Neurobiology of Stress

Stressful experiences are a major risk factor for the development of neuropsychiatric disorders in vulnerable individuals. Identifying features that can distinguish stress-susceptible from resilient individuals remains a central goal in stress neurobiology. Due to the routine exclusion of female subjects from stress research or the use of male-defined criteria in behavioral characterization of subjects post-stress, female stress responses and vulnerability profiles remain poorly understood. This work aimed to gain a better understanding of sex-specific stress responses to social defeat stress. Here, we used a novel paired male-female social defeat paradigm and tracked subjects longitudinally in a ''two-hit'' design to evaluate responses to both acute social defeat stress (ASDS) and chronic social defeat stress (CSDS), and to determine how prior stress exposure influences subsequent vulnerability. We found that both ASDS and CSDS induces changes in social avoidance/approach behavior in males but not females, as measured by a classic social interaction ratio. Prior ASDS exposure enhanced susceptibility to subsequent CSDS most clearly in males, with females displaying specific changes in corner zone occupancy. Furthermore, we observed divergent anxiety profiles between males and females in a post-stress behavioral battery. Finally, females exhibited specific stress-related locomotor responses following ASDS. Together, these findings suggest that females may adopt distinct behavioral strategies following social defeat stress.

Chronic stress is a major risk factor for psychiatric disorders such as depression and anxiety, yet the biological basis of individual differences in stress susceptibility and resilience remains poorly understood. Here, we examined physiological, behavioral, and medial prefrontal cortex (mPFC) transcriptomic responses to chronic restraint stress (CRS) in male BALB/c and C57BL/6J mice. After 21 days of CRS, BALB/c mice exhibited greater stress-related changes than C57BL/6J mice, including greater body weight loss, elevated serum corticosterone, reduced serum antioxidant capacity, and more pronounced depression-like behaviors. RNA sequencing showed largely strain-specific transcriptional changes in the mPFC. Strain x stress interaction analysis, followed by canonical pathway analysis using Ingenuity Pathway Analysis (IPA), identified strain-dependent molecular signatures. The most prominent differences involved extracellular matrix (ECM) organization and remodeling and neuroinflammatory signaling pathways, with greater predicted activation in BALB/c mice. IPA upstream regulator analysis further predicted multiple candidate regulators associated with these pathways, including TGF-{beta}/SMAD, C4a/C4b, and MAPK14. Among genes associated with these pathways, several ECM-related genes were preferentially upregulated in BALB/c mice, whereas activity-dependent immediate early genes were preferentially downregulated in C57BL/6J mice. These findings suggest that the strain-dependent mPFC transcriptional programs identified here may contribute to differential stress susceptibility and resilience.

Extensive work has established that exposure to a single acute stressor can have profound impacts on future reactivity to new stressors, including enhanced acquisition of new fear. The impact of stressor type on development of stress sensitization, however, remains unclear. We investigated whether fundamentally different acute stressors (shock, social defeat, or restraint stress) differ in ability to sensitize acquisition of a new, contextually distinct fear memory in adult male mice two weeks following stress exposure. Stressor subtype differentially sensitized new fear learning; specifically, shock and social defeat - but not restraint stress - led to enhanced recall of a new shock-paired fear memory. We also compared how stressor subtypes differentially engage the brain-periphery interactions that regulate stress responsivity. Notably, restraint stress, which did not lead to fear sensitization to foot shock, drove similar or even greater corticosterone release than other stressors, suggesting that the neuroendocrine response to the original stressor is dissociable from development of a behavioural fear sensitization response. Using the immediate-early gene FOS as a marker of neural activity, all conditions - including the context-only control condition - activated a similar number of neurons in the basolateral amygdala. In contrast, only stressful conditions activated the paraventricular nucleus of the hypothalamus, and restraint stress selectively spared activation of the dorsal hippocampus. These data collectively suggest that future responses to stress depend critically on the identity of previously experienced stressors, rather than simply on prior exposure to stress, establishing a powerful comparative model for investigating the specific mechanisms underlying stress-enhanced fear learning.

Early-life adversity during critical developmental windows markedly increases vulnerability to neuropsychiatric disorders later in life. Although adult behavioral and neurobiological alterations following early stress are well documented, the early emerging phenotypes and their underlying cellular and molecular mechanisms during juvenile development remain poorly understood. In this study, we utilized the translational Scarcity-Adversity Model (SAM) to investigate early behavioral alterations and hippocampal neuroplasticity in juvenile offspring. We characterized the behavioral profile of juvenile subjects exposed to SAM to identify early manifestations of vulnerability. Next, we evaluated hippocampal neurogenesis by quantifying neural progenitor cell proliferation immediately following stress exposure (at postnatal day 13, PND 13) and the short-term survival of newborn neurons (1 week post-labeling) in the dentate gyrus of juvenile offspring. Furthermore, given the functional compartmentalization of the hippocampus, we measured the protein expression of mature BDNF (mBDNF) and its precursor proBDNF across both dorsal and ventral domains. At the behavioral level, SAM-exposed juvenile offspring exhibited increased immobility in the forced swim test alongside impaired spatial memory in the novel object location task. Regarding hippocampal neurogenesis, SAM exposure did not alter immediate progenitor proliferation at PND 13; however, it produced a significant, male-specific reduction in newborn neuron survival, concomitant with a trend toward decreased mBDNF levels in males. Together, these results provide critical insight into the early neurodevelopmental trajectories triggered by early-life adversity, identifying early behavioral impairments and male-specific neuroplastic deficits as key juvenile markers of vulnerability preceding adult psychopathology.

This study followed the recruitment of medial prefrontal cortex parvalbumin (PV+) interneurons and their perineuronal nets (PNN) across the two stages of the learned helplessness (LH) paradigm: the initial uncontrollable stress experience and the later expression of helpless or resilient coping. Combining TRAP2-based activity mapping with a staggered-endpoint design, three main findings emerged on the functional and structural neuronal correlates in prelimbic (PL) and infralimbic (ILA) subregions during LH paradigm. First, prefrontal recruitment during the first inescapable shock session already predicted the coping strategy that would be expressed two days later during escape avoidance test, before any behavioral divergence was observable. Second, the expression of parvalbumin protein (PV) in this cortical subpopulation of interneurons followed a dynamic trajectory rather than a static stress change, transiently reduced across all shocked animals at the escape test, and back to baseline over the following week in both PL and ILA, except in animals that went on to be classified as helpless. Third, PNN intensity temporal patterns did not track stress exposure in either subregion, yet PNN and PV became correlated with one another specifically in ILA in stressed animals, pointing to a stress-induced structural coupling rather than a constitutive relationship between the two markers.

The integration of separate memories sharing overlapping elements allows for inferring relationships between events that have never been experienced together. Recent findings indicate that stress impairs this process of mnemonic inference, which may have important implications for stress-related psychopathologies. However, the mechanisms underlying such impairments remain largely unknown. To elucidate the neuroendocrine mechanisms by which stress affects mnemonic inference, mice were first trained on two sets of auditory visual cue associations. Afterwards, one of the visual cues was paired with reward. Mnemonic inference was probed by examining reward seeking behavior in response to the auditory cues alone. Control mice successfully inferred the auditory cue outcome association, selectively seeking reward in response to the auditory cue associated with the rewarded visual cue. In contrast, systemic administration of the stress hormone corticosterone before testing impaired inference accuracy, leading mice to seek reward to both auditory cues. Corticosterone administration was accompanied by increased noradrenergic activity, and stimulation of noradrenergic signaling with yohimbine similarly disrupted inference accuracy. Conversely, the beta adrenoceptor antagonist propranolol prevented the corticosterone induced impairment, indicating that corticosterone effects depend on concurrent noradrenergic activation. At the neural level, the corticosterone induced mnemonic inference impairment was associated with enhanced GABAergic inhibition of pyramidal neurons in the hippocampal CA3 region. Furthermore, hippocampal administration of the GABAA receptor antagonist bicuculline prevented the corticosterone induced impairment in mnemonic inference. Together, these findings identify a glucocorticoid noradrenergic mechanism that disrupts mnemonic inference through enhanced GABAergic inhibition in hippocampal CA3, providing an account of how stress hormones impair inferential memory.

It is estimated that approximately fifty percent of the population will encounter at least one traumatic event during their lifetime; however, only six percent develop Posttraumatic Stress Disorder (PTSD), a trauma-related disorder characterized by persistent alterations in affect and cognition, including an exaggerated fear response. It is well established that females (9.7%) are more than twice as likely as males (3.6%) to be diagnosed with PTSD. Nevertheless, a significant challenge remains in understanding how the severity of traumas experienced in childhood versus adulthood influences PTSD development across sexes. To address this challenge effectively, the adoption of preclinical animal models that accurately reflect these key characteristics is crucial. The Stress Enhanced Fear Learning (SEFL) paradigm in rodents encapsulates some of these complexities associated with PTSD, such as persistent fear sensitization following exposure to acute trauma. This study investigates how stress severity and developmental timing affect the long-term maintenance of SEFL in male and female rats. Juvenile and adult rats were initially subjected to no stress (control, context only), low stress (1 footshock), moderate stress (3 footshocks), or high stress (15 footshocks), followed by an extinction session either one day (recent) or sixty days (remote) later. Subsequently, to evaluate SEFL in a new context, all subjects received a single footshock and were tested the following day. Shortly after stress induction, all groups displayed SEFL. Although the effects persisted for sixty days in adult males and juvenile females, even at the lowest stress level, they were significantly reduced in juvenile males and adult females. These findings offer novel insights into sex-related differences in the persistence of SEFL and introduce new considerations regarding how the timing of developmental stressors influences future threat encoding and fear responses.

Background Childhood adversity is linked to psychopathology risk and dysregulated stress reactivity; however, unified underlying neural mechanisms are unclear. A central visceral network, including the bed nucleus of the stria terminalis (BNST), amygdala and subgenual anterior cingulate cortex (sgACC), is implicated in affective processes and proximally controls stress reactivity. We examined relationships among childhood adversity, stressor-evoked neural activity/connectivity and affective and cardiovascular outcomes. Methods Participants were adults (n=97, mean age=27.32, SD=4.02, 57 females) uniformly distributed across physical abuse severity. Childhood adversity was assessed by threat (abuse or traumatic events) and socioeconomic deprivation (SED). Participants performed an fMRI stress task with cardiovascular recordings. Linear/curvilinear regressions were performed with threat and deprivation together as predictors of stressor-evoked activity/connectivity. Neural variables showing significant adversity associations were examined as predictors of affective symptoms/diagnoses or cardiovascular responses. Results Threat and SED displayed opposing curvilinear relationships with stressor-evoked amygdala and sgACC activity, respectively: at low and high adversity, amygdala reactivity was greater, whereas sgACC reactivity was blunted. Greater SED was associated with weaker BNST-sgACC connectivity. Blunted amygdala reactivity and lower sgACC reactivity were associated with greater post-traumatic stress symptoms. Affective diagnoses peaked at near-zero BNST-sgACC connectivity. Greater amygdala reactivity was associated with blunted diastolic blood pressure reactivity and recovery. Conclusions The curvilinear relationships suggest adversity-related vulnerability thresholds. Blunted amygdala, lower sgACC reactivity and weaker BNST-sgACC connectivity may confer affective risk, whereas heightened amygdala reactivity may confer cardiovascular risk. Our findings support a central visceral network pathway by which childhood adversity may contribute to affective and cardiovascular health.

Early-life stress is associated with alterations in amygdala volume, but findings vary across studies and species. Rodent models typically report increased amygdala volume, whereas human studies often find reductions or mixed effects. We propose the amygdala burnout hypothesis, which suggests that early-life stress alters amygdala developmental trajectories, producing initial volumetric increases that are followed by reductions later in life. To test this hypothesis, we examined amygdala development across rodent and human cohorts spanning adolescence to older adulthood. In rodents, chronic stress was associated with increased amygdala nuclei volumes during adolescence. Comparable increases were observed in adolescents from the IMAGEN consortium, with evidence of a dose-dependent association between childhood stress and amygdala developmental trajectories. In contrast, analyses of older adults from the UK Biobank revealed reduced bilateral amygdala volume associated with early-life stress. Together, these findings support a developmental model that reconciles previously conflicting observations across species and age groups. Early-life stress is associated with alterations in amygdala volume, but findings vary across studies and species. Rodent models typically report increased amygdala volume, whereas human studies often find reductions or mixed effects. We propose the amygdala burnout hypothesis, which suggests that early-life stress alters amygdala developmental trajectories, producing initial volumetric increases that are followed by reductions later in life. To test this hypothesis, we examined amygdala development across rodent and human cohorts spanning adolescence to older adulthood. In rodents, chronic stress was associated with increased amygdala nuclei volumes during adolescence. Comparable increases were observed in adolescents from the IMAGEN consortium, with evidence of a dose-dependent association between childhood stress and amygdala developmental trajectories. In contrast, analyses of older adults from the UK Biobank revealed reduced bilateral amygdala volume associated with early-life stress. Together, these findings support a developmental model that reconciles previously conflicting observations across species and age groups.

Early-life psychosocial adversity increases vulnerability to stress-related disorders and may begin as early as prior to conception via maternal stress. Consequently, early-life stress (ELS) in offspring may accumulate across early development. The short-allele variant of the serotonin transporter (SERT) gene has been implicated in depression risk and higher anxiety sensitivity following stress exposure, but for cumulative ELS it is unknown whether behavioral effects depend on the SERT genotype. In this study, we used heterozygous SERT knockout (SERT+/-) rats to model reduced SERT expression similar to human short-allele carriers. To investigate the effects of cumulative ELS on offspring behavioral phenotype, dams were exposed to stress before, during and after pregnancy, combined with offspring postnatal maternal separation. Cognitive, affective, and social behaviors were assessed in wild-type (WT) and SERT+/- (HET) male and female adults. Maternal care and anhedonia-like behaviors in dams were also assessed. Dams exposed to the cumulative stress (STR) displayed increased arched-back licking and grooming compared to controls (CTR). In the offspring, HET rats showed increased social investigation and tended to display hyperactivity compared to WT. Anxiety-like behavior was higher in HET females compared to WT females, with no genotype differences in males. Independent of genotype, STR rats consumed less sucrose and showed impaired object recognition compared to CTR; however, HET-STR rats performed better in the object recognition than WT-STR rats. A significant SERT genotype x cumulative ELS x sex interaction revealed opposing, sex-dependent effects on anxiety-like behavior. HET-STR females showed more anxiety-like responses relative to HET-CTR and WT-STR females, as well as HET-STR males. In contrast, HET-STR males were less anxious than HET-CTR and WT-STR males. Reduced SERT expression is linked to more social investigation alongside increased anxiety, particularly in SERT+/- females. While cumulative ELS did not induce robust anxiety-like and depressive-like phenotypes, overall, it impaired memory performance, an effect partially mitigated in SERT+/- rats. Notably, the SERT genotype differentially modulated anxiety-like behavior in male versus female offspring, increasing vulnerability in SERT+/- females while reducing it in SERT+/- males, an effect further amplified by exposure to cumulative ELS. These results underscore sex as a critical determinant in the interaction between genetic susceptibility and cumulative exposure to early adversity in shaping affective outcomes.

Exposure to chronic environmental challenges triggers divergent behavioral trajectories across individuals. At the core, these different trajectories can be classified as individuals actively adapting to the challenges ("responders") and those displaying a rigid, non-responsive phenotype ("non-responders"). The brain system-wide network configurations that dictate why individuals diverge along these differential coping strategies, which can also lead to disease vulnerability or resilience, remain poorly understood. Here, we paired machine-learning-based deep behavioral phenotyping with multi-modal whole-brain imaging, integrating longitudinal Manganese-Enhanced MRI (MEMRI) and post-challenge cFOS mapping, to chart the functional landscape of individual stress trajectories in mice subjected to chronic social defeat stress. High-dimensional behavioral phenotyping revealed that active stress adaptation is a complex trajectory marked by latent, pre-stress kinetic signatures in vigilance-like and locomotive behaviors. At the neural level, longitudinal MEMRI captured distinct, consolidated activity reconfigurations across canonical valence and stress-regulatory circuits that segregated responders from non-responders. Complementary whole-brain cellular cFOS network analysis after an additional acute challenge revealed that non-responders exhibited marked hyper-modularity and network fragmentation, whereas responders feature a tightly integrated functional module co-clustering the periaqueductal gray, ventral tegmental area, basolateral amygdala (BLA), and dorsal raphe (DR). Notably, functional network connectivity along the DR-BLA axis was completely lost in non-responsive animals. Finally, pathway-specific chemogenetic inhibition of BLA-projecting DR neurons during a social challenge significantly attenuated social avoidance and reversed anxiety-like behavioral deficits, effectively shifting active behavioral adaptation toward a non-responsive phenotype. Together, these findings demonstrate that individual stress-coping strategies are driven by coordinated, system-wide reconfigurations of activity and plasticity, identifying the DR-BLA circuit as a critical gatekeeper of adaptive stress responses. Graphical AbstractGlobal neural functional alterations defining responding vs non-responding populations following chronic stress are understudied, yet crucial. Deep phenotyping followed by mapping brain-wide activity and plasticity changes identified these underlying divergent functional networks. Acute manipulation of a dorsal raphe - basolateral amygdala pathway ameliorated adaptive stress responses, highlighting the significance of this network-based approach. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/740522v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1850a04org.highwire.dtl.DTLVardef@1549284org.highwire.dtl.DTLVardef@15f3ebforg.highwire.dtl.DTLVardef@107ca9_HPS_FORMAT_FIGEXP M_FIG C_FIG

Acute disturbances of the light-dark cycle may lead to cognitive impairments associated with disturbances in hippocampal functions in humans and rodent models that are potentially governed by subcortical modulation. In this study, we applied a jet-lag-like model in mice by introducing a six-hour delay of the switch towards the light, inactive phase of mice following a contextual fear conditioning training. Phase delay (PD) resulted in a reduced fear memory expression in male but not female, associated with a sex-specific activation of orexinergic neurons in the lateral hypothalamus (LH) as well as of cells in the supramammillary nucleus (SuM) and in the hilus of the dorsal hippocampal dentate gyrus (DG), as assessed by immunolabelling for the activity marker c-Fos. Mimicking the overactivation of SuM and DG by chemogenetic stimulation before contextual fear memory retrieval replicated the PD-induced phenotype, suggesting a direct contribution of the SuM and the DG on modulating fear expression after PD. Further circuit analysis by c-Fos revealed a reciprocal interaction between the SuM and the DG. In addition, orexinergic neurons in the LH were activated by chemogenetic stimulation of the SuM. Together, our results reveal that an acute, jet-lag-like phase shift applied during late consolidation stages induced deficits in fear memory expression associated with an overactivation of the SuM-DG pathway and the orexinergic system. These findings may provide insights into the subcortical modulation of memory-relevant circuits, with relevance for acute light-dark rhythm disruptions prevalent in modern societies as well as for disorders associated with memory disturbances. Significance statementAcute disturbances of the light-dark cycle, as experienced during jet lag or shift work, are increasingly common and can impair memory and cognitive function. Here, we identify a brain circuit underlying jet-lag-induced fear memory deficits that occurs selectively in male, but not female mice. A six-hour delay of the dark phase impaired recall of a previously learned fear memory in males, associated with overactivation of two interconnected brain regions, the supramammillary nucleus and the dentate gyrus of the hippocampus, as well as neurons producing the wake-promoting signal orexin. Artificially mimicking this overactivation was sufficient to reproduce the memory impairment, revealing a hypothalamo-hippocampal circuit that translates circadian disruption into memory deficits, with implications for cognitive disorders and sex-specific vulnerability.

Fear memories in post-traumatic stress disorder are marked by persistent cue-driven recollection and impaired contextual recall, yet the engram organization underlying this maladaptive state remains unclear. Here we used a rodent model combining contextual fear conditioning with systemic corticosterone to mimic trauma-associated glucocorticoid exposure. This paradigm generated a PTSD-like phenotype characterized by hypermnesia for a trauma-related but irrelevant (non-predictive of the threat) cue and contextual amnesia. Activity-dependent tagging and reactivation mapping revealed that traumatic memory is supported by a regionally dysregulated engram pattern, with enhanced recruitment of the anterior cingulate cortex (ACC) and basolateral amygdala (BLA), and reduced engagement of the dentate gyrus (DG). These changes persisted over time and correlated with the severity of the behavioral phenotype. Chemogenetic inhibition of ACC engram cells abolished traumatic memory expression, restored contextual recall, and normalized engram reactivation across DG and BLA. In contrast, inhibition of randomly tagged ACC or hippocampal populations had no such effect, indicating that the ACC engram is specifically required for traumatic memory expression. Together, these findings show that PTSD-like memory is not simply an amplified fear trace, but a distinct maladaptive engram state distributed across cortical-hippocampal- amygdalar circuits.

Disruptions to maternal behaviors that emerge during the peripartum period have been shown to have lasting physiological and behavioral consequences for offspring. In addition to effects on offspring, disrupted maternal behaviors have been associated with peripartum mood and anxiety disorders. Therefore, it is critical for the wellbeing of both mother and offspring to identify upstream risk factors for the disruption of maternal behavior. We have previously found that pubertal stress leads to a blunted hypothalamic-pituitary-adrenal (HPA) axis response in peripartum humans and mice. Given that dysfunction of the HPA axis is associated with both PMADs and disrupted maternal behavior, we examined how pubertal stress influenced maternal behavior throughout peripartum in mice using a pup retrieval test. We found that pubertal stress led to faster pup retrieval, but a less predictable pattern of maternal behavior, as well as a blunted HPA axis response during pregnancy. We also examined whether maternal pubertal stress influenced offspring behavior in adolescence and adulthood. We found sex-specific differences in risk-taking behavior during adolescence that are no longer present in adulthood. Finally, we used in situ hybridization to examine gene expression during pregnancy in the medial preoptic area of the hypothalamus, a region implicated in maternal behavior. Following pubertal stress, we found cell-type specific changes in the expression of genes necessary for the expression of maternal behavior. Collectively, these findings contribute to our understanding of upstream risk factors for peripartum disruptions to maternal behavior and the lasting effects of pubertal stress on both mother and offspring.

The prevalence of neurodevelopmental disorders (NDDs) has increased dramatically, with growing evidence linking prenatal maternal stress exposure to NDDs. Across diverse maternal stressors, immune dysregulation emerges as a common feature, suggesting that fetal microglia may detect changes in the intrauterine environment and influence neurodevelopment. Accordingly, we utilized a mouse model of prenatal maternal cold stress to investigate the impact of maternal stress during pregnancy on fetal microglia morphology, cellular interactions, and phagocytic behaviors. Pregnant mice were exposed to cold stress from embryonic day 11.5 (E11.5) to E15.5 and fetal hypothalamic tissue was assessed from both male and female embryos. By adapting the morphology analysis toolset MicrogliaMorphology to assess fetal microglia, we demonstrate regional differences in microglial morphology in the fetal hypothalamus at baseline, with hypothalamic nuclei such as the paraventricular nucleus (PVN) containing fewer rod-like microglia compared to the broader hypothalamus. Interestingly, prenatal maternal cold stress induced a male-specific shift in microglial morphology from ameboid to ramified within the E15.5 PVN. Male embryos also displayed increased microglial-arginine vasopressin (AVP) neuronal interactions and microglial phagocytosis within the E15.5 PVN, but these changes were unique to microglia with a ramified morphology and were not observed when microglia with an ameboid or rod-like morphology were assessed. Using pHrodo bioparticles and flow cytometry, we further illustrate that prenatal maternal cold stress drives increased phagocytic activity in the E15.5 hypothalamus of male embryos, but not females. Together, these data demonstrate that prenatal maternal cold stress alters microglia morphology and drives morphology-dependent microglial interactions and phagocytic behaviors in male embryos which are unique to the hypothalamic PVN--a nuclei critical for social behaviors. Our findings also suggest that specific hypothalamic nuclei such as the PVN may be more sensitive to prenatal maternal stress, which has the potential to provide a cellular basis underlying the sex differences in microglia-dependent social deficits that were previously reported for this model.

Early life adversity (ELA) is a leading preventable contributor to morbidity and mortality, increasing risk for mental and physical illness later in life. However, mechanisms linking ELA to comorbid outcomes within both the brain and body remain poorly understood. We tested whether ELA disrupts functional and molecular development of vagal circuitry, a key pathway for brain-body communication, using the limited bedding and nesting (LBN) mouse model of unpredictable maternal care. We measured vagally mediated autonomic stress responses longitudinally using three noninvasive measures of heart rate variability (HRV). This is the first time the development of the vagally-mediated autonomic stress response has been measured in mice. We also performed single-nucleus RNA sequencing of the vagal medulla immediately after LBN and in adulthood, followed by spatial mapping of high-confidence differentially expressed genes. ELA altered trajectories of all HRV measures, with pronounced sex differences. ELA females showed precocious maturation followed by adult declines, whereas males initially exhibited blunted responses but recovered to control levels. Transcriptomic changes were also sex dependent, with female neurons exhibiting signatures of mitochondrial dysfunction, while males showed adaptive mitochondrial responses. Spatial mapping revealed rostro-caudal organization, localizing adaptive male responses to the rostral and intermediate vagal medulla and maladaptive female responses to the intermediate vagal medulla and loose nucleus ambiguus. These findings demonstrate enduring, sex-specific alterations in vagal circuit development centered on mitochondrial pathways.

Stress-related experiences alter glutamatergic signaling and neuronal excitability, but the mechanisms that couple experience to dentate granule cell function remain incompletely understood. Here, we examined how protein kinase N1a (PKN1a), a protein kinase C-like serine/threonine kinase, and repeated swim exposure regulate mouse hippocampal dentate granule cell excitability, with a focus on the neuronal glutamate transporter excitatory amino acid transporter 3 (EAAT3) and group I metabotropic glutamate receptors (mGluRs). Five days of repeated swim exposure increased spike firing in mature dentate granule cells from wild-type mice. PKN1a knockout produced a similar increase, and repeated swim did not further enhance firing in knockout mice. The enhanced firing observed after repeated swim exposure and in PKN1a knockout mice was reduced by co-application of an mGluR1 antagonist (LY367385) and an mGluR5 antagonist (MPEP). Inhibition of glutamate transporters with DL-TBOA increased granule cell firing in control wild-type mice but did not further increase firing in repeated-swim wild-type or PKN1a knockout mice, suggesting occlusion of transporter-dependent regulation of excitability. Repeated swim exposure and PKN1a knockout also reduced total and surface expression of EAAT3 in the hippocampus, whereas expression of the glial glutamate transporter EAAT2 was not significantly altered. Finally, PKN1a knockout and repeated swim exposure reduced anxiety-related behavior in the elevated plus maze test. Thus, PKN1a-dependent regulation of EAAT3 may restrain group I mGluR-dependent excitability in dentate granule cells, whereas repeated swim exposure and PKN1a knockout shift this system toward a lower-EAAT3, higher-excitability state accompanied by reduced anxiety-related behavior.

Background: Psychological health is an important aspect of health and well-being among adults with irritable bowel syndrome, yet the interrelationships among individual vulnerabilities, social experiences, perceived stress, and psychological health outcomes remain poorly understood. Objective: To characterize psychological health and examine direct and indirect associations of childhood adversity and adult attention-deficit/hyperactivity disorder-related symptoms within an adapted Stress Process Model. Design: Cross-sectional secondary analysis. Setting: The United States All of Us Research Program. Participants: 2,417 adults with electronic health record-documented irritable bowel syndrome and complete data on the primary analysis variables and covariates. Methods: Separate structural equation models examined childhood adversity and adult attention-deficit/hyperactivity disorder-related symptoms in relation to perceived stress, anxiety and depressive symptoms, and positive psychological well-being, with loneliness and perceived social support as psychosocial pathways. Models adjusted for sociodemographic and social-context factors. Results: The median age was 54.39 years; 80.7% were female and 84.4% were White. Moderate-to-high perceived stress was reported by 56.2%, at least moderate anxiety symptoms by 21.0%, and at least moderate depressive symptoms by 24.3%. Higher ACE-8 scores were associated with greater perceived stress, anxiety symptoms, and depressive symptoms and lower psychological well-being ({beta} = 0.063, 0.089, 0.116, and -0.100, respectively); corresponding associations for higher ASRS-6 scores were {beta} = 0.299, 0.355, 0.390, and -0.260. Loneliness-specific indirect associations were positive for perceived stress, anxiety, and depressive symptoms (ACE-8: {beta} = 0.023-0.034; ASRS-6: {beta} = 0.043-0.075) and negative for psychological well-being (ACE-8: {beta} = -0.039; ASRS-6: {beta} = -0.089; all p < .001). Social support-specific indirect associations were not significant in the ACE-8 model and were small and significant only for anxiety and depression in the ASRS-6 model ({beta} = 0.003-0.004). Conclusions: Psychological health among adults with irritable bowel syndrome was associated with interconnected individual and social factors within an adapted Stress Process Model. Childhood adversity and adult attention-deficit/hyperactivity disorder-related symptoms showed direct and indirect associations with psychological health, with loneliness emerging as the most consistent social factor. These findings support prospective investigation of individual vulnerabilities and social experiences in psychological health. The cross-sectional design does not establish temporal ordering or causal mediation.

Stressors experienced during the postnatal period may increase vulnerability to mental health disorders, including postpartum depression and anxiety. In rodents, maternal separation (MS) has been shown to alter behaviours in dams, but these observations have been made almost exclusively in rats and thus robust mouse models of postpartum mental health disorders using this stressor remain limited. Here we first examined, in mice, the effects of MS on maternal caregiving and on anxiety- and depressive-like behaviours. As stress-induced inflammatory activation in the gut-brain axis has been associated with behavioural alterations in non-postpartum contexts, changes in pro-inflammatory cytokines and tight junction proteins in the brain and intestinal tract were also examined. Female C57BL/6N mice were assigned to a No Separation (NS) or a MS condition that consisted of 3-hour daily separation sessions from postnatal days (P) 2 to 14. Maternal care behaviours were assessed on P3 and P7, followed by anxiety- and depressive-like behaviours on P22 and P23, and the collection of the medial prefrontal cortex (mPFC) and colon on P24 to determine the expression of selected genes. Caregiving patterns in MS dams fluctuated throughout the early postnatal period. Although behaviours and gene expression outcomes remained unchanged by MS, grooming time in the splash test was correlated with the expression of different genes in the mPFC. These findings suggest that C57BL/6 mouse dams may be less sensitive to the actions of MS on behaviour and on brain and intestinal markers of inflammation and barrier permeability, at least when examined shortly after weaning.

Interleukin-17A (IL-17A) has been implicated in stress- and pain-related inflammation, yet evidence for acute IL-17A stress response in humans remains scarce. This study examined whether the Maastricht Acute Stress Test (MAST) induces changes in circulating IL-17A and how IL-17A dynamics relate to cortisol and subjective stress/pain. Forty-six healthy adults (mean age: 30.50, SD = 12.86 years; 54% female) completed the standardized MAST. Serum IL-17A and cortisol were assessed repeatedly across baseline and recovery. Stress- and pain-related ratings (VAS) and trait questionnaires (e.g., chronic stress, psychological distress, resilience) were completed. There was a significant increase over time in IL-17A and cortisol following the MAST, with an 36 % increase of IL-17A level measured at 105 min post-stressor and cortisol peaking at 10 min post-stressor. IL-17A indices (baseline and AUCi) showed no meaningful associations with cortisol, subjective stress/pain, or psychological traits, whereas cortisol response (AUCi) correlated positively with perceived acute stress and pain. Overall, the MAST produced clear IL-17A and cortisol responses that appeared dissociable in healthy individuals. Future studies should include broader inflammatory panels and clinical or high-stress samples to clarify conditions under which IL-17A covaries with HPA-axis activity and subjective experience.