous secretion of glucocorticoids is normally characterized by a prominent and robust circadian (around 24 hours) oscillation, with a daily peak around the time of the habitual sleep-wake transition and minimal levels in the evening and early part of the night. It has long been recognized that this 24-hour rhythm partly reflects the activity of a master circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus. In the past decade, secondary circadian clocks based on the same molecular machinery as the central master pacemaker were found in other brain areas as well as in most peripheral tissues, including the adrenal glands. Evidence is rapidly accumulating to indicate that misalignment between central and peripheral clocks has a host of adverse effects. The robust rhythm in circulating glucocorticoid levels has been recognized as a major internal synchronizer of the circadian system. The present review examines the scientific foundation of these novel advances and their implications for health and disease prevention and treatment.

Trauma exposure relates to heightened stress, altered amygdala morphology and deficient extinction learning: Implications for psychopathology

Stress exposure causes a structural reorganization in neurons of the amygdala. In particular, animal models have repeatedly shown that both acute and chronic stress induce neuronal hypertrophy and volumetric increase in the lateral and basolateral nuclei of amygdala. These effects are visible on the behavioral level, where stress enhances anxiety behaviors and provokes greater fear learning. We assessed stress and anxiety levels in a group of 18 healthy human trauma-exposed individuals (TR group) compared to 18 non-exposed matched controls (HC group), and related these measurements to amygdala volume. Traumas included unexpected adverse experiences such as vehicle accidents or sudden loss of a loved one. As a measure of aversive learning, we implemented a cued fear conditioning paradigm. Additionally, to provide a biological marker of chronic stress, we measured the sensitivity of the hypothalamus-pituitary-adrenal (HPA) axis using a dexamethasone suppression test. Compared to the HC, the TR group showed significantly higher levels of chronic stress, current stress and trait anxiety, as well as increased volume of the left amygdala. Specifically, we observed a focal enlargement in its lateral portion, in line with previous animal data. Compared to HC, the TR group also showed enhanced late acquisition of conditioned fear and deficient extinction learning, as well as salivary cortisol hypo-suppression to dexamethasone. Left amygdala volumes positively correlated with suppressed morning salivary cortisol. Our results indicate differences in trauma-exposed individuals which resemble those previously reported in animals exposed to stress and in patients with post-traumatic stress disorder and depression. These data provide new insights into the mechanisms through which traumatic stress might prompt vulnerability for psychopathology.

Neuroscience of Childhood Poverty: Evidence of Impacts and Mechanisms as Vehicles of Dialog With Ethics

Several studies have identified associations between poverty and development of self-regulation during childhood, which is broadly defined as those skills involved in cognitive, emotional, and stress self-regulation. These skills are influenced by different individual and contextual factors at multiple levels of analysis (i.e., individual, family, social, and cultural). Available evidence suggests that the influences of those biological, psychosocial, and sociocultural factors on emotional and cognitive development can vary according to the type, number, accumulation of risks, and co-occurrence of adverse circumstances that are related to poverty, the time in which these factors exert their influences, and the individual susceptibility to them. Complementary, during the past three decades, several experimental interventions that were aimed at optimizing development of self-regulation of children who live in poverty have been designed, implemented, and evaluated. Their results suggest that it is possible to optimize different aspects of cognitive performance and that it would be possible to transfer some aspects of these gains to other cognitive domains and academic achievement. We suggest that it is an important task for ethics, notably but not exclusively neuroethics, to engage in this interdisciplinary research domain to contribute analyses of key concepts, arguments, and interpretations. The specific evidence that neuroscience brings to the analyses of poverty and its implications needs to be spelled out in detail and clarified conceptually, notably in terms of causes of and attitudes toward poverty, implications of poverty for brain development, and for the possibilities to reduce and reverse these effects.

Cannabimimetic phytochemicals in the diet - an evolutionary link to food selection and metabolic stress adaptation?

The endocannabinoid system (ECS) is a major lipid signalling network that plays important pro-homeostatic (allostatic) roles not only in the nervous system but also in peripheral organs. There is increasing evidence that there is a dietary component in the modulation of the ECS. Cannabinoid receptors in hominids co-evolved with diet, and the ECS constitutes a feedback loop for food selection and energy metabolism. Here, it is postulated that the mismatch of ancient lipid genes of hunter-gatherers and pastoralists with the high-carbohydrate diet introduced by agriculture could be compensated for via dietary modulation of the ECS. In addition to the fatty acid precursors of endocannabinoids, the potential role of dietary cannabimimetic phytochemicals in agriculturist nutrition is discussed. Dietary secondary metabolites from vegetables and spices able to enhance the activity of cannabinoid-type 2 (CB₂ ) receptors may provide adaptive metabolic advantages and counteract inflammation. In contrast, chronic CB₁ receptor activation in hedonic obese individuals may enhance pathophysiological processes related to hyperlipidaemia, diabetes, hepatorenal inflammation and cardiometabolic risk. Food able to modulate the CB₁ /CB₂ receptor activation ratio may thus play a role in the nutrition transition of Western high-calorie diets. In this review, the interplay between diet and the ECS is highlighted from an evolutionary perspective. The emerging potential of cannabimimetic food as a nutraceutical strategy is critically discussed.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Enduring, Sexually Dimorphic Impact of In Utero Exposure to Elevated Levels of Glucocorticoids on Midbrain Dopaminergic Populations

Glucocorticoid hormones (GCs) released from the fetal/maternal glands during late gestation are required for normal development of mammalian organs and tissues. Accordingly, synthetic glucocorticoids have proven to be invaluable in perinatal medicine where they are widely used to accelerate fetal lung maturation when there is risk of pre-term birth and to promote infant survival. However, clinical and pre-clinical studies have demonstrated that inappropriate exposure of the developing brain to elevated levels of GCs, either as a result of clinical over-use or after stress-induced activation of the fetal/maternal adrenal cortex, is linked with significant effects on brain structure, neurological function and behaviour in later life. In order to understand the underlying neural processes, particular interest has focused on the midbrain dopaminergic systems, which are critical regulators of normal adaptive behaviours, cognitive and sensorimotor functions. Specifically, using a rodent model of GC exposure in late gestation (approximating human brain development at late second/early third trimester), we demonstrated enduring effects on the shape and volume of the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) (origins of the mesocorticolimbic and nigrostriatal dopaminergic pathways) on the topographical organisation and size of the dopaminergic neuronal populations and astrocytes within these nuclei and on target innervation density and neurochemical markers of dopaminergic transmission (receptors, transporters, basal and amphetamine-stimulated dopamine release at striatal and prefrontal cortical sites) that impact on the adult brain. The effects of antenatal GC treatment (AGT) were both profound and sexually-dimorphic, not only in terms of quantitative change but also qualitatively, with several parameters affected in the opposite direction in males and females. Although such substantial neurobiological changes might presage marked behavioural effects, in utero GC exposure had only a modest or no effect, depending on sex, on a range of conditioned and unconditioned behaviours known to depend on midbrain dopaminergic transmission. Collectively, these findings suggest that apparent behavioural normality in certain tests, but not others, arises from AGT-induced adaptations or compensatory mechanisms within the midbrain dopaminergic systems, which preserve some, but not all functions. Furthermore, the capacities for molecular adaptations to early environmental challenge are different, even opponent, in males and females, which may account for their differential resilience or failure to perform adequately in behavioural tests. Behavioural "normality" is thus achieved by the midbrain dopaminergic network operating outside its normal limits (in a state of allostasis), rendering it at greater risk to malfunction when challenged in later life. Sex-specific neurobiological programming of midbrain dopaminergic systems may, therefore, have psychopathological relevance for the sex bias commonly found in brain disorders associated with these systems, and which have a neurodevelopmental component, including schizophrenia, ADHD (attention/deficit hyperactivity disorders), autism, depression and substance abuse.

Serum Response Factor (SRF) Ablation Interferes with Acute Stress-Associated Immediate and Long-Term Coping Mechanisms

Stress experience modulates behavior, metabolism, and energy expenditure of organisms. One molecular hallmark of an acute stress response is a rapid induction of immediate early genes (IEGs) such as c-Fos and Egr family members. IEG transcription in neurons is mediated by the neuronal activity-driven gene regulator serum response factor (SRF). We show a first role of SRF in immediate and long-lasting acute restraint stress (AS) responses. For this, we employed a standardized mouse phenotyping protocol at the German Mouse Clinic (GMC) including behavioral, metabolic, and cardiologic tests as well as gene expression profiling to analyze the consequences of forebrain-specific SRF deletion in mice exposed to AS. Adult mice with an SRF deletion in glutamatergic neurons (Srf; ^{CaMKIIa-CreERT2} ) showed hyperactivity, decreased anxiety, and impaired working memory. In response to restraint AS, instant stress reactivity including locomotor behavior and corticosterone induction was impaired in Srf mutant mice. Interestingly, even several weeks after previous AS exposure, SRF-deficient mice showed long-lasting AS-associated changes including altered locomotion, metabolism, energy expenditure, and cardiovascular changes. This suggests a requirement of SRF for mediating long-term stress coping mechanisms in wild-type mice. SRF ablation decreased AS-mediated IEG induction and activity of the actin severing protein cofilin. In summary, our data suggest an SRF function in immediate AS reactions and long-term post-stress-associated coping mechanisms.

Differences in frontal and limbic brain activation in a small sample of monozygotic twin pairs discordant for severe stressful life events

Monozygotic twin pairs provide a valuable opportunity to control for genetic and shared environmental influences while studying the effects of nonshared environmental influences. The question we address with this design is whether monozygotic twins selected for discordance in exposure to severe stressful life events during development (before age 18) demonstrate differences in brain activation during performance of an emotional word-face Stroop task. In this study, functional magnetic resonance imaging was used to assess brain activation in eighteen young adult twins who were discordant in exposure to severe stress such that one twin had two or more severe events compared to their control co-twin who had no severe events. Twins who experienced higher levels of stress during development, compared to their control co-twins with lower stress, exhibited significant clusters of greater activation in the ventrolateral and medial prefrontal cortex, basal ganglia, and limbic regions. The control co-twins showed only the more typical recruitment of frontoparietal regions thought to be important for executive control of attention and maintenance of task goals. Behavioral performance was not significantly different between twins within pairs, suggesting the twins with stress recruited additional neural resources associated with affective processing and updating working memory when performing at the same level. This study provides a powerful glimpse at the potential effects of stress during development while accounting for shared genetic and environmental influences.