Stress and anxiety: structural plasticity and epigenetic regulation as a consequence of stress

Hypothalamic CNTF volume transmission shapes cortical noradrenergic excitability upon acute stress

Stress-induced cortical alertness is maintained by a heightened excitability of noradrenergic neurons innervating, notably, the prefrontal cortex. However, neither the signaling axis linking hypothalamic activation to delayed and lasting noradrenergic excitability nor the molecular cascade gating noradrenaline synthesis is defined. Here, we show that hypothalamic corticotropin-releasing hormone-releasing neurons innervate ependymal cells of the 3rd ventricle to induce ciliary neurotrophic factor (CNTF) release for transport through the brain's aqueductal system. CNTF binding to its cognate receptors on norepinephrinergic neurons in the locus coeruleus then initiates sequential phosphorylation of extracellular signal-regulated kinase 1 and tyrosine hydroxylase with the Ca2+-sensor secretagogin ensuring activity dependence in both rodent and human brains. Both CNTF and secretagogin ablation occlude stress-induced cortical norepinephrine synthesis, ensuing neuronal excitation and behavioral stereotypes. Cumulatively, we identify a multimodal pathway that is rate-limited by CNTF volume transmission and poised to directly convert hypothalamic activation into long-lasting cortical excitability following acute stress.

Leptin in depression: a potential therapeutic target

Leptin, produced and secreted by white adipose tissue, plays a critical role in regulating body weight, food intake, and energy metabolism. Recently, several studies have identified an underlying role for leptin in regulation of mood and cognition via regulation of synaptic changes in the brain that have been associated with antidepressant-like actions. Brain neural plasticity occurs in response to a range of intrinsic and extrinsic stimuli, including those that may mediate the effects of antidepressants. Neural plasticity theories of depression are thought to explain multiple aspects of depression and the effects of antidepressants. It is also well documented that leptin has effects on neural plasticity. This review summarizes the recent literature on the role of leptin in neural plasticity in order to elaborate the possible mechanism of leptin’s antidepressant-like effects. Recent findings provide new insights into the underlying mechanisms of neural plasticity in depression. Leptin may influence these mechanisms and consequently constitute a possible target for novel therapeutic approaches to the treatment of depression.

Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity

Contemplative practices, such as meditation and yoga, are increasingly popular among the general public and as topics of research. Beneficial effects associated with these practices have been found on physical health, mental health and cognitive performance. However, studies and theories that clarify the underlying mechanisms are lacking or scarce. This theoretical review aims to address and compensate this scarcity. We will show that various contemplative activities have in common that breathing is regulated or attentively guided. This respiratory discipline in turn could parsimoniously explain the physical and mental benefits of contemplative activities through changes in autonomic balance. We propose a neurophysiological model that explains how these specific respiration styles could operate, by phasically and tonically stimulating the vagal nerve: respiratory vagal nerve stimulation (rVNS). The vagal nerve, as a proponent of the parasympathetic nervous system (PNS), is the prime candidate in explaining the effects of contemplative practices on health, mental health and cognition. We will discuss implications and limitations of our model.

Vulnerability and resilience to Alzheimer's disease: early life conditions modulate neuropathology and determine cognitive reserve

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with a high prevalence among the elderly and a huge personal and societal impact. Recent epidemiological studies have indicated that the incidence and age of onset of sporadic AD can be modified by lifestyle factors such as education, exercise, and (early) stress exposure. Early life adversity is known to promote cognitive decline at a later age and to accelerate aging, which are both primary risk factors for AD. In rodent models, exposure to 'negative' or 'positive' early life experiences was recently found to modulate various measures of AD neuropathology, such as amyloid-beta levels and cognition at later ages. Although there is emerging interest in understanding whether experiences during early postnatal life also modulate AD risk in humans, the mechanisms and possible substrates underlying these long-lasting effects remain elusive.

METHODS

We review literature and discuss the role of early life experiences in determining later age and AD-related processes from a brain and cognitive 'reserve' perspective. We focus on rodent studies and the identification of possible early determinants of later AD vulnerability or resilience in relation to early life adversity/enrichment.

RESULTS

Potential substrates and mediators of early life experiences that may influence the development of AD pathology and cognitive decline are: programming of the hypothalamic-pituitary-adrenal axis, priming of the neuroinflammatory response, dendritic and synaptic complexity and function, overall brain plasticity, and proteins such as early growth response protein 1 (EGR1), activity regulated cytoskeleton-associated protein (Arc), and repressor element-1 silencing transcription factor (REST).

CONCLUSIONS

We conclude from these rodent studies that the early postnatal period is an important and sensitive phase that influences the vulnerability to develop AD pathology. Yet translational studies are required to investigate whether early life experiences also modify AD development in human studies, and whether similar molecular mediators can be identified in the sensitivity to develop AD in humans.

Role of inflammation in epilepsy and neurobehavioral comorbidities: Implication for therapy

Epilepsy is a devastating condition affecting around 70 million people worldwide. Moreover, the quality of life of people with epilepsy (PWE) is worsened by a series of comorbidities. The neurobehavioral comorbidities discussed herein share a reciprocal and complex relationship with epilepsy, which ultimately complicates the treatment process in PWE. Understanding the mechanistic pathway by which these comorbidities are associated with epilepsy might be instrumental in developing therapeutic interventions. Inflammatory cytokine signaling in the brain regulates important brain functions including neurotransmitter metabolism, neuroendocrine function, synaptic plasticity, dopaminergic transmission, the kynurenine pathway, and affects neurogenesis as well as the neural circuitry of moods. In this review, we hypothesize that the complex relationship between epilepsy and its related comorbidities (cognitive impairment, depression, anxiety, autism, and schizophrenia) can be unraveled through the inflammatory mechanism that plays a prominent role in all these individual conditions. An ample amount of evidence is available reporting the role of inflammation in epilepsy and all individual comorbid condition but their complex relationship with epilepsy has not yet been explored through the prospective of inflammatory pathway. Our review suggests that epilepsy and its neurobehavioral comorbidities are associated with elevated levels of several key inflammatory markers. This review also sheds light on the mechanistic association between epilepsy and its neurobehavioral comorbidities. Moreover, we analyzed several anti-inflammatory therapies available for epilepsy and its neurobehavioral comorbidities. We suggest, these anti-inflammatory therapies might be a possible intervention and could be a promising strategy for preventing epileptogenesis and its related neurobehavioral comorbidities.

Some Metatheoretical Principles for Personality Neuroscience

Theories in personality neuroscience must aim to be consistent with several levels of explanation. If we view personality traits as constructs located only at the psychological level, we must still make their explanations compatible with observations and theories at lower levels, particularly with what we know at the neural level. If we view personality traits as constructs located only at the neural level, we will still need to predict their emergent effects at the psychological level. Personality theory at present treats traits as psychological-level constructs, with even the recent neurally oriented Cybernetic Big Five Theory specified in terms of a "conceptual nervous system" and not requiring complete or immediate translation into neural mechanisms. Here, we argue for the existence of phylogenetically old, neural-level traits that are substantially conserved across many vertebrate species. We first ask what known mechanisms control trait-like properties of neural systems: Focusing on hormones, the GABAA receptor, and amine neurotransmitter systems. We derive from what we know about these sources of neuronal modulation some metatheoretical principles to guide the future development of those aspects of personality theory, starting with neural-level trait constructs and drawing implications for higher-level trait psychology observations. Current descriptive approaches such as the Big Five are an essential precursor to personality neuroscience, but may not map one-to-one to the mechanisms and constructs of a neuroscience-based approach to traits.

Profiling changes in cortical astroglial cells following chronic stress

Recent studies have suggested that cortical astroglia play an important role in depressive-like behaviors. Potential astroglial contributions have been proposed based on their known neuroplastic functions, such as glutamate recycling and synaptic plasticity. However, the specific mechanisms by which astroglial cells may contribute or protect against a depressive phenotype remain unknown. To delineate astroglial changes that accompany depressive-like behavior, we used astroglial-specific bacTRAP mice exposed to chronic variable stress (CVS) and profiled the astroglial translatome using translating ribosome affinity purification (TRAP) in conjunction with RNAseq. As expected, CVS significantly increased anxiety- and depressive-like behaviors and corticosterone levels and decreased GFAP expression in astroglia, although this did not reflect a change in the total number of astroglial cells. TRAPseq results showed that CVS decreased genes associated with astroglial plasticity: RhoGTPases, growth factor signaling, and transcription regulation, and increased genes associated with the formation of extracellular matrices such as perineuronal nets (PNNs). PNNs inhibit neuroplasticity and astroglia contribute to the formation, organization, and maintenance of PNNs. To validate our TRAPseq findings, we showed an increase in PNNs following CVS. Degradation of PNNs in the prefrontal cortex of mice exposed to CVS reversed the CVS-induced behavioral phenotype in the forced swim test. These data lend further support to the neuroplasticity hypothesis of depressive behaviors and, in particular, extend this hypothesis beyond neuronal plasticity to include an overall decrease in genes associated with cortical astroglial plasticity following CVS. Further studies will be needed to assess the antidepressant potential of directly targeting astroglial cell function in models of depression.

Novel antidepressant effects of Paeonol alleviate neuronal injury with concomitant alterations in BDNF, Rac1 and RhoA levels in chronic unpredictable mild stress rats

RATIONALE

Increasing evidence has suggested that major depressive disorder (MDD) is highly associated with brain-derived neurotrophic factor (BDNF) levels, dendrites atrophy, and loss of dendritic spines, especially in emotion-associated brain regions including the hippocampus. Paeonol is a kind of polyphenols natural product with a variety of therapeutic effects. Recent studies have reported its antidepressant effects. However, it is unclear what signaling pathways contribute to improve MDD.

OBJECTIVE

The present study investigated the effect of Paeonol on hippocampal neuronal morphology and its possible signaling pathways in chronic unpredictable mild stress (CUMS) rat model.

METHODS

Using CUMS rat model, the antidepressant-like effect of Paeonol was validated via depression-related behavioral tests. Neuronal morphology in hippocampal CA1 and DG was assessed using ImageJ's Sholl plugin and RESCONSTRUCT software. BDNF signaling pathway-related molecules was determined by Western blotting.

RESULTS

Paeonol attenuated CUMS-induced depression-like behaviors, which were accompanied by hippocampal neuronal morphological alterations. After Paeonol treatment for 4 weeks, the dendritic length and complexity and the density of dendritic spines markedly increased in the hippocampal CA1 and the dentate gyrus (DG). However, CUMS or Paeonol treatment does not selectively affect dendritic spine types. Simultaneously, administration of Paeonol deterred CUMS-induced cofilin1 activation that is essential for remolding of dendritic spines. The induction of CUMS downregulated BDNF levels and upregulated Rac1/RhoA levels; however, the tendency of these was inhibited by treatment with Paeonol.

CONCLUSION

Our data suggest that BDNF-Rac1/RhoA pathway may be involved in attenuation of CUMS-induced behavioral and neuronal damage by Paeonol that may represent a novel therapeutic agent for depression.

Impact of video games on plasticity of the hippocampus

The hippocampus is critical to healthy cognition, yet results in the current study show that action video game players have reduced grey matter within the hippocampus. A subsequent randomised longitudinal training experiment demonstrated that first-person shooting games reduce grey matter within the hippocampus in participants using non-spatial memory strategies. Conversely, participants who use hippocampus-dependent spatial strategies showed increased grey matter in the hippocampus after training. A control group that trained on 3D-platform games displayed growth in either the hippocampus or the functionally connected entorhinal cortex. A third study replicated the effect of action video game training on grey matter in the hippocampus. These results show that video games can be beneficial or detrimental to the hippocampal system depending on the navigation strategy that a person employs and the genre of the game.

Is the Association of ADHD with Socio-Economic Disadvantage Explained by Child Comorbid Externalizing Problems or Parent ADHD?

It has been unclear whether an associations of child ADHD with socio-economic disadvantage (SES) could be accounted for by (a) parental ADHD explaining both low SES and child ADHD, and/or (b) the joint overlap of ODD or CD with low SES and ADHD. Study 1 used a community-recruited case-control sample with detailed evaluation of SES indicators, child ADHD, child externalizing, and parent ADHD symptoms (n = 931 children, 521 ADHD, 577 boys, 354 girls) in a path modeling analysis with latent variables. Study 2 evaluated ADHD and externalizing behavior in a regression model using a poverty index for SES, in 70,927 children (48.2% female) aged 5-17 years from the US 2011-2012 National Survey of Children's Health (NSCH). In Study 1, lower SES was related to the ADHD latent variable, β = -.18, p < .001; 95%CI [-.25,-.12]. This effect held when parent ADHD and child ODD and CD were in the model, β = -.11, p < .01, 95% CI [-.09,-.03], equivalent to OR = 1.50, 95% CI[1.12-2.04]). In Study 2, these results replicated. Adjusting only for age and sex, children from families who were below 200% of the federal poverty line were more likely to have moderate or severe ADHD than no ADHD, versus children above that line, OR = 2.13, 95% CI[1.79,2.54], p < .001. The effect held after adjusting for disruptive/externalizing problems, OR = 1.61, p < .01, 95%CI [1.32,1.96]. The effect size for comparable models was similar across both studies, lending higher confidence to the results. It is concluded that the SES association with child ADHD is not explained by artifact and requires a mechanistic explanation.

[A role of progesterone and its metabolites in regulation functions of the brain]

The review presents literature data reflecting the nature and mechanism of the effect of progesterone and its metabolites on human and animal brain structures. Particular attention is paid to neuroprotective, anticonvulsant, anti-anxiety and sedative properties of this hormone, which determines the prospect of its use for the prevention and treatment of human neurodegenerative diseases, epilepsy, sleep disorders, and anxiety-depressive spectrum disorders, including premenstrual and climacteric syndromes.

Genes and Aggressive Behavior: Epigenetic Mechanisms Underlying Individual Susceptibility to Aversive Environments

Over the last two decades, the study of the relationship between nature and nurture in shaping human behavior has encountered a renewed interest. Behavioral genetics showed that distinct polymorphisms of genes that code for proteins that control neurotransmitter metabolic and synaptic function are associated with individual vulnerability to aversive experiences, such as stressful and traumatic life events, and may result in an increased risk of developing psychopathologies associated with violence. On the other hand, recent studies indicate that experiencing aversive events modulates gene expression by introducing stable changes to DNA without modifying its sequence, a mechanism known as “epigenetics”. For example, experiencing adversities during periods of maximal sensitivity to the environment, such as prenatal life, infancy and early adolescence, may introduce lasting epigenetic marks in genes that affect maturational processes in brain, thus favoring the emergence of dysfunctional behaviors, including exaggerate aggression in adulthood. The present review discusses data from recent research, both in humans and animals, concerning the epigenetic regulation of four genes belonging to the neuroendocrine, serotonergic and oxytocinergic pathways—Nuclear receptor subfamily 3-group C-member 1 (NR3C1), oxytocin receptor (OXTR), solute carrier-family 6 member 4 (SLC6A4) and monoamine oxidase A (MAOA)—and their role in modulating vulnerability to proactive and reactive aggressive behavior. Behavioral genetics and epigenetics are shedding a new light on the fine interaction between genes and environment, by providing a novel tool to understand the molecular events that underlie aggression. Overall, the findings from these studies carry important implications not only for neuroscience, but also for social sciences, including ethics, philosophy and law.

Acute Stress-Induced Epigenetic Modulations and Their Potential Protective Role Toward Depression

Psychiatric disorders entail maladaptive processes impairing individuals’ ability to appropriately interface with environment. Among them, depression is characterized by diverse debilitating symptoms including hopelessness and anhedonia, dramatically impacting the propensity to live a social and active life and seriously affecting working capability. Relevantly, besides genetic predisposition, foremost risk factors are stress-related, such as experiencing chronic psychosocial stress—including bullying, mobbing and abuse—, and undergoing economic crisis or chronic illnesses. In the last few years the field of epigenetics promised to understand core mechanisms of gene-environment crosstalk, contributing to get into pathogenic processes of many disorders highly influenced by stressful life conditions. However, still very little is known about mechanisms that tune gene expression to adapt to the external milieu. In this Perspective article, we discuss a set of protective, functionally convergent epigenetic processes induced by acute stress in the rodent hippocampus and devoted to the negative modulation of stress-induced immediate early genes (IEGs) transcription, hindering stress-driven morphostructural modifications of corticolimbic circuitry. We also suggest that chronic stress damaging protective epigenetic mechanisms, could bias the functional trajectory of stress-induced neuronal morphostructural modification from adaptive to maladaptive, contributing to the onset of depression in vulnerable individuals. A better understanding of the epigenetic response to stress will be pivotal to new avenues of therapeutic intervention to treat depression, especially in light of limited efficacy of available antidepressant drugs.

Ketamine and rapid-acting antidepressants: a new era in the battle against depression and suicide

Therapeutic medications for the treatment of depression have serious limitations, particularly delayed onset and low rates of efficacy. However, the discovery that a single subanesthetic dose of ketamine, a glutamate NMDA receptor channel blocker, can produce a rapid (within hours) antidepressant response that is sustained (about 1 week), even in patients considered treatment-resistant, has invigorated the field. In addition to these remarkable actions, ketamine has proven effective for the treatment of suicidal ideation. Efforts are under way to develop ketamine-like drugs with fewer side effects as well as agents that act at other sites within the glutamate neurotransmitter system. This includes ketamine metabolites and stereoisomers, drugs that act as NMDA allosteric modulators or that block mGluR2/3 autoreceptors. In addition, targets that enhance glutamate neurotransmission or synaptic function (or both), which are essential for the rapid and sustained antidepressant actions of ketamine in rodent models, are being investigated; examples are the muscarinic cholinergic antagonist scopolamine and activators of mechanistic target of rapamycin complex 1 (mTORC1) signaling, which is required for the actions of ketamine. The discovery of ketamine and its unique mechanisms heralds a new era with tremendous promise for the development of novel, rapid, and efficacious antidepressant medications.

Antidepressant-like effects of embelin and its possible mechanisms of action in chronic unpredictable stress-induced mice

Objectives Embelin, a principal active constituent of embelin ribes burm, has good therapeutic effects on various diseases. To explore the effects and underlying mechanisms of embelin on depression, we made a preliminary study to clarify this issue. Methods We first used chronic unpredictable stress (CUS) to construct the model of depression in mice. Then, we determined the effects of embelin on CUS-induced behavioral dysfunction using open field test, sucrose preference test, tail suspension test and forced swimming test. Furthermore, we used the biological experiments to evaluate the changes of brain-derived neurotrophic factor (BDNF), oxidative stress, neuronal inflammation and the hypothalamic pituitary adrenal (HPA) axis after embelin treatment. Results The behavioral tests indicated embelin indeed had efficient antidepressant effects. Moreover, enhanced BDNF expression, decreased oxidative stress markers (TBARS, nitric oxide) activities, elevated antioxidants (total thiol, catalase) expression, decreased pro-inflammatory cytokines (IL-6, TNF-α, IL-1β and COX-2) expression and normalized the HPA axis activity were found after embelin treatment in CUS-induced mice. Hence, the results of biological experiments confirmed the antidepressant-like effects of embelin. Discussion These results indicated that embelin can effectively suppress CUS-induced depressive-like behaviors through increasing BDNF expression, preventing brain from oxidative stress and neuronal inflammation, and normalizing the HPA activity.

Brain region-specific expression of genes mapped within quantitative trait loci for behavioral responsiveness to acute stress in Fisher 344 and Wistar Kyoto male rats

Acute stress responsiveness is a quantitative trait that varies in severity from one individual to another; however, the genetic component underlying the individual variation is largely unknown. Fischer 344 (F344) and Wistar Kyoto (WKY) rat strains show large differences in behavioral responsiveness to acute stress, such as freezing behavior in response to footshock during the conditioning phase of contextual fear conditioning (CFC). Quantitative trait loci (QTL) have been identified for behavioral responsiveness to acute stress in the defensive burying (DB) and open field test (OFT) from a reciprocal F2 cross of F344 and WKY rat strains. These included a significant QTL on chromosome 6 (Stresp10). Here, we hypothesized that the Stresp10 region harbors genes with sequence variation(s) that contribute to differences in multiple behavioral response phenotypes between the F344 and WKY rat strains. To test this hypothesis, first we identified differentially expressed genes within the Stresp10 QTL in the hippocampus, amygdala, and frontal cortex of F344 and WKY male rats using genome-wide microarray analyses. Genes with both expression differences and non-synonymous sequence variations in their coding regions were considered candidate quantitative trait genes (QTGs). As a proof-of-concept, the F344.WKY-Stresp10 congenic strain was generated with the Stresp10 WKY donor region into the F344 recipient strain. This congenic strain showed behavioral phenotypes similar to those of WKYs. Expression patterns of Gpatch11 (G-patch domain containing 11), Cdkl4 (Cyclin dependent kinase like 4), and Drc1 (Dynein regulatory complex subunit 1) paralleled that of WKY in the F344.WKY-Stresp10 strain matching the behavioral profiles of WKY as opposed to F344 parental strains. We propose that these genes are candidate QTGs for behavioral responsiveness to acute stress.

Secondary traumatic stress increases expression of proteins implicated in peripheral and central sensitization of trigeminal neurons

The pathology of migraine, a common neurological disease, involves sensitization and activation of trigeminal nociceptive neurons to promote hyperalgesia and allodynia during an attack. Migraineurs often exhibit characteristics of a hyperexcitable or hypervigilant nervous system. One of the primary reported risk factors for development of a hyperexcitable trigeminal system is chronic, unmanaged stress and anxiety. While primary traumatic stress is a commonly cited risk factor for many pain conditions, exposure to secondary traumatic stress early in life is also thought to be a contributing risk factor. The goal of this study was to investigate cellular changes within the spinal trigeminal nucleus and trigeminal ganglion mediated by secondary traumatic stress. Male Sprague Dawley rats (sender) were subjected to forced swim testing (primary traumatic stress) and were then housed in close visual, olfactory, and auditory proximity to the breeding male and female rats, pregnant female rats, or female rats and their nursing offspring (all receivers). In response to secondary stress, levels of calcitonin gene-related peptide, active forms of the mitogen activated protein kinases ERK, JNK, and p38, and astrocyte expression of glial fibrillary acidic protein were significantly elevated in the spinal trigeminal nucleus in day 45 offspring when compared to naïve offspring. In addition, increased nuclear expression of ERK and p38 was observed in trigeminal ganglion neurons. Our results demonstrate that secondary traumatic stress promotes cellular events associated with prolonged trigeminal sensitization in the offspring, and provides a mechanism of how early life stress may function as a risk factor for migraine.

The Hippocampus is a Critical Site Mediating Antidepressant-like Activity of Apelin-13 in Rats

The peptide apelin and its receptor APJ are found to express in multiple brain regions, especially in the regions such as the hippocampus and hypothalamus that play important roles in stress and depression. The distribution of apelin and APJ suggests that the apelinergic signaling may be a key mediator in the development of stress-related depressive behavior. We recently demonstrated that intracerebroventricular (i.c.v) injection of apelin-13 exerts an antidepressant-like activity in the rat forced swimming test (FST). However, the possible brain region mediating apelin-13's antidepressant-like activity remains unclear. In the present study, we determined whether the hippocampus and hypothalamus are the possible regions mediating antidepressant-like activity of apelin-13. We found that forced swimming exposure upregulated apelin and APJ protein expression levels in the hippocampus but not hypothalamus in rats. Further, intrahippocampal injection of apelin-13 exerted an antidepressant-like activity (as indicated by a decreased immobility behavior), and intrahippocampal infusion of APJ receptor antagonist F13A blocked the antidepressant-like activity produced by i.c.v injection of apelin-13 in the FST. Moreover, intrahypothalamic injection of apelin-13 did not affect the immobility behavior in the FST. These findings suggest that the hippocampus, but not hypothalamus, is a critical site mediating antidepressant-like activity of apelin-13 in rats.

Studies into the anxiolytic actions of agomelatine in social isolation reared rats: Role of corticosterone and sex

Anxiety disorders are severely disabling, while current pharmacological treatments are complicated by delayed onset, low remission rates and side-effects. Sex is also noted to contribute towards illness severity and treatment response. Agomelatine is a melatonin (MT₁/MT₂) agonist and serotonin (5-HT_2C) antagonist purported to be anxiolytic in clinical and some pre-clinical studies. We undertook a detailed analysis of agomelatine's anxiolytic activity in a neurodevelopmental model of anxiety, the social isolation reared rat. Rats received sub-chronic treatment with vehicle or agomelatine (40 mg/kg per day intraperitoneally at 16:00 h for 16 days), with behaviour analysed in the open field test, social interaction test and elevated plus maze. The contribution of corticosterone and sex was also studied. Social isolation rearing increased locomotor activity and reduced social interaction in the social interaction test, and was anxiogenic in the elevated plus maze in males and females. Agomelatine reversed these behaviours. Male and female social isolation reared rats developed anxiety-like behaviours to a similar degree, although response to agomelatine was superior in male rats. Social isolation rearing decreased plasma corticosterone in both sexes and tended to higher levels in females, although agomelatine did not affect corticosterone in either sex. Concluding, agomelatine is anxiolytic in SIR rats, although correcting altered corticosterone could not be implicated. Sex-related differences in the response to agomelatine are evident.

Severely impaired adult brain neurogenesis in cyclin D2 knock-out mice produces very limited phenotypic changes

The discovery of new neurons being produced in the brains of adult mammals (adult brain neurogenesis) began a quest to determine the function(s) of these cells. Major hypotheses in the field have assumed that these neurons play pivotal role, in particular, in learning and memory phenomena, mood control, and epileptogenesis. In our studies summarized herein, we used cyclin D2 knockout (KO) mice, as we have shown that cyclin D2 is the key factor in adult brain neurogenesis and thus its lack produces profound impairment of the process. On the other hand, developmental neurogenesis responsible for the brain formation depends only slightly on cyclin D2, as the mutants display minor structural abnormalities, such as smaller hippocampus and more severe disturbances in the structure of the olfactory bulbs. Surprisingly, the studies have revealed that cyclin D2 KO mice did not show major deficits in several behavioral paradigms assessing hippocampal learning and memory. Furthermore, missing adult brain neurogenesis affected neither action of antidepressants, nor epileptogenesis. On the other hand, minor deficits observed in cyclin D2 KO mice in fine tuning of cognitive functions, species-typical behaviors and alcohol consumption might be explained by a reduced hippocampal size and/or other developmentally driven brain impairments observed in these mutant mice. In aggregate, surprisingly, missing almost entirely adult brain neurogenesis produces only very limited behavioral phenotype that could be attributed to the consequences of the development-dependent minor brain abnormalities.

How does early maternal separation and chronic stress in adult rats affect the immunoreactivity of serotonergic neurons within the dorsal raphe nucleus?

Vulnerability to emotional disorders like depression derives from interactions between early and late environments, including stressful conditions. The serotonin (5HT) system is strongly affected by stress and chronic unpredictable stress can alter the 5HT system. We evaluated the distribution of active serotonergic neurons in the dorsal raphe nucleus (DR) through immunohistochemistry in maternally separated and chronically stressed rats treated with an antidepressant, tianeptine, whose mechanism of action is still under review. Male Wistar rats were subjected to daily maternal separation (MS) for 4.5 h between postnatal days (PND) 1-21, or to animal facility rearing (AFR). Between (PND) days 50-74, rats were exposed to chronic unpredictable stress and were treated daily with tianeptine (10 mg/kg) or vehicle. We found an interaction between the effects of MS and chronic unpredictable stress on Fos-5HT immunoreactive cells at mid-caudal level of the DR. MS-chronically stressed rats showed an increase of Fos-5HT immunoreactive cells compared with AFR-chronically stressed rats. The ventrolateral (DRL/VLPAG) and dorsal (DRD) subdivisions of the DR were significantly more active than the ventral part (DRV). At the rostral level of the DR, tianeptine decreased the number of Fos-5HT cells in DR in the AFR groups, both unstressed and stressed. Overall, our results support the idea of a match in phenotype exhibited when the early and the adult environment correspond.

Engaging homeostatic plasticity to treat depression

Major depressive disorder (MDD) is a complex and heterogeneous mood disorder, making it difficult to develop a generalized, pharmacological therapy that is effective for all who suffer from MDD. Through the fortuitous discovery of N-methyl-D-aspartate receptor (NMDAR) antagonists as effective antidepressants, we have gained key insights into how antidepressant effects can be produced at the circuit and molecular levels. NMDAR antagonists act as rapid-acting antidepressants such that relief from depressive symptoms occurs within hours of a single injection. The mode of action of NMDAR antagonists seemingly relies on their ability to activate protein-synthesis-dependent homeostatic mechanisms that restore top-down excitatory connections. Recent evidence suggests that NMDAR antagonists relieve depressive symptoms by forming new synapses resulting in increased excitatory drive. This event requires the mammalian target of rapamycin complex 1 (mTORC1), a signaling pathway that regulates synaptic protein synthesis. Herein, we review critical studies that shed light on the action of NMDAR antagonists as rapid-acting antidepressants and how they engage a neuron's or neural network's homeostatic mechanisms to self-correct. Recent studies notably demonstrate that a shift in γ-amino-butyric acid receptor B (GABA_BR) function, from inhibitory to excitatory, is required for mTORC1-dependent translation with NMDAR antagonists. Finally, we discuss how GABA_BR activation of mTORC1 helps resolve key discrepancies between rapid-acting antidepressants and local homeostatic mechanisms.

A translational approach to the genetics of anxiety disorders

There have been important advances in our understanding of the genetic architecture of anxiety disorders. At the same time, relatively few genes have reached genome wide significance in anxiety disorders, and there is relatively little work on how exposure to an adverse environment impacts on gene expression in either animal models or human clinical populations. Here we assessed differential expression of genes of the dorsal striatum involved in synaptic transmission in an animal models of early adversity (maternal separation followed by restraint stress), and investigated whether variants in these genes were associated with risk for anxiety disorders, particularly in the presence of environmental stressors. Fifty-two male Sprague Dawley rats underwent maternal separation, and gene expression was studied using array technology. The human homologues of the differentially expressed genes were screened and analysed in a DSM-IV anxiety disorders cohort, and healthy controls (patients, n = 92; controls, n = 194), using blood. Two candidate genes (Mmp9 and Bdnf) were aberrantly expressed in the experimental rodent group relative to controls. Four single nucleotide polymorphisms (SNPs) in the human homologues of these genes were significantly associated with susceptibility for anxiety disorders (MMP9: rs3918242 and BDNF: rs6265, rs10835210 and rs11030107). Three of these (BDNF: rs6265, rs10835210, rs11030107) were found to interact significantly with childhood trauma severity resulting in increased likelihood of an anxiety disorder diagnosis. This study provides insights into the utility of rat models for identifying molecular candidates for anxiety disorders in humans.

Stress system dysregulation in pediatric generalized anxiety disorder associated with comorbid depression

Because chronic stress is an important risk factor for anxiety states and depressive disorders, we studied hypothalamus-pituitary-adrenal (HPA) axis and sympathetic system activity via changes in cortisol and alpha amylase activity levels in pediatric generalized anxiety disorder (GAD) patients (n = 26) with comorbid depression and a healthy comparison group (n = 26). Morning plasma cortisol and diurnal profiles of salivary cortisol and salivary alpha amylase (sAA) activity were assessed, also reactivity of HPA-axis, sAA activity, and heart rate following a psychosocial stressor (Trier Social Stress Test for children). GAD patients with comorbid depression showed increased morning plasma and salivary cortisol levels, ameliorating throughout in-patient treatment, and higher sAA activity in their diurnal profile. Both HPA and sympathetic activity positively correlated with the severity of anxiety and depression. We also demonstrated a blunted HPA and sympathetic response to acute stress in patients. This pattern of neuroendocrine and sympathetic changes seems to be distinct from the one previously reported in pediatric patients with only social anxiety or depressive disorders. We propose morning plasma and saliva cortisol levels as potential physiological indicators for supporting the evaluation of symptoms' severity and treatment progress in children with GAD and comorbid depressive disorder.

Neural Plasticity Is Involved in Physiological Sleep, Depressive Sleep Disturbances, and Antidepressant Treatments

Depression, which is characterized by a pervasive and persistent low mood and anhedonia, greatly impacts patients, their families, and society. The associated and recurring sleep disturbances further reduce patient's quality of life. However, therapeutic sleep deprivation has been regarded as a rapid and robust antidepressant treatment for several decades, which suggests a complicated role of sleep in development of depression. Changes in neural plasticity are observed during physiological sleep, therapeutic sleep deprivation, and depression. This correlation might help us to understand better the mechanism underlying development of depression and the role of sleep. In this review, we first introduce the structure of sleep and the facilitated neural plasticity caused by physiological sleep. Then, we introduce sleep disturbances and changes in plasticity in patients with depression. Finally, the effects and mechanisms of antidepressants and therapeutic sleep deprivation on neural plasticity are discussed.

Enhanced ventral hippocampal synaptic transmission and impaired synaptic plasticity in a rodent model of alcohol addiction vulnerability

It has long been appreciated that adolescence represents a uniquely vulnerable period when chronic exposure to stressors can precipitate the onset of a broad spectrum of psychiatric disorders and addiction in adulthood. However, the neurobiological substrates and the full repertoire of adaptations within these substrates making adolescence a particularly susceptible developmental stage are not well understood. Prior work has demonstrated that a rodent model of adolescent social isolation (aSI) produces robust and persistent increases in phenotypes relevant to anxiety/stressor disorders and alcohol addiction, including anxiogenesis, deficits in fear extinction, and increased ethanol consumption. Here, we used extracellular field recordings in hippocampal slices to investigate adaptations in synaptic function and synaptic plasticity arising from aSI. We demonstrate that this early life stressor leads to enhanced excitatory synaptic transmission and decreased levels of long-term potentiation at hippocampal Schaffer collateral-CA1 synapses. Further, these changes were largely confined to the ventral hippocampus. As the ventral hippocampus is integral to neurocircuitry that mediates emotional behaviors, our results add to mounting evidence that aSI has profound effects on brain areas that regulate affective states. These studies also lend additional support to our recent proposal of the aSI model as a valid model of alcohol addiction vulnerability.

Developmental pathway genes and neural plasticity underlying emotional learning and stress-related disorders

The manipulation of neural plasticity as a means of intervening in the onset and progression of stress-related disorders retains its appeal for many researchers, despite our limited success in translating such interventions from the laboratory to the clinic. Given the challenges of identifying individual genetic variants that confer increased risk for illnesses like depression and post-traumatic stress disorder, some have turned their attention instead to focusing on so-called “master regulators” of plasticity that may provide a means of controlling these potentially impaired processes in psychiatric illnesses. The mammalian homolog of Tailless (TLX), Wnt, and the homeoprotein Otx2 have all been proposed to constitute master regulators of different forms of plasticity which have, in turn, each been implicated in learning and stress-related disorders. In the present review, we provide an overview of the changing distribution of these genes and their roles both during development and in the adult brain. We further discuss how their distinct expression profiles provide clues as to their function, and may inform their suitability as candidate drug targets in the treatment of psychiatric disorders.

Contribution of Vesicular Glutamate Transporters to Stress Response and Related Psychopathologies: Studies in VGluT3 Knockout Mice

Maintenance of the homeostasis in a constantly changing environment is a fundamental process of life. Disturbances of the homeostatic balance is defined as stress response and is induced by wide variety of challenges called stressors. Being the main excitatory neurotransmitter of the central nervous system glutamate is important in the adaptation process of stress regulating both the catecholaminergic system and the hypothalamic-pituitary-adrenocortical axis. Data are accumulating about the role of different glutamatergic receptors at all levels of these axes, but little is known about the contribution of different vesicular glutamate transporters (VGluT1-3) characterizing the glutamatergic neurons. Here we summarize basic knowledge about VGluTs, their role in physiological regulation of stress adaptation, as well as their contribution to stress-related psychopathology. Most of our knowledge comes from the VGluT3 knockout mice, as VGluT1 and 2 knockouts are not viable. VGluT3 was discovered later than, and is not as widespread as the VGluT1 and 2. It may co-localize with other transmitters, and participate in retrograde signaling; as such its role might be unique. Previous reports using VGluT3 knockout mice showed enhanced anxiety and innate fear compared to wild type. Moreover, these knockout animals had enhanced resting corticotropin-releasing hormone mRNA levels in the hypothalamus and disturbed glucocorticoid stress responses. In conclusion, VGluT3 participates in stress adaptation regulation. The neuroendocrine changes observed in VGluT3 knockout mice may contribute to their anxious, fearful phenotype.

Effectiveness of neurofeedback therapy for anxiety and stress in adults living with a chronic illness: a systematic review protocol

REVIEW QUESTION/OBJECTIVE

The objective of this review is to systematically examine the effectiveness of neurofeedback therapy for managing anxiety and stress in adults living with a chronic illness.The specific objectives are to identify which neurofeedback systems and/or protocols demonstrate effectiveness and determine the level of supporting evidence.The review question is as follows: What is the effectiveness of neurofeedback therapy for managing anxiety and stress in an adult population aged 18 years of age or older living with a chronic illness?

Measuring lifetime stress exposure and protective factors in life course research on racial inequality and birth outcomes

There has been a long-standing interest in better understanding how social factors contribute to racial disparities in health, including birth outcomes. A recent emphasis in this context has been on identifying the effects of stress exposure and protective factors experienced over the entire lifetime. Yet despite repeated calls for a life course approach to research on this topic, very few studies have actually assessed how stressors and protective factors occurring over women's lives relate to birth outcomes. We discuss this issue here by describing how challenges in the measurement of lifetime stress exposure and protective factors have prevented researchers from developing an empirically-based life course perspective on health. First, we summarize prevailing views on racial inequality and birth outcomes; second, we discuss measurement challenges that exist in this context; and finally, we describe both new tools and needed tools for assessing lifetime stress exposure and suggest opportunities for integrating information on stress exposure and psychosocial protective factors. We conclude that more studies are needed that integrate information about lifetime stress exposures and the protective factors that promote resilience against such exposures to inform policy and practice recommendations to reduce racial disparities in birth outcomes.

Cortical Plasticity in Depression

Neural plasticity is considered the neurophysiological correlate of learning and memory, although several studies have also noted that it plays crucial roles in a number of neurological and psychiatric diseases. Indeed, impaired brain plasticity may be one of the pathophysiological mechanisms that underlies both cognitive decline and major depression. Moreover, a degree of cognitive impairment is frequently observed throughout the clinical spectrum of mood disorders, and the relationship between depression and cognition is often bidirectional. However, most evidence for dysfunctional neural plasticity in depression has been indirect. Transcranial magnetic stimulation has emerged as a noninvasive tool for investigating several parameters of cortical excitability with the aim of exploring the functions of different neurotransmission pathways and for probing in vivo plasticity in both healthy humans and those with pathological conditions. In particular, depressed patients exhibit a significant interhemispheric difference in motor cortex excitability, an imbalanced inhibitory or excitatory intracortical neurochemical circuitry, reduced postexercise facilitation, and an impaired long-term potentiation-like response to paired-associative transcranial magnetic stimulation, and these symptoms may indicate disrupted plasticity. Research aimed at disentangling the mechanism by which neuroplasticity plays a role in the pathological processes that lead to depression and evaluating the effects of modulating neuroplasticity are needed for the field to facilitate more powerful translational research studies and identify novel therapeutic targets.

Grey matter abnormalities in children and adolescents with functional neurological symptom disorder

Objective

Functional neurological symptom disorder refers to the presence of neurological symptoms not explained by neurological disease. Although this disorder is presumed to reflect abnormal function of the brain, recent studies in adults show neuroanatomical abnormalities in brain structure. These structural brain abnormalities have been presumed to reflect long-term adaptations to the disorder, and it is unknown whether child and adolescent patients, with illness that is typically of shorter duration, show similar deficits or have normal brain structure.

Method

High-resolution, three-dimensional T1-weighted magnetic resonance images (MRIs) were acquired in 25 patients (aged 10–18 years) and 24 healthy controls. Structure was quantified in terms of grey matter volume using voxel-based morphometry. Post hoc, we examined whether regions of structural difference related to a measure of motor readiness to emotional signals and to clinical measures of illness duration, illness severity, and anxiety/depression.

Results

Patients showed greater volumes in the left supplementary motor area (SMA) and right superior temporal gyrus (STG) and dorsomedial prefrontal cortex (DMPFC) (corrected p < 0.05). Previous studies of adult patients have also reported alterations of the SMA. Greater SMA volumes correlated with faster reaction times in identifying emotions but not with clinical measures.

Conclusions

The SMA, STG, and DMPFC are known to be involved in the perception of emotion and the modulation of motor responses. These larger volumes may reflect the early expression of an experience-dependent plasticity process associated with increased vigilance to others' emotional states and enhanced motor readiness to organize self-protectively in the context of the long-standing relational stress that is characteristic of this disorder.

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We used high-resolution MRI to investigate brain structure in children presenting with acute functional neurological symptom disorder (FND).

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Patients had multiple antecedent stressors, a long-standing history of relational stress and at-risk attachment strategies.

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Patients had greater volumes in the SMA—where motor-, cognitive-, and emotion-processing signals interact to influence motor function.

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FND may involve experience-dependent changes in brain structure alongside experience-dependent changes in brain function.

Cortical Plasticity in Depression

Neural plasticity is considered the neurophysiological correlate of learning and memory, although several studies have also noted that it plays crucial roles in a number of neurological and psychiatric diseases. Indeed, impaired brain plasticity may be one of the pathophysiological mechanisms that underlies both cognitive decline and major depression. Moreover, a degree of cognitive impairment is frequently observed throughout the clinical spectrum of mood disorders, and the relationship between depression and cognition is often bidirectional. However, most evidence for dysfunctional neural plasticity in depression has been indirect. Transcranial magnetic stimulation has emerged as a noninvasive tool for investigating several parameters of cortical excitability with the aim of exploring the functions of different neurotransmission pathways and for probing in vivo plasticity in both healthy humans and those with pathological conditions. In particular, depressed patients exhibit a significant interhemispheric difference in motor cortex excitability, an imbalanced inhibitory or excitatory intracortical neurochemical circuitry, reduced postexercise facilitation, and an impaired long-term potentiation-like response to paired-associative transcranial magnetic stimulation, and these symptoms may indicate disrupted plasticity. Research aimed at disentangling the mechanism by which neuroplasticity plays a role in the pathological processes that lead to depression and evaluating the effects of modulating neuroplasticity are needed for the field to facilitate more powerful translational research studies and identify novel therapeutic targets.

Relationship of Genetic Variants With Procedural Pain, Anxiety, and Distress in Children

OBJECTIVE

This study used a candidate gene approach to examine genomic variation associated with pain, anxiety, and distress in children undergoing a medical procedure.

STUDY DESIGN

Children aged 4-10 years having an IV catheter insertion were recruited from three Midwestern children's hospitals. Self-report measures of pain, anxiety, and distress were obtained as well as an observed measure of distress. Samples were collected from children and biological parents for analysis of genomic variation. Genotyped variants had known or suspected association with phenotypes of interest. Analyses included child-only association and family-based transmission disequilibrium tests.

RESULTS

Genotype and phenotype data were available from 828 children and 376 family trios. Children were 50% male, had a mean age of 7.2 years, and were 84% White/non-Hispanic. In family-based analysis, one single-nucleotide polymorphism (SNP; rs1143629, interleukin ( IL1B) 1β) was associated with observed child distress at Bonferroni-corrected levels of significance ( p = .00013), while two approached significance for association with high state anxiety (rs6330 Nerve Growth Factor, Beta Subunit, [ NGFB]) and high trait anxiety (rs6265 brain-derived neurotrophic factor [ BDNF]). In the child-only analysis, multiple SNPs showed nominal evidence of relationships with phenotypes of interest. rs6265 BDNF and rs2941026 cholecystokinin B receptor had possible relationships with trait anxiety in child-only and family-based analyses.

CONCLUSIONS

Exploring genomic variation furthers our understanding of pain, anxiety, and distress and facilitates genomic screening to identify children at high risk of procedural pain, anxiety, and distress. Combined with clinical observations and knowledge, such explorations could help guide tailoring of interventions to limit procedure-related distress and identify genes and pathways of interest for future genotype-phenotype studies.

Optogenetic Examination of Prefrontal-Amygdala Synaptic Development

A brain network comprising the medial prefrontal cortex (mPFC) and amygdala plays important roles in developmentally regulated cognitive and emotional processes. However, very little is known about the maturation of mPFC-amygdala circuitry. We conducted anatomical tracing of mPFC projections and optogenetic interrogation of their synaptic connections with neurons in the basolateral amygdala (BLA) at neonatal to adult developmental stages in mice. Results indicate that mPFC-BLA projections exhibit delayed emergence relative to other mPFC pathways and establish synaptic transmission with BLA excitatory and inhibitory neurons in late infancy, events that coincide with a massive increase in overall synaptic drive. During subsequent adolescence, mPFC-BLA circuits are further modified by excitatory synaptic strengthening as well as a transient surge in feedforward inhibition. The latter was correlated with increased spontaneous inhibitory currents in excitatory neurons, suggesting that mPFC-BLA circuit maturation culminates in a period of exuberant GABAergic transmission. These findings establish a time course for the onset and refinement of mPFC-BLA transmission and point to potential sensitive periods in the development of this critical network.SIGNIFICANCE STATEMENT Human mPFC-amygdala functional connectivity is developmentally regulated and figures prominently in numerous psychiatric disorders with a high incidence of adolescent onset. However, it remains unclear when synaptic connections between these structures emerge or how their properties change with age. Our work establishes developmental windows and cellular substrates for synapse maturation in this pathway involving both excitatory and inhibitory circuits. The engagement of these substrates by early life experience may support the ontogeny of fundamental behaviors but could also lead to inappropriate circuit refinement and psychopathology in adverse situations.

The Role of Neural Plasticity in Depression: From Hippocampus to Prefrontal Cortex

Neural plasticity, a fundamental mechanism of neuronal adaptation, is disrupted in depression. The changes in neural plasticity induced by stress and other negative stimuli play a significant role in the onset and development of depression. Antidepressant treatments have also been found to exert their antidepressant effects through regulatory effects on neural plasticity. However, the detailed mechanisms of neural plasticity in depression still remain unclear. Therefore, in this review, we summarize the recent literature to elaborate the possible mechanistic role of neural plasticity in depression. Taken together, these findings may pave the way for future progress in neural plasticity studies.

Novel genetic loci associated with hippocampal volume

The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg=-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness.

Acute stress enhances the glutamatergic transmission onto basoamygdala neurons embedded in distinct microcircuits

Amygdala activation is known to be critical for the processing of stressful events in brain. Recent studies have shown that the projection neurons (PNs) in amygdala, although architecturally intermingled, are integrated into distinct microcircuits and thus play divergent roles in amygdala-related behaviors. It remains unknown how stress regulates the individual amygdala PNs embedded in distinct microcircuits. Here, by using retrograde tracing and electrophysiological recording in in vitro slices, we explored the modulation of acute immobilization stress (AIS) on the basoamygdala (BA) PNs projecting either to medial prefrontal cortex (mPFC) or elsewhere, which we designated as BA-mPFC and non-BA-mPFC PNs respectively. The results showed that in the control mice, both the excitatory and inhibitory postsynaptic currents (sEPSCs/sIPSCs) were comparable between these two subsets of BA PNs. The influences of AIS on sEPSCs and sIPSCs were overall similar between the two neuronal populations. It markedly increased the sEPSCs amplitude but left unaltered their frequency as well as the sIPSCs amplitude and frequency. Despite this, several differences emerged between the effects of AIS on the distribution of sEPSCs/sIPSCs frequency in these two groups of BA PNs. Similar changes were also observed in the sEPSCs/sIPSCs of the two PN populations from mice experiencing forced swimming stress. Their intrinsic excitability, on the other hand, was nearly unaltered following AIS. Our results thus suggest that acute stress recruit both BA-mPFC and non-BA-mPFC PNs mainly through enhancing the glutamatergic transmission they receive.

The direction of the relationship between symptoms of insomnia and psychiatric disorders in adolescents

BACKGROUND

This study assessed the direction of the relationship between symptoms of insomnia disorder, depression, various anxiety disorders and obsessive compulsive disorder (OCD) in adolescents after controlling for age, gender, chronotype, and outcome variable at baseline.

METHODS

Data was collected in eight high schools in Adelaide, South Australia, at two time-points approximately 6 months apart. The study was completed by 318 and 255 high school students at baseline and follow-up, respectively, aged 12-18 (M=14.96, SD=1.34) in grades 7-11 at baseline. Hierarchical regression analyses were used to assess each relationship, the first model controlling for age, gender and chronotype, and the second controlling for outcome variable at baseline.

RESULTS

Insomnia symptoms predicted and were predicted by symptoms of each psychiatric disorder in model 1. In model 2, insomnia symptoms predicted symptoms of depression, and vice-versa. Symptoms of insomnia also predicted symptoms of separation anxiety disorder (SAD) once SAD, but not vice-versa, in model 2. Symptoms of obsessive compulsive disorder (OCD) and social phobia (SP) predicted symptoms of insomnia disorder in model 2, but not vice-versa. Insomnia symptoms were no longer related to symptoms of other anxiety disorders in model 2.

LIMITATIONS

The use of self-report measures, and potential predisposing, precipitating, perpetuating or preventative factors were not assessed.

CONCLUSIONS

Symptoms of insomnia disorder are bidirectionally related to depressive symptoms independent from baseline symptoms, and unidirectionally related to symptoms of OCD and SP where OCD and SP are independent risk-factors of the development of insomnia symptoms.

Child sexual abuse and the development of psychiatric disorders: a neurobiological trajectory of pathogenesis

Child sexual abuse (CSA) is an important public health problem with long-standing neurobiological, developmental, and psychiatric abnormalities. The present review analyzes the long-term effects of CSA from a developmental, psychiatric morbidity, neurochemical and neurobiological perspective and then tries to posit a developmental neurobiological trajectory from CSA to the genesis of psychopathology in later life. The role of various neurotransmitters such as serotonin and dopamine affected by CSA are discussed. Serotonin abnormalities have been reported in various studies among participants exposed to CSA. Structures such as the prefrontal cortex, superior temporal gyrus, corpus callosum, parietal lobes, hippocampus, and cerebellum all demonstrate volumetric and structural changes in response to the trauma of CSA. Neurocognitive studies demonstrate memory and spatial awareness as well as decrements in general cognitive performance and memory when compared to normal individuals. The hypothalamic-pituitary-adrenal axis has also been implicated in CSA, and there is an alteration in corticotropin-releasing hormone response due to the continuous cumulative trauma of CSA. This paper also reviews a section on the role of genetic and epigenetic factors in the development of psychiatric disorders as a result of exposure to episodes of CSA where studies have demonstrated changes in DNA methylation in response to CSA. This review tries to hypothesize a developmental trajectory framework which is individual for every case where exposure to CSA may lead to psychopathology and psychiatric morbidity later in life. Rapid and emerging fields such as developmental traumatology in relation to CSA are also discussed.

Hippocampal Sirtuin 1 Signaling Mediates Depression-like Behavior

BACKGROUND

Although depression is the leading cause of disability worldwide, its pathophysiology is poorly understood. Recent evidence has suggested that sirtuins (SIRTs) play a key role in cognition and synaptic plasticity, yet their role in mood regulation remains controversial. Here, we aimed to investigate whether SIRT function is associated with chronic stress-elicited depression-like behaviors and neuronal atrophy.

METHODS

We measured SIRT expression and activity in a mouse model of depression. We injected mice with a SIRT1 activator or inhibitor and measured their depression-like behaviors and dendritic spine morphology. To assess the role of SIRT1 directly, we used a viral-mediated gene transfer to overexpress the wild-type SIRT1 or dominant negative SIRT1 and evaluated their depression-like behaviors. Finally, we examined the role of extracellular signal-regulated protein kinases 1 and 2, a potential downstream target of SIRT1, in depression-like behavior.

RESULTS

We found that chronic stress reduced SIRT1 activity in the dentate gyrus of the hippocampus. Pharmacologic and genetic inhibition of hippocampal SIRT1 function led to an increase in depression-like behaviors. Conversely, SIRT1 activation blocked both the development of depression-related phenotypes and aberrant dendritic structures elicited by chronic stress exposure. Furthermore, hippocampal SIRT1 activation increased the phosphorylation level of extracellular signal-regulated protein kinases 1 and 2 in the stressed condition, and viral-mediated activation and inhibition of hippocampal extracellular signal-regulated protein kinase 2 led to antidepressive and prodepressive behaviors, respectively.

CONCLUSIONS

Our results suggest that the hippocampal SIRT1 pathway contributes to the chronic stress-elicited depression-related phenotype and aberrant dendritic atrophy.

Stress transgenerationally programs metabolic pathways linked to altered mental health

Stress is among the primary causes of mental health disorders, which are the most common reason for disability worldwide. The ubiquity of these disorders, and the costs associated with them, lends a sense of urgency to the efforts to improve prediction and prevention. Down-stream metabolic changes are highly feasible and accessible indicators of pathophysiological processes underlying mental health disorders. Here, we show that remote and cumulative ancestral stress programs central metabolic pathways linked to mental health disorders. The studies used a rat model consisting of a multigenerational stress lineage (the great-great-grandmother and each subsequent generation experienced stress during pregnancy) and a transgenerational stress lineage (only the great-great-grandmother was stressed during pregnancy). Urine samples were collected from adult male F4 offspring and analyzed using 1H NMR spectroscopy. The results of variable importance analysis based on random variable combination were used for unsupervised multivariate principal component analysis and hierarchical clustering analysis, as well as metabolite set enrichment analysis (MSEA) and pathway analysis. We identified distinct metabolic profiles associated with the multigenerational and transgenerational stress phenotype, with consistent upregulation of hippurate and downregulation of tyrosine, threonine, and histamine. MSEA and pathway analysis showed that these metabolites are involved in catecholamine biosynthesis, immune responses, and microbial host interactions. The identification of metabolic signatures linked to ancestral programming assists in the discovery of gene targets for future studies of epigenetic regulation in pathogenic processes. Ultimately, this research can lead to biomarker discovery for better prediction and prevention of mental health disorders.

Structural and functional plasticity of dendritic spines - root or result of behavior?

Dendritic spines are multifunctional integrative units of the nervous system and are highly diverse and dynamic in nature. Both internal and external stimuli influence dendritic spine density and morphology on the order of minutes. It is clear that the structural plasticity of dendritic spines is related to changes in synaptic efficacy, learning and memory and other cognitive processes. However, it is currently unclear whether structural changes in dendritic spines are primary instigators of changes in specific behaviors, a consequence of behavioral changes, or both. In this review, we first examine the basic structure and function of dendritic spines in the brain, as well as laboratory methods to characterize and quantify morphological changes in dendritic spines. We then discuss the existing literature on the temporal and functional relationship between changes in dendritic spines in specific brain regions and changes in specific behaviors mediated by those regions. Although technological advancements have allowed us to better understand the functional relevance of structural changes in dendritic spines that are influenced by environmental stimuli, the role of spine dynamics as an underlying driver or consequence of behavior still remains elusive. We conclude that while it is likely that structural changes in dendritic spines are both instigators and results of behavioral changes, improved research tools and methods are needed to experimentally and directly manipulate spine dynamics in order to more empirically delineate the relationship between spine structure and behavior.

HPA Axis Interactions with Behavioral Systems

Perhaps the most salient behaviors that individuals engage in involve the avoidance of aversive experiences and the pursuit of pleasurable experiences. Engagement in these behaviors is regulated to a significant extent by an individual's hormonal milieu. For example, glucocorticoid hormones are produced by the hypothalamic-pituitary-adrenocortical (HPA) axis, and influence most aspects of behavior. In turn, many behaviors can influence HPA axis activity. These bidirectional interactions not only coordinate an individual's physiological and behavioral states to each other, but can also tune them to environmental conditions thereby optimizing survival. The present review details the influence of the HPA axis on many types of behavior, including appetitively-motivated behaviors (e.g., food intake and drug use), aversively-motivated behaviors (e.g., anxiety-related and depressive-like) and cognitive behaviors (e.g., learning and memory). Conversely, the manuscript also describes how engaging in various behaviors influences HPA axis activity. Our current understanding of the neuronal and/or hormonal mechanisms that underlie these interactions is also summarized. © 2016 American Physiological Society. Compr Physiol 6:1897-1934, 2016.

Physical Exercise Counteracts Stress-induced Upregulation of Melanin-concentrating Hormone in the Brain and Stress-induced Persisting Anxiety-like Behaviors

Chronic stress induces anxiety disorders, whereas physical exercise is believed to help people with clinical anxiety. In the present study, we investigated the mechanisms underlying stress-induced anxiety and its counteraction by exercise using an established animal model of anxiety. Mice treated with restraint for 2 h daily for 14 days exhibited anxiety-like behaviors, including social and nonsocial behavioral symptoms, and these behavioral impairments lasted for more than 12 weeks after the stress treatment was removed. Despite these lasting behavioral changes, wheel-running exercise treatment for 1 h daily from post-stress days 1 - 21 counteracted anxiety-like behaviors, and these anxiolytic effects of exercise persisted for more than 2 months, suggesting that anxiolytic effects of exercise stably induced. Repeated restraint treatment up-regulated the expression of the neuropeptide, melanin-concentrating hormone (MCH), in the lateral hypothalamus, hippocampus, and basolateral amygdala, the brain regions important for emotional behaviors. In an in vitro study, treatment of HT22 hippocampal cells with glucocorticoid increased MCH expression, suggesting that MCH upregulation can be initially triggered by the stress hormone, corticosterone. In contrast, post-stress treatment with wheel-running exercise reduced the stress-induced increase in MCH expression to control levels in the lateral hypothalamus, hippocampus and basolateral amygdala. Administration of an MCH receptor antagonist (SNAP94847) to stress-treated mice was therapeutic against stress-induced anxiety-like behaviors. These results suggest that repeated stress produces long-lasting anxiety-like behaviors and upregulates MCH in the brain, while exercise counteracts stress-induced MCH expression and persisting anxiety-like behaviors.