Neurobiology of Stress最新文献

Chronic stress is well known to erode cognitive functions. Yet, our understanding of how repeated stress exposure impacts one of the fundamental bases of cognition: sensory processing, remains limited. The posterior parietal cortex (PPC) is a high order visual region, known for its role in visually guided decision making, multimodal integration, attention, and working memory. Here, we used functional measures to determine how repeated exposure to multiple concurrent stressors (RMS) affects sensory processing in the PPC in adult male mice. A longitudinal experimental design, repeatedly surveying the same population of neurons using in vivo two-photon imaging, revealed that RMS disrupts the balanced turnover of visually responsive cells in layer 2/3 of the PPC. Across the population, RMS-induced changes in visual responsiveness followed a bimodal distribution suggesting idiosyncratic stress effects. In cells that maintained their responsiveness across recording sessions, we found that stress reduced visual response magnitudes and feature selectivity. While we did not observe stress-induced elimination of excitatory synapses, noise correlation statistics indicated that RMS altered visual input to the neuronal population. The impact of RMS was restricted to visually evoked responses and was not evident in neuronal activity associated with locomotion onset. Together, our results indicate that despite no apparent synaptic reorganization, stress exposure in adulthood can disrupt sensory processing in the PPC, with the effects showing remarkable individual variation.

Introduction

At the maternal-fetal interface in pregnancy, stress during pregnancy can lead to an increased vulnerability to later psychopathology of the fetus. Potential mediators of this association have scarcely been studied and may include early alterations of fetal brain-derived neurotrophic factor (BDNF). Amniotic fluid is of particular interest for effects on fetal endocrine alterations, as the assessment in amniotic fluid allows for measurements over a time integral. This study hypothesized that maternal psychometrics, socioeconomic status and glucocorticoids are related to BDNF levels in amniotic fluid at birth. The association of fetal BDNF with newborn anthropometrics was tested.

Methods

Women near term who underwent elective cesarean section and their newborns were investigated (n = 37). Maternal psychometrics, socioeconomic status and glucocorticoids (the sum of cortisol and cortisone) in amniotic fluid at birth were analyzed for an association with fetal BDNF in amniotic fluid at birth. Newborn anthropometrics were assessed by length, weight, head circumference and gestational age at birth.

Results

In bivariate analysis, maternal psychometrics and socioeconomic status were not related to fetal BDNF in amniotic fluid at birth. The sum of cortisol and cortisone related to increased fetal BDNF in amniotic fluid at birth (r = 0.745, p < 0.001). BDNF in amniotic fluid was associated negatively with fetal birth weight per gestational age (r = −0.519, p < 0.001), length per gestational age (r = −0.374, p = 0.023), head circumference per gestational age (r = −0.508, p = 0.001), but not with gestational age at birth. In multiple regression analysis, the sum of cortisol and cortisone (p < 0.001) and birth weight per gestational age (p = 0.012) related to higher fetal BDNF levels in amniotic fluid at birth (R² = 0.740, p < 0.001) when controlling for fetal sex and maternal age. Head circumference per gestational age predicted fetal BDNF with borderline significance (p = 0.058) when controlling for confounders.

Conclusion

Glucocorticoids in amniotic fluid were positively associated with high fetal BDNF at birth, which may be an adaptive fetal response. Maternal psychological variables and socioeconomic status did not link to fetal BDNF. Birth weight and head circumference per gestational age were inversely associated with fetal BDNF at birth, which may represent a compensatory upregulation of BDNF in fetuses with low anthropometrics. Longitudinal studies are needed to assess the role of stress during pregnancy on later offspring development. The analysis of additional fetal growth factors and inflammation upon maternal stress in further biomaterials such as the placenta is warranted, to understand mechanistic alterations of how maternal stress links to fetal development and an increased vulnerability for psychopathology.

Impairments in sleep and affect regulation are evident across a wide range of mental disorders. Understanding the sleep factors that relate to affect regulatory difficulties will inform mechanistic understanding and aid in treatment. Despite rising interest, some research challenges in this area include integrating across different clinical and non-clinical literatures investigating the role of sleep architecture (measured with polysomnography) and experimentally manipulated sleep, as well as integrating more explicit versus implicit affect regulation processes. In this comprehensive review, we use a unifying framework to examine sleep's relationship with implicit-automatic regulation and explicit-controlled regulation, both of which are relevant to mental health (e.g., PTSD and depression). Many studies of implicit-automatic regulation (e.g., fear extinction and safety learning) demonstrate the importance of sleep, and REM sleep specifically. Studies of explicit-controlled regulation (e.g., cognitive reappraisal and expressive suppression) are less consistent in their findings, with results differing depending on the type of affect regulation and/or way that sleep was measured or manipulated. There is a clear relationship between objective sleep and affect regulation processes. However, there is a need for 1) more studies focusing on sleep and explicit-controlled affect regulation; 2) replication with the same types of regulation strategies; 3) more studies experimentally manipulating sleep to examine its impact on affect regulation and vice versa in order to infer cause and effect; and 4) more studies looking at sleep's impact on next-day affect regulation (not just overnight change in affect reactivity).

Chronic ethanol dependence and withdrawal activate corticotropin releasing factor (CRF)-containing GABAergic neurons in the medial prefrontal cortex (mPFC), which tightly regulate glutamatergic pyramidal neurons. Using male CRF1:GFP reporter mice, we recently reported that CRF1-expressing (mPFC^CRF1+) neurons predominantly comprise mPFC prelimbic layer 2/3 pyramidal neurons, undergo profound adaptations following chronic ethanol exposure, and regulate anxiety and conditioned rewarding effects of ethanol. To explore the effects of acute and chronic ethanol exposure on glutamate transmission, the impact of chronic alcohol on spine density and morphology, as well as persistent changes in dendritic-related gene expression, we employed whole-cell patch-clamp electrophysiology, diOlistic labeling for dendritic spine analysis, and dendritic gene expression analysis to further characterize mPFC^CRF1+ and mPFC^CRF1− prelimbic layer 2/3 pyramidal neurons. We found increased glutamate release in mPFC^CRF1+ neurons with ethanol dependence, which recovered following withdrawal. In contrast, we did not observe significant changes in glutamate transmission in neighboring mPFC^CRF1− neurons. Acute application of 44 mM ethanol significantly reduced glutamate release onto mPFC^CRF1+ neurons, which was observed across all treatment groups. However, this sensitivity to acute ethanol was only evident in mPFC^CRF1− neurons during withdrawal. In line with alterations in glutamate transmission, we observed a decrease in total spine density in mPFC^CRF1+ neurons during dependence, which recovered following withdrawal, while again no changes were observed in mPFC^CRF− neurons. Given the observed decreases in mPFC^CRF1+ stubby spines during withdrawal, we then identified persistent changes at the dendritic gene expression level in mPFC^CRF1+ neurons following withdrawal that may underlie these structural adaptations. Together, these findings highlight the varying responses of mPFC^CRF1+ and mPFC^CRF1− cell-types to acute and chronic ethanol exposure, as well as withdrawal, revealing specific functional, morphological, and molecular adaptations that may underlie vulnerability to ethanol and the lasting effects of ethanol dependence.

Post-traumatic stress disorder (PTSD) is a debilitating disorder characterized by excessive fear, hypervigilance, and avoidance of thoughts, situations or reminders of the trauma. Among these symptoms, relatively little is known about the etiology of pathological avoidance. Here we sought to determine whether acute stress influences avoidant behavior in adult male and female rats. We used a stress procedure (unsignaled footshock) that is known to induce long-term sensitization of fear and potentiate aversive learning. Rats were submitted to the stress procedure and, one week later, underwent two-way signaled active avoidance conditioning (SAA). In this task, rats learn to prevent an aversive outcome (shock) by performing a shuttling response when exposed to a warning signal (tone). We found that acute stress significantly enhanced SAA acquisition rate in females, but not males. Female rats exhibited significantly greater avoidance responding on the first day of training relative to controls, reaching similar levels of performance by the second day. Males that underwent the stress procedure showed similar rates of acquisition to controls but exhibited resistance to extinction. This was manifest as both elevated avoidance and intertrial responding across extinction days relative to non-stressed controls, an effect that was not observed in females. In a second experiment, acute stress sensitized footshock unconditioned responses in males, not females. However, males and females exhibited similar levels of stress-enhanced fear learning (SEFL), which was expressed as sensitized freezing to a shock-paired context. Together, these results reveal that acute stress facilitates SAA performance in both male and female rats, though the nature of this effect is different in the two sexes. We did not observe sex differences in SEFL, suggesting that the stress-induced sex difference in performance was selective for instrumental avoidance. Future work will elucidate the neurobiological mechanisms underlying the differential effect of stress on instrumental avoidance in male and female rats.

Many everyday decisions, including those concerning our health, finances and the environment, involve choosing between a smaller but imminent reward (e.g., €20 now) and a later but larger reward (e.g., €40 in a month). The extent to which an individual prefers smaller imminent rewards over larger delayed rewards can be measured using delay discounting tasks. Acute stress induces a cascade of biological and psychological responses with potential consequences for how individuals think about the future, process rewards, and make decisions, all of which can impact delay discounting. Several studies have shown that individuals focus more on imminent rewards under stress. These findings have been used to explain why individuals make detrimental choices under acute stress. Yet, the evidence linking acute stress to delay discounting is equivocal. To address this uncertainty, we conducted a meta-analysis of 11 studies (14 effects) to systematically quantify the effects of acute stress on monetary delay discounting. Overall, we find no effect of acute stress on delay discounting, compared to control conditions (SMD = −0.18, 95% CI [-0.57, 0.20], p = 0.32). We also find that neither the gender/sex of the participants, the type of stressor (e.g., physical vs. psychosocial) nor whether monetary decisions were hypothetical or incentivized (i.e. monetary decisions were actually paid out) moderated the impact of acute stress on monetary delay discounting. We argue that establishing the effects of acute stress on the separate processes involved in delay discounting, such as reward valuation and prospection, will help to resolve the inconsistencies in the field.

Chronic pain can induce mood disorders and cognitive dysfunctions, such as anxiety, depression, and learning and memory impairment in humans. However, the specific neural network involved in anxiety- and depression-like behaviors and learning and memory impairment caused by chronic pain remains poorly understood. In this study, behavioral test results showed that chronic pain induced anxiety- and depression-like behaviors, and learning and memory impairment in male mice. c-Fos immunofluorescence and fiber photometry recording showed that glutamatergic neurons in the LH of mice with chronic pain were selectively activated. Next, the glutamatergic neurons of LH in normal mice were activated using optogenetic and chemogenetic methods, which recapitulates some of the depressive-like behaviors, as well as memory impairment, but not anxiety-like behavior. Finally, inhibition of glutamatergic neurons in the LH of mice with chronic pain, effectively relieved anxiety- and depression-like behaviors and learning and memory impairment. Taken together, our findings suggest that hyperexcitation of glutamatergic neurons in the LH is involved in depression-like behavior and learning and memory impairment induced by chronic pain.

Adverse early-life experiences (ELA) affect a majority of the world's children. Whereas the enduring impact of ELA on cognitive and emotional health is established, there are no tools to predict vulnerability to ELA consequences in an individual child. Epigenetic markers including peripheral-cell DNA-methylation profiles may encode ELA and provide predictive outcome markers, yet the interindividual variance of the human genome and rapid changes in DNA methylation in childhood pose significant challenges. Hoping to mitigate these challenges we examined the relation of several ELA dimensions to DNA methylation changes and outcome using a within-subject longitudinal design and a high methylation-change threshold.

DNA methylation was analyzed in buccal swab/saliva samples collected twice (neonatally and at 12 months) in 110 infants. We identified CpGs differentially methylated across time for each child and determined whether they associated with ELA indicators and executive function at age 5. We assessed sex differences and derived a sex-dependent ‘impact score’ based on sites that most contributed to methylation changes.

Changes in methylation between two samples of an individual child reflected age-related trends and correlated with executive function years later. Among tested ELA dimensions and life factors including income to needs ratios, maternal sensitivity, body mass index and infant sex, unpredictability of parental and household signals was the strongest predictor of executive function. In girls, high early-life unpredictability interacted with methylation changes to presage executive function. Thus, longitudinal, within-subject changes in methylation profiles may provide a signature of ELA and a potential predictive marker of individual outcome.

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the “internalizing” bred Low Responder (bLR) line versus the “externalizing” bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

Stressors can initiate a cascade of central and peripheral changes that modulate mesocorticolimbic dopaminergic circuits and, ultimately, behavioral response to rewards. Driven by the absence of conclusive evidence on this topic and the Research Domain Criteria framework, random-effects meta-analyses were adopted to quantify the effects of acute stressors on reward responsiveness, valuation, and learning in rodent and human subjects.

In rodents, acute stress reduced reward responsiveness (g = −1.43) and valuation (g = −0.32), while amplifying reward learning (g = 1.17). In humans, acute stress had marginal effects on valuation (g = 0.25), without affecting responsiveness and learning. Moderation analyses suggest that acute stress neither has unitary effects on reward processing in rodents nor in humans and that the duration of the stressor and specificity of reward experience (i.e., food vs drugs) may produce qualitatively and quantitatively different behavioral endpoints.

Subgroup analyses failed to reduce heterogeneity, which, together with the presence of publication bias, pose caution on the conclusions that can be drawn and point to the need of guidelines for the conduction of future studies in the field.