Neurocircuitry of stress: central control of the hypothalamo-pituitary-adrenocortical axis

Corticosterone rapidly modulates dorsomedial hypothalamus serotonin and behavior in an estrogen- and progesterone-dependent manner in adult female rats: potential role of organic cation transporter 3 (OCT3)

Previous studies have shown that corticosterone rapidly alters extracellular serotonin (5-hydroxytryptamine; 5-HT) concentrations in the dorsomedial hypothalamus (DMH) of adult male rats, suggesting a role for corticosterone actions in the DMH in regulation of physiological and behavioral responses. Whether or not corticosterone also rapidly alters extracellular serotonin concentrations in the DMH of female rats, and the dependence of this effect on ovarian hormones, is not known. To determine the effects of 17β-estradiol (E2), progesterone (P), and corticosterone on extracellular concentrations of serotonin in the DMH, corticosterone and/or P were delivered into the DMH of ovariectomized rats via reverse microdialysis in E2-primed rats. Combined, but not separate, delivery of corticosterone and P into the DMH rapidly and transiently increased extracellular 5-HT concentrations, a result that was dependent upon circulating E2. This effect of corticosterone on DMH 5-HT was replicated by local perfusion of the organic cation transporter 3 (OCT3) competitive inhibitor normetanephrine. Intra-DMH infusions of either corticosterone or normetanephrine also reversibly suppressed lordosis responses in E2 + P-primed females. These results suggest that ovarian hormones in combination with corticosterone modulate OCT3-mediated 5-HT clearance in the DMH, potentially representing an adaptive mechanism that allows sexually receptive females to respond rapidly to acute stressors.

"Maladaptive stress-coping behavior in CX3CR1-deficient mice: Impact of adolescent stress and alcohol exposure on neuroimmune responses and inflammation"

The CX3CL1/CX3CR1 chemokine axis regulates synaptic pruning, plasticity, and stress-related behaviors, influencing resilience or vulnerability to psychiatric disorders. Adolescence, a critical period for neuroimmune development, increases susceptibility to stressors. This study investigated how adolescent restraint stress and alcohol exposure affect stress-coping behavior, neuroimmune signaling, and systemic inflammation in adult wild-type (WT) and CX3CR1 knock-out (KO) mice. Eighty-one male and female WT and KO mice were assigned to control (non-stressed, saline-treated), stress (stressed, saline-treated), alcohol (non-stressed, alcohol-treated), and stress + alcohol (stressed, alcohol-treated) groups. Behavioral responses were evaluated using the tail suspension test. Hypothalamic gene expression of CX3CL1/CX3CR1, corticotropin-releasing hormone (CRH), and neuropeptide Y (NPY) systems was analyzed alongside plasma corticosterone, adrenocorticotropic hormone (ACTH), CX3CL1, and inflammatory mediators. Adolescent stress-but not alcohol-increased plasma CX3CL1 levels, which inversely correlated with immobility time in WT mice. KO mice displayed higher baseline immobility than WT mice, whereas stress and/or alcohol paradoxically reduced immobility. These behavioral effects were reproduced by pharmacological inhibition of CX3CR1. Additionally, KO mice showed disrupted hypothalamic expression of multiple genes in the CRH pathway and Npy1r, attenuated corticosterone responses to stress, and abolished ACTH-corticosterone correlation, suggesting HPA axis dysregulation. KO mice also exhibited exacerbated inflammatory responses to stress and alcohol, including elevated IL-17A/F, IL-11, and IFN-β1 levels. CX3CR1 deficiency disrupts neuroimmune homeostasis, leading to maladaptive stress-coping behaviors and heightened inflammatory reactivity. These findings underscore the protective role of the CX3CL1/CX3CR1 axis in neuroinflammatory regulation and stress resilience, supporting CX3CR1 as a potential therapeutic target in stress-related disorders.

Effect of chronic corticosterone administration on acute stress-mediated gene expression in the cortex and hippocampus of male mice

Corticosterone plays an important role in the stress response, physiological regulation, and development of stress-related psychiatric disorders. Although several studies have demonstrated that chronic corticosterone induces anxiety- or depressive-related behaviors in mice, it remains unclear whether chronic corticosterone administration affects gene expression in the brain during the stress response. This study investigated whether chronic corticosterone administration has a significant effect on stress-related gene expression in the brain. Therefore, mice were chronically treated with corticosterone in drinking water and gene expression was analyzed by quantitative PCR (qPCR). Moreover, restraint stress was acutely applied as a novel stressor in mice chronically treated with corticosterone in the cortex and hippocampus. We initially found that chronic corticosterone administration altered glucocorticoid signaling-mediated gene expression, such as FK506 binding protein 5 (Fkbp5) and glucocorticoid-inducible kinase 1 (Sgk1), in the cortex and hippocampus of mice. Next, we found that restraint stress exposure elevated Fkbp5 expression in the vehicle group; however, chronic corticosterone administration occluded further induction of Fkbp5 expression after restraint stress exposure. In addition, pro-inflammatory cytokines tumor necrosis factor α (Tnfa) and interleukin-1β (Il1b) mRNA expression in the cortex and hippocampus were remarkably enhanced by restraint stress in corticosterone-treated mice, but not in the vehicle group. Collectively, our results demonstrated that chronic corticosterone administration modulates glucocorticoid signaling and uncovered the robust induction of pro-inflammatory cytokines after restraint stress exposure in chronically corticosterone-treated mice. These mechanisms may be involved in the molecular basis for the onset of stress-related mental illnesses.

Decision-making, affective states, and self-efficacy of students in the high-stress situation of a 192 m bungee jump - a randomised crossover trial

Decision-making involves rational and affective pathways, with high-stress potentially altering decision - making and affective states, alongside affecting behavioural variables. This study aims to analyze decision-making, affective states, and variables related to behaviour in a real-life high-stress scenario (bungee - jumping).Using a within-subject crossover-design, 19 participants (47% female, aged 23.0 ± 2.1 years) completed a 192 m bungee-jump and a 1 m control jump. Decision-making tests, affective states, and behavioural variables were assessed. Condition-by-time fully repeated measures analyses of variance were employed.Balloon Analogue Risk Task (BART) revealed significantly higher values pre - and post-bungee-jump compared to the control jump. Accuracy and average reaction time on the Go/No-Go task remained consistent across conditions and time points. Pre-action self-efficacy was significantly higher after the bungee - jump compared to the control jump. Affective valence demonstrated a significant condition-by-time interaction, presenting low values immediately before the bungee-jump.A high-stress situation impacted risk-taking but not inhibition in decision-making, associated with heightened arousal and affective valence. Anticipatory effects emerged significantly in decision-making and affective states. Furthermore, participants exhibited increased confidence in approaching subsequent tasks post - bungee - jump. Therefore, high-stress situations may enhance pre-action self-efficacy, although potential implications for riskier decision-making should be acknowledged.

Stk24 deficiency causes disrupted hippocampal neurogenesis and anxiety-like behavior in mice

Protein kinases regulate protein activity through phosphorylation, and many have been reported to participate in brain development. Among them, serine/threonine-protein kinase 24 (STK24) is believed to influence apoptosis, spinal synaptogenesis, and neuronal migration. Despite its recognized roles, the functions of STK24 in the brain remains insufficiently explored. Here, we present an in vivo study of brain-specific Stk24 conditional knockout mice. We investigate the impact of Stk24 deletion through histological analysis, behavior assays, and the molecular changes. In our results, Stk24 deletion disrupts the hippocampal formation during development and decreased subsequent adult hippocampal neurogenesis whilst neuronal morphology is relatively unaffected. Additionally, Stk24-deficient mice exhibit anxiety-like behavior and altered stress responses, featuring increased hippocampal neuronal activity, dysregulated HPA axis reactivity, and modified expression patterns of glucocorticoid receptor signaling-related genes. In conclusion, our findings highlight the involvement of Stk24 in brain development, adult hippocampal neurogenesis, as well as anxiety and stress responses.

Primary ciliary protein kinase A activity in the prefrontal cortex modulates stress in mice

Primary cilia are cellular antennae emanating from vertebrate cell surfaces to sense and transduce extracellular signals intracellularly to regulate cell behavior and function. However, their signal sensing and physiological functions in neocortical neurons remain largely unclear. Here, we show that, in response to various animal stressors, primary cilia in the mouse prefrontal cortex (PFC) exhibit consistent axonemal elongation. Selective removal of excitatory neuron primary cilia in the prefrontal but not sensory cortex leads to a reduction in animal stress sensing and response. Treatment with corticosterone, the major stress hormone, elicits an increase in primary ciliary cyclic adenosine 3',5'-monphosphate (cAMP) level in PFC excitatory neurons and a decrease in neuronal excitability dependent on primary cilia. Suppression of primary ciliary protein kinase A (PKA) activity in PFC excitatory neurons reduces animal stress. These results suggest that excitatory neurons in the PFC are involved in sensing and regulating animal stress via primary ciliary cAMP/PKA signaling.

Cortisol in schizophrenia spectrum disorders: A comprehensive meta-analysis

Schizophrenia spectrum disorders (SSD) are characterized by alterations in cortisol levels across various parameters, including stress reactivity, hair cortisol, and baseline levels, which may be influenced by antipsychotic treatment. To provide a comprehensive overview of cortisol dysregulation in SSD, we conducted meta-analyses assessing (1) the effects of antipsychotic treatment in SSD patients, and additionally comparing cortisol in SSD patients versus healthy controls (HC) (2) following stress induction (metabolic, physiological, psychological stressors), (3) in hair and (4) baseline levels. Systematic literature searches in PubMed, Web of Science, and PsycINFO (November 2024) identified 121 studies (9049 SSD patients) for inclusion. Meta-analytic results revealed that antipsychotic treatment significantly reduced cortisol levels in SSD (k = 16, g = -0.480, 95 % CI [-0.818, -0.142], p = 0.005). Additionally, compared to HC, SSD was associated with reduced cortisol suppression following dexamethasone exposure (k = 9, g = 0.299, 95 % CI [0.091, 0.507], p = 0.005) and with elevated baseline cortisol levels in the morning (k = 71, g = 0.38, 95 % CI [0.210, 0.546], p < 0.001) and evening (k = 11, g = 0.368, 95 % CI [0.076, 0.661], p = 0.014). However, there were no significant group differences in afternoon baseline cortisol, hair cortisol or cortisol reactivity to stress (p > 0.05). These findings offer a detailed understanding of cortisol alterations in SSD and improve our understanding of HPA axis dysregulation in SSD.

Cross-species dissection of the modular role of the ventral tegmental area in depressive disorders

Depressive disorders, including major depressive disorder (MDD), represent one of the most prevalent set of disorders worldwide. MDD is characterized by a range of cognitive, behavioral, and neurobiological changes that contribute to the vast array of symptom profiles that make this disorder particularly difficult to treat. A multitude of established evidence suggests a role for the dopamine system, stemming in part from the ventral tegmental area (VTA), in mediating symptoms and behavioral changes that underlie depression. Developments in cutting-edge technologies in pre-clinical models of depressive phenotypes, such as retrograde tracing, electrophysiological recordings, immunohistochemistry, and molecular profiling, have allowed a deeper characterization of singular VTA neuron molecular, physiological, and projection properties. These developments have highlighted that the VTA is not a homogenous cell population but instead comprises vast cellular diversity that underscores its modular role across various functions related to reward processing, aversion, salience processing, learning and motivation. In this review, we begin by introducing the various cell types and brain regions that comprise the VTA circuitry. Then, we introduce the role of the VTA in reward processing as it compares to aversion processing. Next, we characterize distinct neural pathways within the VTA circuitry to understand the effects of chronic social and non-social stress and tie together how these neurobiological changes manifest into specific behavioral phenotypes. Finally, we relate these preclinical findings to clinical findings to parse the heterogeneity of depressive phenotypes and explain the efficacy of recent novel pharmacological interventions that may target the VTA in MDD.

Influence of Primary Neurologic Disease on Cardiovascular Health in Females

Neurocardiology is an interdisciplinary field that examines the complex interactions between the nervous and the cardiovascular systems, exploring how neurological processes, such as autonomic nervous system regulation and brain-heart communication impact heart function and contribute to cardiovascular health and disease. Although much of the focus on cardiovascular health has centered on traditional risk factors, the influence of the nervous system, especially in females, is increasingly recognized as a key determinant of cardiovascular outcomes. This article reviews existing literature on the neurological mechanisms that impact cardiovascular function in females. Specifically, we analyze how primary neurological disorders including cerebrovascular disease, headache disorders, and multiple sclerosis have specific downstream effects on cardiac function. By understanding the complex relationship between neurological and cardiovascular health, this review highlights the need for sex-specific approaches to prevention, diagnosis, and treatment of cardiovascular disease in females, ultimately encouraging the discovery of more effective care strategies and improving health outcomes.

Integrated Microbiome and Metabolomics Analysis Reveals Altered Aggressive Behaviors in Broiler Chickens Showing Different Tonic Immobility

Tonic immobility (TI) serves as an indicator of innate stress response recovery in poultry. Broilers with different TI phenotypes exhibit varying levels of aggressive behavior, which can significantly impact their welfare. However, the influences of TI phenotypes on broiler aggression remain largely unexplored. In this study, broiler chickens were stratified into two distinct phenotypic groups based on the TI duration: short TI (STI) and long TI (LTI). The impacts of TI phenotypes on broiler aggression were investigated by analyzing cecal intestinal morphology, cecal bacteria, plasma metabolites, and corticosterone levels. Compared to LTI broilers, STI broilers showed significantly reduced plasma corticosterone (CORT) levels (p < 0.05) and a decreased frequency of aggressive behaviors, including dominant and subdominant types (p < 0.01). Histological analysis revealed that STI broilers have an increased duodenal villus height and villus-height-to-crypt-depth ratio (p < 0.01), a decreased jejunal crypt depth with an increased villus-height-to-crypt-depth ratio (p < 0.01), and a reduced ileal crypt depth and villus height (p < 0.01) compared to LTI broilers. 16S rDNA sequencing and Linear discriminant analysis effect size (LefSe) identified differential cecal bacterial abundance, notably in the genus cc115 belonging to Firmicutes. Specific microbiota in LTI broilers exhibited significant positive correlations with aggressive behavior and plasma corticosterone, while those in STI broilers showed significant negative correlations. Untargeted plasma metabolomics revealed 21 downregulated and 17 upregulated metabolites between TI phenotypes. Correlation analysis showed that the genus cc115 and 10 plasma metabolites were positively correlated with aggressive behavior, whereas 8 metabolites were negatively correlated. LTI broilers have higher plasma corticosterone content and more intense aggressive behavior than STI broilers. The distinct behavioral and physiological profiles observed in broilers with different TI phenotypes are strongly correlated with their specific gut microbiota and differential plasma metabolite profiles. The identified gut microbial signatures serve as key biomarkers for regulating aggressive behavior in broilers, while the differential plasma metabolites represent potential early indicators for detecting stress and behavioral issues in poultry farming.

Prenatal maternal life adversity impacts on learning and memory in offspring: implication to transgenerational epigenetic inheritance

Maternal stress exposure during pregnancy is known to affect offspring behavior, including learning and memory. We hypothesized that maternal stress-induced changes transmit this effect through maternal line mediated transgenerational epigenetic inheritance. To test our hypothesis, pregnant rats (F0) were undisturbed (Control, Ctrl)/exposed to social stress during gestational days (GD) 16-18 (PMS)/exposed to social stress and treated with oxytocin during GD-16 to 18 (PMS+OXT). Subsequently, F1 female offspring from Ctrl, PMS, and PMS+OXT were mated with Ctrl F1 males to examine maternal line mediated transgenerational impacts. Female animals (F1 and F2) were subjected to behavioral test and the levels of global H3K4me2/H3K4me3 methylation, methylation in the CRH promoter, expression of Crh, Crh receptors (Crhr1, Crhr2), and BDNF were determined. It was found that prenatal maternal stress (PMS) reduced reference and working memory in F1 and F2 offspring, increased global and specific H3K4me2, H3K4me3 methylation in the CRH promoter, expression of Crh, Crh receptors, and corticosterone (CORT), and down-regulated the expression of pro-and mature BDNF by differentially regulating Bdnf transcripts III, IV and VI in the amygdala. Oxytocin exposure reduced PMS-induced global and specific H3K4me2/3 changes, which repressed the expression of Crh, Crh receptors, reduced CORT levels, up-regulated the expression of pro-BDNF and mature BDNF, and improved memory in F1 and F2 offspring. Collectively, our study revealed that PMS reduced reference and working memory performance in F1 and F2 offspring through maternal line transgenerational inheritance of H3K4me2, H3K4me3 methylation, and associated mechanisms that regulate BDNF expression and synaptic plasticity.

Chronic social instability stress differentially affects the behavior and the transcriptome of the anterodorsal bed nucleus of the stria terminalis between male and female mice

Stress can be broken down into systemic and processive stressors with processive stressors requiring higher limbic processing. These are also often called social stressors as they require an understanding of social dynamics as opposed to physical based stressors. This differing of processing necessitates we study both phenomena. Additionally, sex is an important aspect of stress research as men and women show differing responses to stress and mood disorder development. To study this, we used a chronic social instability stress (CSIS) paradigm to stress male and female mice. This paradigm is approximately 7-weeks long and involves changing the cage mates of a mouse every 3 days so stable social dynamics cannot form. Afterwards, one cohort was used for avoidance behavior testing using the open field test, the elevated plus maze, the light/dark box emergence test, and the novelty suppressed feeding test. A second cohort was used for bulk RNA-Sequencing of the anterodorsal bed nucleus of the stria terminalis which is a limbic structure known to be related to chronic stress signaling. In the behavior assays, CSIS caused the females to be less avoidant, while the males became more avoidant. Additionally, we found that a low estrogen state in the females caused them to be less avoidant than in a high estrogen state. In the transcriptome, we found major differences between the males and females with the males expressing more genes related to transcription whereas the females expressed more genes related to synaptic transmission. We also found that the transcriptome in the males is more sensitive to the stress than the females. In summary, we have found how social stress is differentially regulated between males and females and how this may be related to the development of stress-related behavioral changes.

Direct Modulation of CRH Nerve Terminal Function by Noradrenaline and Corticosterone

Nerve terminals are the final point of regulation before neurosecretion. As such, neuromodulators acting on nerve terminals can exert significant influence on neural signaling. Hypothalamic corticotropin-releasing hormone (CRH) neurons send axonal projections to the median eminence where CRH is secreted to stimulate the hypothalamic-pituitary-adrenal (HPA) axis. Noradrenaline and corticosterone are two of the most important neuromodulators of HPA axis function; noradrenaline excites CRH neurons and corticosterone inhibits CRH neurons by negative feedback. Here, we used GCaMP6f Ca2+ imaging and measurement of nerve terminal CRH secretion using sniffer cells to determine whether these neuromodulators act directly on CRH nerve terminals in male mice. Contrary to expectations, noradrenaline inhibited action potential-dependent Ca2+ elevations in CRH nerve terminals and suppressed evoked CRH secretion. This inhibitory effect was blocked by α2-adrenoreceptor antagonism. Corticosterone also suppressed evoked CRH peptide secretion from nerve terminals, independent of action potential-dependent Ca2+ levels. This inhibition was prevented by the glucocorticoid receptor antagonist, RU486, and indicates that CRH nerve terminals may be a site of fast glucocorticoid negative feedback. Together these findings establish median eminence nerve terminals as a key site for regulation of the HPA axis.

The neurobiology of parenting and infant-evoked aggression

Parenting behavior comprises a variety of adult-infant and adult-adult interactions across multiple timescales. The state transition from nonparent to parent requires an extensive reorganization of individual priorities and physiology and is facilitated by combinatorial hormone action on specific cell types that are integrated throughout interconnected and brainwide neuronal circuits. In this review, we take a comprehensive approach to integrate historical and current literature on each of these topics across multiple species, with a focus on rodents. New and emerging molecular, circuit-based, and computational technologies have recently been used to address outstanding gaps in our current framework of knowledge on infant-directed behavior. This work is raising fundamental questions about the interplay between instinctive and learned components of parenting and the mutual regulation of affiliative versus agonistic infant-directed behaviors in health and disease. Whenever possible, we point to how these technologies have helped gain novel insights and opened new avenues of research into the neurobiology of parenting. We hope this review will serve as an introduction for those new to the field, a comprehensive resource for those already studying parenting, and a guidepost for designing future studies.

Glutamatergic neurons of basolateral amygdala mediate increased exploratory behaviors produced by mildly chronic restraint stress in adolescent mice

In response to stressors, individuals manifest varied behavioral responses directed toward satisfying physiological survival needs. Although the enduring effects of adolescent stress on both humans and animals are well-documented, the underlying mechanisms remain insufficiently elucidated. Utilizing immunofluorescence, viral injections, and brain slice electrophysiological recordings, we have delineated that heightened excitability among glutamatergic neurons in the basolateral amygdala (BLA) is responsible for inducing heightened exploratory behaviors in adolescent mice subjected to mild, chronic restraint stress. Activation of BLA glutamatergic neurons through chemogenetics increases exploratory behaviors in emotional assessments, whereas inhibition of these neurons diminishes exploratory behaviors in measures such as the open field and elevated plus maze test. Furthermore, an upregulation of glutamate receptor expression and a concomitant downregulation of GABA receptor expression in BLA glutamatergic neurons have been associated with enhanced exploratory behaviors, validated through in vivo receptor antagonists. These findings unveil the protective role of mild stress exposure during adolescence against adversity, providing novel insights for addressing stressful events.

Early-life challenge enhances cortisol regulation in zebrafish larvae

The hypothalamic-pituitary-adrenal (HPA) axis in mammals and the hypothalamic-pituitary-interrenal (HPI) axis in fish are open systems that adapt to the environment during development. Little is known about how this adaptation begins and regulates early stress responses. We used larval zebrafish to examine the impact of prolonged forced swimming at 5 days post-fertilization (dpf), termed early-life challenge (ELC), on cortisol responses, neuropeptide expression in the nucleus preopticus (NPO), and gene transcript levels. At 6 dpf, ELC-exposed larvae showed normal baseline cortisol but reduced reactivity to an initial stressor. Conversely, they showed increased reactivity to a second stressor within the 30-min refractory period, when cortisol responses are typically suppressed. ELC larvae had fewer corticotropin-releasing hormone (crh), arginine vasopressin (avp), and oxytocin (oxt)-positive cells in the NPO, with reduced crh and avp co-expression. Gene expression analysis revealed upregulation of genes related to cortisol metabolism (hsd11b2, cyp11c1), steroidogenesis (star), and stress modulation (crh, avp, oxt). These results suggest that early environmental challenge initiates adaptive plasticity in the HPI axis, tuning cortisol regulation to balance responsiveness and protection during repeated stress. Future studies should explore the broader physiological effects of prolonged forced swimming and its long-term impact on cortisol regulation and stress-related circuits.

Defects of parvalbumin-positive interneurons are implicated in psychiatric disorders

Psychiatric disorders are a common cause of severe long-term disability and socioeconomic burden worldwide. Although our understanding of these disorders has advanced substantially over the last few years, little has changed the standards of care for these illnesses. Fast-spiking parvalbumin-positive interneurons (PVIs), a subpopulation of gamma-aminobutyric acid (GABA)ergic interneurons, are widely distributed in the hippocampus and have been reported to play an important role in various mental disorders. However, the mechanisms underlying the regulation of the molecular networks relevant to depression and schizophrenia (SCZ) are unknown. Here, we discuss the functions of PVIs in psychiatric disorders, including depression and SCZ. After reviewing several studies, we concluded that dysfunction in PVIs could cause depression-like behavior, as well as cognitive categories in SCZ, which might be mediated in large part by greater synaptic variability. In summary, this scientific review aims to discuss the current knowledge regarding the function of PVIs in depression and SCZ. Moreover, we highlight the importance of neurogenesis and synaptic plasticity in the pathogenesis of depression and SCZ, which seem to be mediated by PVIs activity. These findings provide a better understanding of the role of PVIs in psychiatric disorders.

Evaluation of the c-Fos expression in the hippocampus after fatigue caused by one session of endurance exercise in pre-pubertal and adult rats

PURPOSE

Central fatigue plays an important role in reducing endurance exercise activity during brain development. c-Fos gene expression in the hippocampus was examined as an indicator of neuronal activation after exhaustion.

METHODS

Eighteen pre-pubertal male rats at four weeks old and 18 adult rats at eight weeks were randomly divided into three groups: Control (C), Constant time exercise (CTEx), Endurance Exercise until Exhaustion (ExhEx), which started at two minutes and ended in 20 min, the main swimming test was performed with a weight equal to 5% of the bodyweight attached to the rats' tail as a single session in experimental groups and was recorded at the end of their time, while to evaluate the force loss, the Grip strength was measured before and after the activity. The brain activation rate was examined by c-Fos gene expression and Nissl staining in CA3 and dentate gyrus (DG) in the hippocampus of all groups.

RESULTS

Power grip and Nissl positive neurons in CA3 and DG have been significantly higher in pre-pubertal rats than in adults, both in the CTEx group (p = 0.04) and in the ExhEx group (p < 0.001). Also, real-time exhaustion in the pre-pubertal group was significantly longer than in adults. c-Fos gene expression was significantly reduced in adults' hippocampus in comparison to preadolescence (p < 0.01) and control (p < 0.001).

CONCLUSION

These findings clarified that increased strength and longer fatigue in pre-puberal rats may lead to c-Fos gene expression and decreased neurons in the hippocampus. Perhaps this is a protective effect to suppress stress hormones.

Involvement of D1 dopamine receptor in the nucleus of the solitary tract of rats in stress-induced hypertension and exercise

OBJECTIVE

Chronic stress can cause hypertension, whereas daily exercise promotes healthy well being through destressing. Although the nucleus of the solitary tract (NTS) is involved in the development of hypertension, the molecular and physiological mechanisms of stress and exercise remain unclear. In this study, we tested whether gene expression in the NTS is altered by stress and daily exercise and whether this is involved in cardiovascular regulation.

METHODS

We have performed RT 2 Profiler PCR arrays targeting a panel of neurotransmitter receptor genes in the NTS of Wistar rats subjected to chronic restraint stress (1 h a day over 3 weeks) with or without voluntary wheel exercise. We also performed immunohistochemistry to determine whether the identified molecules were expressed at the protein level. Additionally, microinjection studies in anesthetized rats were performed to examine whether validated molecules exhibit physiological roles in cardiovascular regulation of the NTS.

RESULTS

We observed that blood pressure was significantly increased by stress and the increase was suppressed by exercise. Using PCR analysis, we determined that the expression levels of four genes in the NTS, including the dopamine receptor D1 gene ( Drd1 ), were significantly affected by stress and suppressed by exercise. We also examined dopamine D1 receptor (D1R) expression in NTS neurons and found significantly greater expression in the stressed than nonstressed animals. Furthermore, the microinjection of a D1R agonist into the NTS in anesthetized rats induced hypotensive effects.

CONCLUSION

These results suggest that NTS D1R plays a role in the counteracting processes of stress-induced hypertension.

Microglia, circadian rhythm and lifestyle factors

Microglia, a vital homeostasis-keeper of the central nervous system, perform critical functions such as synaptic pruning, clearance of cellular debris, and participation in neuroinflammatory processes. Recent research has shown that microglia exhibit strong circadian rhythms that not only actively regulate their own immune activity, but also affect neuronal function. Disruptions of the circadian clock have been linked to a higher risk of developing a variety of diseases. In this article we will provide an overview of how lifestyle factors impact microglial function, with a focus on disruptions caused by irregular sleep-wake patterns, reduced physical activity, and eating at the wrong time-of-day. We will also discuss the potential connection between these lifestyle factors, disrupted circadian rhythms, and the role of microglia in keeping brain health. This article is part of the Special Issue on "Microglia".

Modulating reward and aversion: Insights into addiction from the paraventricular nucleus

BACKGROUND

Drug addiction, characterized by compulsive drug use and high relapse rates, arises from complex interactions between reward and aversion systems in the brain. The paraventricular nucleus (PVN), located in the anterior hypothalamus, serves as a neuroendocrine center and is a key component of the hypothalamic-pituitary-adrenal axis.

OBJECTIVE

This review aimed to explore how the PVN impacts reward and aversion in drug addiction through stress responses and emotional regulation and to evaluate the potential of PVN as a therapeutic target for drug addiction.

METHODS

We review the current literature, focusing on three main neuron types in the PVN-corticotropin-releasing factor, oxytocin, and arginine vasopressin neurons-as well as other related neurons, to understand their roles in modulating addiction.

RESULTS

Existing studies highlight the PVN as a key mediator in addiction, playing a dual role in reward and aversion systems. These findings are crucial for understanding addiction mechanisms and developing targeted therapies.

CONCLUSION

The role of PVN in stress response and emotional regulation suggests its potential as a therapeutic target in drug addiction, offering new insights for addiction treatment.

Differential increase of hippocampal subfield volume after socio-affective mental training relates to reductions in diurnal cortisol

The hippocampus is a central modulator of the HPA-axis, impacting the regulation of stress on brain structure, function, and behavior. The current study assessed whether three different types of 3 months mental Training Modules geared towards nurturing (a) attention-based mindfulness, (b) socio-affective, or (c) socio-cognitive skills may impact hippocampal organization by reducing stress. We evaluated mental training-induced changes in hippocampal subfield volume and intrinsic functional connectivity, by combining longitudinal structural and resting-state fMRI connectivity analysis in 332 healthy adults. We related these changes to changes in diurnal and chronic cortisol levels. We observed increases in bilateral cornu ammonis volume (CA1-3) following the 3 months compassion-based module targeting socio-affective skills (Affect module), as compared to socio-cognitive skills (Perspective module) or a waitlist cohort with no training intervention. Structural changes were paralleled by relative increases in functional connectivity of CA1-3 when fostering socio-affective as compared to socio-cognitive skills. Furthermore, training-induced changes in CA1-3 structure and function consistently correlated with reductions in cortisol output. Notably, using a multivariate approach, we found that other subfields that did not show group-level changes also contributed to changes in cortisol levels. Overall, we provide a link between a socio-emotional behavioural intervention, changes in hippocampal subfield structure and function, and reductions in cortisol in healthy adults.

Glucocorticoid signaling mediates stress-induced migraine-like behaviors in a preclinical mouse model

BACKGROUND

Stress is one of the most common precipitating factors in migraine and is identified as a trigger in nearly 70% of patients. Responses to stress include release of glucocorticoids as an adaptive mechanism, but this may also contribute to migraine attacks. Here, we investigated the role of glucocorticoids on stress-induced migraine-like behaviors.

METHODS

We have shown previously that repeated stress in mice evokes migraine-like behavioral responses and priming to a nitric oxide donor. Metyrapone, mifepristone, and corticosterone (CORT) were used to investigate whether CORT contributes to the stress-induced effects. Facial mechanical hypersensitivity was evaluated by von Frey testing and grimace scoring assessed the presence of non-evoked pain. We also measured serum CORT levels in control, stress, and daily CORT injected groups of both male and female mice.

RESULTS

Metyrapone blocked stress-induced responses and priming in male and female mice. However, repeated CORT injections in the absence of stress only led to migraine-like behaviors in females. Both female and male mice showed similar patterns of serum CORT in response to stress or exogenous administration. Finally, administration of mifepristone, the glucocorticoid receptor antagonist, prior to each stress session blocked stress-induced behavioral responses in male and female mice.

CONCLUSIONS

These findings demonstrate that while CORT synthesis and receptor activation is necessary for the behavioral responses triggered by repeated stress, it is only sufficient in females. Better understanding of how glucocorticoids contribute to migraine may lead to new therapeutic opportunities.

A Hypothalamic Perspective of Human Socioemotional Behavior

Historical evidence from stimulation and lesion studies in animals and humans demonstrated a close association between the hypothalamus and typical and atypical socioemotional behavior. A central hypothalamic contribution to regulation of socioemotional responses was also provided indirectly by studies on oxytocin and arginine vasopressin. However, a limited number of studies have so far directly investigated the contribution of the hypothalamus in human socioemotional behavior. To reconsider the functional role of the evolutionarily conserved hypothalamic region in regulating human social behavior, here I provide a synthesis of neuroimaging investigations showing that the hypothalamus is involved in multiple and diverse facets of human socioemotional behavior through widespread functional interactions with other cortical and subcortical regions. These neuroimaging findings are then integrated with recent optogenetics studies in animals demonstrating that the hypothalamus plays a more active role in eliciting socioemotional responses and is not simply a downstream effector of higher-level brain systems. Building on the aforementioned evidence, the hypothalamus is argued to substantially contribute to a continuum of human socioemotional behaviors promoting survival and preservation of the species that extends from exploratory and approaching responses facilitating social bonding to aggressive and avoidance responses aimed to protect and defend formed relationships.

A novel animal paradigm of long-term, stress-induced hippocampal atrophy

Long-term hippocampal atrophy is a key feature of major depression. In contrast, in rodents subjected to chronic stress there is reversibly decreased hippocampal volume. We show that exposure to seven days of restraint stress alone or with antidepressant treatment combined with a persistent high-fat diet environment lasting 165 days resulted in long-term, stress-induced hippocampal volume reduction in rats, better reflecting the hippocampal shrinkage that is well documented in patients with major depressive disorder.

SNX27: A trans-species cognitive modulator with implications for anxiety and stress susceptibility

Sorting Nexin 27 (SNX27) is a brain-enriched endosome-associated cargo adaptor that shapes excitatory control, being relevant for cognitive and reward processing, and for several neurological conditions. Despite this, SNX27's role in the nervous system remains poorly explored. To further understand SNX27 function, we performed an extensive behavioral characterization comprising motor, cognitive and emotional dimensions of SNX27+/- mice. Furthermore, attending on the recently described association between SNX27 function and cellular stress signaling mechanisms in vitro, we explored SNX27-stress interplay using a Caenorhabditis elegans Δsnx-27 mutant and wild-type (WT) rodents after stress exposure. SNX27+/- mice, as C. elegans Δsnx-27 mutants, present cognitive impairments, highlighting a conserved role for SNX27 in cognitive modulation across species. Interestingly, SNX27 downmodulation leads to anxiety-like behavior in mice evaluated in the Elevated Plus Maze (EPM). This anxious phenotype is associated with increased dendritic complexity of the bed nucleus of the stria terminalis (BNST) neurons, and increased complexity of the basolateral amygdala (BLA) pyramidal neurons. These findings highlight the still unknown role of SNX27 in anxiety regulation. Moreover, we uncovered a direct link between SNX27 dysfunction and stress susceptibility in C. elegans and found that stress-exposed rodents display decreased SNX27 levels in stress-susceptible brain regions. Altogether, we provided new insights on SNX27's relevance in anxiety-related behaviors and neuronal structure in stress-associated brain regions.

A high salt intake in early life affects stress-coping response in males but not in female rats

Eating diets high in salt has been associated with alterations in the immune system and the potential development of neuropsychiatric disorders. This area of research shows promise, but there is currently a limited amount of research on this topic. The present study investigated whether a high salt diet (HSD) affects anhedonia and stress-coping response behaviors in young male and female Wistar rats. In this study, male and female Wistar rats were fed an HSD (8 % NaCl w/w) from weaning to post-natal day (PND) 64. From PND 60 to 64, the rats underwent a spontaneous locomotor activity test (SLA), sucrose splash test (SST), sucrose preference test (SPT), and forced swim test (FST), followed by euthanasia at PND 65. Male and female rats consuming the HSD exhibited an increase in water intake compared to the corresponding control diet (CD) groups. Male rats had lower body weight despite having similar food intakes compared to the CD group. Male rats displayed an active stress-coping behavior in the FST, characterized by increased mobility. Additionally, HSD-fed males exhibited a greater preference for sucrose solution in the SPT. However, no effect of diet and sex were detected in the SST and the SLA, and hypothalamic levels of leptin and ghrelin receptors. On the other hand, female rats were less susceptible to the experimental conditions applied in this protocol than males.

C. Social Context in Stress and Autism: Comparing Physiological Profiles Across Two Social Paradigms in Youth with and without Autism Spectrum Disorder

Background

The social world is often stressful for individuals with autism spectrum disorder (ASD). Research shows youth with ASD demonstrate physiological hyperreactivity to some social stressors (e.g., interaction) but not others (e.g., evaluation); therefore, this study examined diagnosis (ASD or typical development (TD)), social context, perceived anxiety, and physiological responsivity across multiple stress systems; namely, the hypothalamic pituitary adrenal (HPA) axis and autonomic nervous system (ANS).

Method

This study examined 244 ten-to-thirteen-year-olds with ASD (N = 140) or TD (N = 104). Physiological responses, measured by salivary cortisol, heart rate (HR), and respiratory sinus arrhythmia (RSA), were assessed before and after a social evaluative threat paradigm (Trier Social Stress Test; TSST) and social interaction (Trier Social Stress Test- Friendly; TSST-F). Mediation models examined the relationships between anxiety, diagnosis, and physiology.

Results

Significant three-way interactions were observed for cortisol (p=0.007) and HR (p=0.002), suggesting diagnostic groups respond differently across context and time points. There was no significant interaction for RSA (p=0.149), although ASD youth had significantly lower RSA overall (p=0.038). State and trait anxiety did not mediate the relationship between diagnosis and physiology (all p>0.05).

Conclusions

Findings emphasize the critical role of context and a multisystem approach in examination of physiological social stress in youth with ASD. Results provide a foundation to elucidate unique response patterns across physiological systems to more precisely identify those with heightened physiological arousal across social contexts. It is proposed that future identification of subtypes may ultimately inform approaches for enhancing social engagement.

Premotor projections from the locus coeruleus and periaqueductal grey are altered in two rat models with inborn differences in emotional behavior

Emotionally motivated behaviors rely on the coordinated activity of descending neural circuits involved in motor and autonomic functions. Using a pseudorabies (PRV) tract-tracing approach in typically behaving rats, our group previously identified descending premotor, presympathetic, and dual-labeled premotor-presympathetic populations throughout the central rostral-caudal axis. The premotor-presympathetic populations are thought to integrate somatomotor and sympathetic activity. To determine whether these circuits are dysregulated in subjects with altered emotional regulation, subsequent neuroanatomical analyses were performed in male subjects of two distinct genetic models relevant to clinical depression and anxiety: the Wistar Kyoto (WKY) rat and selectively bred Low Novelty Responder (bLR) rat. The present study explored alterations in premotor efferents from locus coeruleus (LC) and subdivisions of the periaqueductal grey (PAG), two areas involved in emotionally motivated behaviors. Compared to Sprague Dawley rats, WKY rats had significantly fewer premotor projections to hindlimb skeletal muscle from the LC and from the dorsomedial (DMPAG), lateral (LPAG), and ventrolateral (VLPAG) subdivisions of PAG. Relative to selectively bred High Novelty Responder (bHR) rats, bLR rats had significantly fewer premotor efferents from LC and dorsolateral PAG (DLPAG). Cumulatively, these results demonstrate that somatomotor circuitry in several brain areas involved in responses to stress and emotional stimuli are altered in rat models with depression-relevant phenotypes. These somatomotor circuit differences could be implicated in motor-related impairments in clinically depressed patients.

Patterns of neural activity in response to threatening faces are predictive of autistic traits: modulatory effects of oxytocin receptor genotype

Autistic individuals generally demonstrate impaired emotion recognition but it is unclear whether effects are emotion-specific or influenced by oxytocin receptor (OXTR) genotype. Here we implemented a dimensional approach using an implicit emotion recognition task together with functional MRI in a large cohort of neurotypical adult participants (N = 255, male = 131, aged 17-29 years) to establish associations between autistic traits and neural and behavioral responses to specific face emotions, together with modulatory effects of OXTR genotype. A searchlight-based multivariate pattern analysis (MVPA) revealed an extensive network of frontal, basal ganglia, cingulate and limbic regions exhibiting significant predictability for autistic traits from patterns of responses to angry relative to neutral expression faces. Functional connectivity analyses revealed a genotype interaction (OXTR SNPs rs2254298, rs2268491) for coupling between the orbitofrontal cortex and mid-cingulate during angry expression processing, with a negative association between coupling and autistic traits in the risk-allele group and a positive one in the non-risk allele group. Overall, results indicate extensive emotion-specific associations primarily between patterns of neural responses to angry faces and autistic traits in regions processing motivation, reward and salience but not in early visual processing. Functional connections between these identified regions were not only associated with autistic traits but also influenced by OXTR genotype. Thus, altered patterns of neural responses to threatening faces may be a potential biomarker for autistic symptoms although modulatory influences of OXTR genotype need to be taken into account.

Genetic and environmental influences on alpha amylase stress reactivity and shared genetic covariation with cortisol

Salivary alpha amylase (sAA) is a common measure of stress reactivity, primarily reflecting sympathetic nervous system activity. Salivary cortisol is also a reliable, frequently used biomarker of stress and reflects the hypothalamic-pituitary-adrenal (HPA) axis response. This study examined heritability across varying metrics of sAA in response to a social evaluative stressor, the Trier Social Stress Test (TSST). The goal of this study was to estimate genetic and environmental influences on measurements of sAA stress reactivity. Moreover, we evaluated the shared genetic covariation between sAA and cortisol. Participants included twins aged 15-20 years (54% female). We measured alpha amylase and cortisol reactivity to the TSST via serial salivary cortisol samples collected pre- and post-TSST. Modest to moderate heritability estimates (11-64%) were observed across measures purported to capture alpha amylase stress reactivity (peak, area under the curve, baseline-to-peak change). Findings also indicate that sAA baseline and peak are primarily influenced by a shared genetic factor. There was no evidence of shared genetic influences between sAA and cortisol. These findings suggest the genetic control of the HPA and Sympathetic Adreno-Medullar axis are genetically independent of one another despite both playing a role in response to stressors.

Validity of mental and physical stress models

Different stress models are employed to enhance our understanding of the underlying mechanisms and explore potential interventions. However, the utility of these models remains a critical concern, as their validities may be limited by the complexity of stress processes. Literature review revealed that both mental and physical stress models possess reasonable construct and criterion validities, respectively reflected in psychometrically assessed stress ratings and in activation of the sympathoadrenal system and the hypothalamic-pituitary-adrenal axis. The findings are less robust, though, in the pharmacological perturbations' domain, including such agents as adenosine or dobutamine. Likewise, stress models' convergent- and discriminant validity vary depending on the stressors' nature. Stress models share similarities, but also have important differences regarding their validities. Specific traits defined by the nature of the stressor stimulus should be taken into consideration when selecting stress models. Doing so can personalize prevention and treatment of stress-related antecedents, its acute processing, and chronic sequelae. Further work is warranted to refine stress models' validity and customize them so they commensurate diverse populations and circumstances.

Manual segmentation of the paraventricular nucleus of the hypothalamus and the dorsal and ventral bed nucleus of stria terminalis using multimodal 7 Tesla structural MRI: probabilistic atlases for a stress-control triad

The paraventricular nucleus of the hypothalamus (PVN) is uniquely capable of proximal control over autonomic and neuroendocrine stress responses, and the bed nucleus of the stria terminalis (BNST) directly modulates PVN function, as well as playing an important role in stress control itself. The dorsal BNST (dBNST) is predominantly preautonomic, while the ventral BNST (vBNST) is predominantly viscerosensory, receiving dense noradrenergic signaling. Distinguishing the dBNST and vBNST, along with the PVN, may facilitate our understanding of dynamic interactions among these regions. T1-weighted MPRAGE and high resolution gradient echo (GRE) modalities were acquired at 7T. GRE was coregistered to MPRAGE and segmentations were performed in MRIcroGL based on their Atlas of the Human Brain depictions. The dBNST, vBNST and PVN were manually segmented in 25 participants; 10 images were rated by 2 raters. These segmentations were normalized and probabilistic atlases for each region were generated in MNI space, now available as resources for future research. We found moderate-high inter-rater reliability [n = 10; Mean Dice (SD); PVN = 0.69 (0.04); dBNST = 0.77 (0.04); vBNST = 0.62 (0.04)]. Probabilistic atlases were reverse normalized into native space for six additional participants that were segmented but not included in the original 25. We also found moderate to moderate-high reliability between the probabilistic atlases and manual segmentations [n = 6; Mean Dice (SD); PVN = 0.55 (0.12); dBNST = 0.60 (0.10); vBNST = 0.47 (0.12 SD)]. By isolating these hypothalamic and BNST subregions using ultra-high field MRI modalities, more specific delineations of these regions can facilitate greater understanding of mechanisms underlying stress-related function and psychopathology.

Role of estrogen in treatment of female depression

Depression is a neurological disorder that profoundly affects human physical and mental health, resulting in various changes in the central nervous system. Despite several prominent hypotheses, such as the monoaminergic theory, hypothalamic-pituitary-adrenal (HPA) axis theory, neuroinflammation, and neuroplasticity, the current understanding of depression's pathogenesis remains incomplete. Importantly, depression is a gender-dimorphic disorder, with women exhibiting higher incidence rates than men. Given estrogen's pivotal role in the menstrual cycle, it is reasonable to postulate that its fluctuating levels could contribute to the pathogenesis of depression. Estrogen acts by binding to a diversity of receptors, which are widely distributed in the central nervous system. An abundance of research has established that estrogen and its receptors play a crucial role in depression, spanning pathogenesis and treatment. In this comprehensive review, we provide an in-depth analysis of the fundamental role of estrogen and its receptors in depression, with a focus on neuroinflammation, neuroendocrinology, and neuroplasticity. Furthermore, we discuss potential mechanisms underlying the therapeutic effects of estrogen in the treatment of depression, which may pave the way for new antidepressant drug development and alternative treatment options.

Capturing wild animal welfare: a physiological perspective

Affective states, such as emotions, are presumably widespread across the animal kingdom because of the adaptive advantages they are supposed to confer. However, the study of the affective states of animals has thus far been largely restricted to enhancing the welfare of animals managed by humans in non-natural contexts. Given the diversity of wild animals and the variable conditions they can experience, extending studies on animal affective states to the natural conditions that most animals experience will allow us to broaden and deepen our general understanding of animal welfare. Yet, this same diversity makes examining animal welfare in the wild highly challenging. There is therefore a need for unifying theoretical frameworks and methodological approaches that can guide researchers keen to engage in this promising research area. The aim of this article is to help advance this important research area by highlighting the central relationship between physiology and animal welfare and rectify its apparent oversight, as revealed by the current scientific literature on wild animals. Moreover, this article emphasises the advantages of including physiological markers to assess animal welfare in the wild (e.g. objectivity, comparability, condition range, temporality), as well as their concomitant limitations (e.g. only access to peripheral physiological markers with complex relationships with affective states). Best-practice recommendations (e.g. replication and multifactorial approaches) are also provided to allow physiological markers to be used most effectively and appropriately when assessing the welfare of animals in their natural habitat. This review seeks to provide the foundation for a new and distinct research area with a vast theoretical and applied potential: wild animal welfare physiology.

Effect of propranolol on temporomandibular joint pain in repeatedly stressed rats

Stress substantially increases the risk of developing painful temporomandibular disorders (TMDs) by influencing the release of endogenous catecholamines. Propranolol, an antagonist of β-adrenergic receptors, has shown potential in alleviating TMD-associated pain, particularly when the level of catecholamines is elevated. The aim of this study was to explore whether intra-articular propranolol administration is effective in diminishing temporomandibular joint (TMJ) pain during repeated stress situations. Additionally, we investigated the effect of repeated stress on the expression of genes encoding β-adrenoceptors in the trigeminal ganglion. In the present study, rats were exposed to a stress protocol induced by sound, then to the administration of formalin in the TMJ (to elicit a nociceptive response), followed immediately afterward by different doses of propranolol, after which the analgesic response to propranolol was evaluated. We also assessed the levels of beta-1 and beta-2 adrenergic receptor mRNAs (Adrb1 and Adrb2, respectively) using reverse transcription-quantitative PCR (RT-qPCR). Our findings revealed that propranolol administration reduces formalin-induced TMJ nociception more effectively in stressed rats than in non-stressed rats. Furthermore, repeated stress decreases the expression of the Adrb2 gene within the trigeminal ganglion. The findings of this study are noteworthy as they suggest that individuals with a chronic stress history might find potential benefits from β-blockers in TMD treatment.

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

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

Regulation of stress-induced sleep fragmentation by preoptic glutamatergic neurons

Sleep disturbances are detrimental to our behavioral and emotional well-being. Stressful events disrupt sleep, in particular by inducing brief awakenings (microarousals, MAs), resulting in sleep fragmentation. The preoptic area of the hypothalamus (POA) is crucial for sleep control. However, how POA neurons contribute to the regulation of MAs and thereby impact sleep quality is unknown. Using fiber photometry in mice, we examine the activity of genetically defined POA subpopulations during sleep. We find that POA glutamatergic neurons are rhythmically activated in synchrony with an infraslow rhythm in the spindle band of the electroencephalogram during non-rapid eye movement sleep (NREMs) and are transiently activated during MAs. Optogenetic stimulation of these neurons promotes MAs and wakefulness. Exposure to acute social defeat stress fragments NREMs and significantly increases the number of transients in the calcium activity of POA glutamatergic neurons during NREMs. By reducing MAs, optogenetic inhibition during spontaneous sleep and after stress consolidates NREMs. Monosynaptically restricted rabies tracing reveals that POA glutamatergic neurons are innervated by brain regions regulating stress and sleep. In particular, presynaptic glutamatergic neurons in the lateral hypothalamus become activated after stress, and stimulating their projections to the POA promotes MAs and wakefulness. Our findings uncover a novel circuit mechanism by which POA excitatory neurons regulate sleep quality after stress.

Optogenetic recruitment of hypothalamic corticotrophin-releasing-hormone (CRH) neurons reduces motivational drive

Impaired motivational drive is a key feature of depression. Chronic stress is a known antecedent to the development of depression in humans and depressive-like states in animals. Whilst there is a clear relationship between stress and motivational drive, the mechanisms underpinning this association remain unclear. One hypothesis is that the endocrine system, via corticotropin-releasing hormone (CRH) in the paraventricular nucleus of the hypothalamus (PVN; PVNCRH), initiates a hormonal cascade resulting in glucocorticoid release, and that excessive glucocorticoids change brain circuit function to produce depression-related symptoms. Another mostly unexplored hypothesis is that the direct activity of PVNCRH neurons and their input to other stress- and reward-related brain regions drives these behaviors. To further understand the direct involvement of PVNCRH neurons in motivation, we used optogenetic stimulation to activate these neurons 1 h/day for 5 consecutive days and showed increased acute stress-related behaviors and long-lasting deficits in the motivational drive for sucrose. This was associated with increased Fos-protein expression in the lateral hypothalamus (LH). Direct stimulation of the PVNCRH inputs in the LH produced a similar pattern of effects on sucrose motivation. Together, these data suggest that PVNCRH neuronal activity may be directly responsible for changes in motivational drive and that these behavioral changes may, in part, be driven by PVNCRH synaptic projections to the LH.

Adolescent high fat diet alters the transcriptional response of microglia in the prefrontal cortex in response to stressors in both male and female mice

Both obesity and high fat diets (HFD) have been associated with an increase in inflammatory gene expression within the brain. Microglia play an important role in early cortical development and may be responsive to HFD, particularly during sensitive windows, such as adolescence. We hypothesized that HFD during adolescence would increase proinflammatory gene expression in microglia at baseline and potentiate the microglial stress response. Two stressors were examined, a physiological stressor [lipopolysaccharide (LPS), IP] and a psychological stressor [15 min restraint (RST)]. From 3 to 7 weeks of age, male and female mice were fed standard control diet (SC, 20% energy from fat) or HFD (60% energy from fat). On P49, 1 h before sacrifice, mice were randomly assigned to either stressor exposure or control conditions. Microglia from the frontal cortex were enriched using a Percoll density gradient and isolated via fluorescence-activated cell sorting (FACS), followed by RNA expression analysis of 30 genes (27 target genes, three housekeeping genes) using Fluidigm, a medium throughput qPCR platform. We found that adolescent HFD induced sex-specific transcriptional response in cortical microglia, both at baseline and in response to a stressor. Contrary to our hypothesis, adolescent HFD did not potentiate the transcriptional response to stressors in males, but rather in some cases, resulted in a blunted or absent response to the stressor. This was most apparent in males treated with LPS. However, in females, potentiation of the LPS response was observed for select proinflammatory genes, including Tnfa and Socs3. Further, HFD increased the expression of Itgam, Ikbkb, and Apoe in cortical microglia of both sexes, while adrenergic receptor expression (Adrb1 and Adra2a) was changed in response to stressor exposure with no effect of diet. These data identify classes of genes that are uniquely affected by adolescent exposure to HFD and different stressor modalities in males and females.

Differential c-Fos Response in Neurocircuits Activated by Repeated Predator Stress in Male and Female C57BL/6J Mice with Stress Sensitive or Resilient Alcohol Intake Phenotypes

Comorbidity of post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) worsens the prognosis for each of these individual disorders. The current study aimed to identify neurocircuits potentially involved in regulation of PTSD-AUD comorbidity by mapping expression of c-Fos in male and female C57BL/6J mice following repeated predator stress (PS), modeled by exposure to dirty rat bedding. In experiment 1, the levels of c-Fos in the paraventricular nucleus of the hypothalamus (PVH) and the nucleus accumbens shell were higher after the second PS vs the first PS, indicating a sensitized response to this stressor. Additional brain regions showed varied sex-dependent and independent regulation by the two consecutive PS exposures. In experiment 2, mice that increased voluntary alcohol consumption following four exposures to PS (Sensitive subgroup) showed higher c-Fos induction in the PVH, piriform cortex and ventromedial hypothalamus than mice that decreased consumption following these exposures (Resilient subgroup). In contrast to these brain regions, c-Fos was higher in the anterior olfactory nucleus of Resilient vs Sensitive mice. Taken together, these data demonstrate that repeated PS exposure and voluntary alcohol consumption increase neuronal activity across neurocircuits in which specific components depend on the vulnerability of individual mice to these stressors. Increased PVH activity observed across both experiments suggests this brain area as a potential mediator of PS-induced increases in alcohol consumption. Future investigations of specific neuronal populations within the PVH activated by PS, and manipulation of these specific neuronal populations, could improve our understanding of the mechanisms leading to PTSD-AUD comorbidity.

Carotid body hypersensitivity in intermittent hypoxia and obtructive sleep apnoea

Carotid bodies are the principal sensory organs for detecting changes in arterial blood oxygen concentration, and the carotid body chemoreflex is a major regulator of the sympathetic tone, blood pressure and breathing. Intermittent hypoxia is a hallmark manifestation of obstructive sleep apnoea (OSA), which is a widespread respiratory disorder. In the first part of this review, we discuss the role of carotid bodies in heightened sympathetic tone and hypertension in rodents treated with intermittent hypoxia, and the underlying cellular, molecular and epigenetic mechanisms. We also present evidence for hitherto-uncharacterized role of carotid body afferents in triggering cellular and molecular changes induced by intermittent hypoxia. In the second part of the review, we present evidence for a contribution of a hypersensitive carotid body to OSA and potential therapeutic intervention to mitigate OSA in a murine model.

The Role of Cortisol in Chronic Stress, Neurodegenerative Diseases, and Psychological Disorders

Cortisol, a critical glucocorticoid hormone produced by the adrenal glands, plays a pivotal role in various physiological processes. Its release is finely orchestrated by the suprachiasmatic nucleus, governing the circadian rhythm and activating the intricate hypothalamic-pituitary-adrenal (HPA) axis, a vital neuroendocrine system responsible for stress response and maintaining homeostasis. Disruptions in cortisol regulation due to chronic stress, disease, and aging have profound implications for multiple bodily systems. Animal models have been instrumental in elucidating these complex cortisol dynamics during stress, shedding light on the interplay between physiological, neuroendocrine, and immune factors in the stress response. These models have also revealed the impact of various stressors, including social hierarchies, highlighting the role of social factors in cortisol regulation. Moreover, chronic stress is closely linked to the progression of neurodegenerative diseases, like Alzheimer's and Parkinson's, driven by excessive cortisol production and HPA axis dysregulation, along with neuroinflammation in the central nervous system. The relationship between cortisol dysregulation and major depressive disorder is complex, characterized by HPA axis hyperactivity and chronic inflammation. Lastly, chronic pain is associated with abnormal cortisol patterns that heighten pain sensitivity and susceptibility. Understanding these multifaceted mechanisms and their effects is essential, as they offer insights into potential interventions to mitigate the detrimental consequences of chronic stress and cortisol dysregulation in these conditions.

Socioeconomic resources in youth are linked to divergent patterns of network integration and segregation across the brain's transmodal axis

Socioeconomic resources (SER) calibrate the developing brain to the current context, which can confer or attenuate risk for psychopathology across the lifespan. Recent multivariate work indicates that SER levels powerfully influence intrinsic functional connectivity patterns across the entire brain. Nevertheless, the neurobiological meaning of these widespread alterations remains poorly understood, despite its translational promise for early risk identification, targeted intervention, and policy reform. In the present study, we leverage the resources of graph theory to precisely characterize multivariate and univariate associations between household SER and the functional integration and segregation (i.e., participation coefficient, within-module degree) of brain regions across major cognitive, affective, and sensorimotor systems during the resting state in 5,821 youth (ages 9-10 years) from the Adolescent Brain Cognitive Development (ABCD) Study. First, we establish that decomposing the brain into profiles of integration and segregation captures more than half of the multivariate association between SER and functional connectivity with greater parsimony (100-fold reduction in number of features) and interpretability. Second, we show that the topological effects of SER are not uniform across the brain; rather, higher SER levels are related to greater integration of somatomotor and subcortical systems, but greater segregation of default mode, orbitofrontal, and cerebellar systems. Finally, we demonstrate that the effects of SER are spatially patterned along the unimodal-transmodal gradient of brain organization. These findings provide critical interpretive context for the established and widespread effects of SER on brain organization, indicating that SER levels differentially configure the intrinsic functional architecture of developing unimodal and transmodal systems. This study highlights both sensorimotor and higher-order networks that may serve as neural markers of environmental stress and opportunity, and which may guide efforts to scaffold healthy neurobehavioral development among disadvantaged communities of youth.

Gestational protein restriction alters early amygdala neurochemistry in male offspring

BACKGROUND

Gestational protein intake restriction-induced long-lasting harmful outcomes in the offspring's organs and systems. However, few studies have focused on this event's impact on the brain's structures and neurochemical compounds.

AIM

The present study investigated the effects on the amygdala neurochemical composition and neuronal structure in gestational protein-restricted male rats' offspring.

METHODS

Dams were maintained on isocaloric standard rodent laboratory chow with regular protein [NP, 17%] or low protein content [LP, 6%]. Total cells were quantified using the Isotropic fractionator method, Neuronal 3D reconstruction, and dendritic tree analysis using the Golgi-Cox technique. Western blot and high-performance liquid chromatography performed neurochemical studies.

RESULTS

The gestational low-protein feeding offspring showed a significant decrease in birth weight up to day 14, associated with unaltered brain weight in youth or adult progenies. The amygdala cell numbers were unchanged, and the dendrites length and dendritic ramifications 3D analysis in LP compared to age-matched NP progeny. However, the current study shows reduced amygdala content of norepinephrine, epinephrine, and dopamine in LP progeny. These offspring observed a significant reduction in the amygdala glucocorticoid (GR) and mineralocorticoid (MR) receptor protein levels. Also corticotrophin-releasing factor (CRF) amygdala protein content was reduced in 7 and 14-day-old LP rats.

CONCLUSION

The observed amygdala neurochemical changes may represent adaptation during embryonic development in response to elevated fetal exposure to maternal corticosteroid levels. In this way, gestational malnutrition stress can alter the amygdala's neurochemical content and may contribute to known behavioral changes induced by gestational protein restriction.

Mechanisms linking neurological disorders with reproductive endocrine dysfunction: Insights from epilepsy research

Gonadal hormone actions in the brain can both worsen and alleviate symptoms of neurological disorders. Although neurological conditions and reproductive endocrine function are seemingly disparate, compelling evidence indicates that reciprocal interactions exist between certain disorders and hypothalamic-pituitary-gonadal (HPG) axis irregularities. Epilepsy is a neurological disorder that shows significant reproductive endocrine dysfunction (RED) in clinical populations. Seizures, particularly those arising from temporal lobe structures, can drive HPG axis alterations, and hormones produced in the HPG axis can reciprocally modulate seizure activity. Despite this relationship, mechanistic links between seizures and RED, and vice versa, are still largely unknown. Here, we review clinical evidence alongside recent investigations in preclinical animal models into the contributions of seizures to HPG axis malfunction, describe the effects of HPG axis hormonal feedback on seizure activity, and discuss how epilepsy research can offer insight into mechanisms linking neurological disorders to HPG axis dysfunction, an understudied area of neuroendocrinology.

The Interaction between Psychological Stress and Iron Status on Early-Life Neurodevelopmental Outcomes

This review presents evidence from animal and human studies demonstrating the possible connection and significant impact of poor iron status and psychological distress on neurocognitive development during pregnancy and the neonatal period, with implications for long-term cognition. Stress and iron deficiency are independently prevalent and thus are frequently comorbid. While iron deficiency and early-life stress independently contribute to long-term neurodevelopmental alterations, their combined effects remain underexplored. Psychological stress responses may engage similar pathways as infectious stress, which alters fundamental iron metabolism processes and cause functional tissue-level iron deficiency. Psychological stress, analogous to but to a lesser degree than infectious stress, activates the hypothalamic-pituitary-adrenocortical (HPA) axis and increases proinflammatory cytokines. Chronic or severe stress is associated with dysregulated HPA axis functioning and a proinflammatory state. This dysregulation may disrupt iron absorption and utilization, likely mediated by the IL-6 activation of hepcidin, a molecule that impedes iron absorption and redistributes total body iron. This narrative review highlights suggestive studies investigating the relationship between psychological stress and iron status and outlines hypothesized mechanistic pathways connecting psychological stress exposure and iron metabolism. We examine findings regarding the overlapping impacts of early stress exposure to iron deficiency and children's neurocognitive development. We propose that studying the influence of psychological stress on iron metabolism is crucial for comprehending neurocognitive development in children exposed to prenatal and early postnatal stressors and for children at risk of early iron insufficiency. We recommend future directions for dual-exposure studies exploring iron as a potential mediating pathway between early stress and offspring neurodevelopment, offering opportunities for targeted interventions.

Adrenocorticotropic hormone secretion in response to anticipatory stress and venepuncture: The role of menstrual phase and oral contraceptive use

INTRODUCTION

Oral contraceptives (OCs) are primarily known for their effects on the reproductive system, but they can also impact the hypothalamic-pituitary-adrenal (HPA) axis. The present study aimed to compare plasma adrenocorticotropic hormone (ACTH) responses to the anticipatory stress of participating in a scientific experiment and venepuncture in OC users versus naturally cycling (NC) women, with a focus on variations throughout the menstrual cycle.

METHODS

We recruited 131 young women (average age 20.5) and obtained blood samples to measure plasma ACTH concentrations immediately after venepuncture and again after 15 min of group activities designed to facilitate interpersonal attachment and stress-buffering.

RESULTS

ACTH levels decreased in 70% of all participants throughout the group activities. A two-way repeated measures ANOVA highlighted a significant interaction between time and OC use, indicating differential changes in ACTH levels during social interaction between OC users and NC women. Further, the post-hoc analysis revealed that a period of stress-buffering group activities significantly decreased ACTH levels in NC women during menstrual and secretory phases, but not during the proliferative phase. In contrast, OC users did not display a decrease during group activities, regardless of the phase.

CONCLUSION

This study underscores the influence of OC use on stress regulation, demonstrating that OCs not only modulate reproductive functions but also impact ACTH stress reactivity. Additionally, it emphasizes the importance of considering hormonal contraceptive use and menstrual cycle phases when assessing female stress responses.

The role of Neurochemicals, Stress Hormones and Immune System in the Positive Feedback Loops between Diabetes, Obesity and Depression

Type 2 diabetes mellitus (T2DM) and depression are significant public health and socioeconomic issues. They commonly co-occur, with T2DM occurring in 11.3% of the US population, while depression has a prevalence of about 9%, with higher rates among youths. Approximately 31% of patients with T2DM suffer from depressive symptoms, with 11.4% having major depressive disorders, which is twice as high as the prevalence of depression in patients without T2DM. Additionally, over 80% of people with T2DM are overweight or obese. This review describes how T2DM and depression can enhance one another, using the same molecular pathways, by synergistically altering the brain's structure and function and reducing the reward obtained from eating. In this article, we reviewed the evidence that eating, especially high-caloric foods, stimulates the limbic system, initiating Reward Deficiency Syndrome. Analogous to other addictive behaviors, neurochemical changes in those with depression and/or T2DM are thought to cause individuals to increase their food intake to obtain the same reward leading to binge eating, weight gain and obesity. Treating the symptoms of T2DM, such as lowering HbA1c, without addressing the underlying pathways has little chance of eliminating the disease. Targeting the immune system, stress circuit, melatonin, and other alterations may be more effective.

Exploration of possible sex bias in acute social stress research: a semi-systematic review

Stress can have a significant impact on the daily lives of individuals and can increase vulnerability to a number of medical conditions. This study aims to estimate the ratio of male to female participants in acute social stress research in healthy individuals. We examined original research articles published over the last 20 years. Each article was screened to determine the total number of female and male participants. We extracted data from 124 articles involving a total of 9539 participants. A total of 4221 (44.2%) participants were female, 5056 (53.0%) were male and 262 (2.7%) were unreported. Articles incorporating only females were significantly underrepresented compared to articles incorporating only males. Forty articles (63.5%) which presented data from both females and males, failed to analyse and interpret the results by sex, a significant methodological limitation. In conclusion, in the literature published over the last 20 years, female participants are significantly underrepresented. In the studies where females are represented, severe methodological limitations are apparent. Researchers should be conscious of sexual dimorphism, menstrual phase and use of hormonal contraception, which may impact the interpretation of their results.