Hormones and Behavior

In mammals, sex differences in the brain arise from genetic and hormonal factors, including organizational effects of perinatal testosterone. Epigenetic mechanisms including DNA methylation and demethylation have emerged as critical mediators of brain masculinization; specifically, their regulatory enzymes are upregulated in neonatal mice during the critical period of sexual differentiation, with their inhibition abolishing sex-specific cellular phenotypes. Here, we assessed sex differences in gene expression of the DNA demethylation machinery (Tet1, Tet2, Tet3, Gadd45a, Gadd45b and Tdg) during and after the critical period, and examined how these differences relate to the oxytocinergic system. mRNA expression was measured in the prefrontal cortex (PFC), preoptic area (POA) and paraventricular nucleus of the hypothalamus (PVN) at postnatal day (P) 7 and P18. At P7, males showed higher expression of all six genes than females in PFC, with no differences in POA or PVN; by P18, no regional differences remained. Oxytocin (OXT) immunoreactivity was surveyed across periventricular nucleus (Pe), anteroventral periventricular nucleus (AVPe), POA, PVN and supraoptic nucleus (SON). OXT was undetectable in the POA, AVPe and Pe at P7, and no sex differences were found in PVN or SON at either age, or in AVPe at P18. At P18, females showed higher OXT-immunoreactivity in the Pe and POA, than males. For Oxtr, qPCR revealed higher mRNA expression in the PFC of males at P7, with no other regional differences and none remaining at P18. Together, these findings suggest that sex differences in oxytocinergic regions arise from sex-specific epigenetic regulation during the critical period, and that perinatal testosterone may program DNA methylation dynamics underlying sex-specific gene expression in the developing brain. Our results support a model in which testosterone-dependent epigenetic mechanisms contribute to the sexual differentiation of neuroendocrine circuits, linking hormonal signals to long-term brain organization.

Fear conditioning studies have historically relied on freezing as the primary measure of conditioned fear despite evidence that defensive responding is behaviorally diverse and sexually dimorphic. The endogenous opioid system, particularly mu-opioid receptor (MOR) signaling, is known to regulate fear learning and conditioned analgesia, yet its role in alternative fear-related behaviors and sex differences remains unclear. Here, we investigated the effects of systemic naloxone administration prior to auditory fear conditioning on freezing, darting, shock responsivity, and ultrasonic vocalizations (USVs) in male and female rats. Adult Sprague Dawley rats received naloxone (5 mg/kg, i.p.) or saline prior to conditioning and underwent fear recall testing 24 hours later. Naloxone produced sex- and behavior-specific effects across conditioning and recall. During conditioning, naloxone increased freezing in males during baseline and early tone presentations, while females exhibited reduced shock-response velocity and increased post-shock freezing. Naloxone did not significantly alter darting or USV production during conditioning. During recall, freezing behavior did not differ across groups. Naloxone-treated females, however, exhibited a distinct alarm-calling pattern, with fewer callers overall but increased call output among those that vocalized. These findings suggest that MOR antagonism differentially alters distinct components of fear expression in a sex-dependent manner and support the idea that freezing and alarm calling may reflect separable aspects of fear processing.

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.

People often must decide how long to continue waiting for rewards that will arrive at an uncertain time in the future. We propose that these persistence decisions involve weighing the benefits of continued waiting against opportunity costs of waiting, a balance that may shift over time. This framework suggests that persistence decisions share neural mechanisms with foraging decisions, which require ongoing comparisons between a current resource and possible alternatives. Dopamine and serotonin have been proposed to play opposing roles in foraging, with dopamine promoting exploration and serotonin promoting exploitation. Here we investigated their roles in persistence. In a within-subjects, double-blind, placebo-controlled study in young adults (n = 42), we examined the effects of increasing dopamine with L-dopa and increasing serotonin with escitalopram. We predicted that L-dopa would decrease persistence and escitalopram would increase it. Participants also completed patch-foraging, time perception, risk tolerance, and temporal discounting tasks to explore potential mechanisms of drug effects on persistence. Escitalopram increased persistence, after adjusting for the effects of anxiety and condition order, such that participants waited longer for rewards after taking the serotonergic drug. L-dopa did not influence persistence. In exploratory analyses controlling for age, however, L-dopa reduced persistence and increased exploration in foraging.

Animals experience stressors in a variety of contexts that result in activation of neuroendocrine and cellular stress responses. Release of stress hormones can disrupt or restore redox homeostasis, and the resulting changes in oxidative states, physiology and behavior vary by an individuals stress coping style. However, oxidative stress can also directly modulate neuroendocrine stress signaling. To what extent individual differences in brain antioxidant levels alter behavioral stress levels is not well understood. The present study investigated how N-acetylcysteine amide (NACA), an antioxidant and glutamate-modulating compound, regulates stress behavior across zebrafish (Danio rerio) with different stress coping styles (proactive, reactive). Following 24-hour exposure to NACA or control conditions, we quantified individual and composite stress behaviors using a Light-Dark Test (LDT). As expected, both proactive fish and NACA-treated fish showed significantly lower stress behaviors compared to reactive and control animals, respectively. Notably, stress-reducing effects of NACA were only seen in those with a reactive stress coping style. Overall, our data suggest that antioxidant mechanisms (e.g., glutathione system) may be key in facilitating the distinct behavioral and physiological responses to stressors that characterize alternative stress coping styles. The results underscore how individual differences in stress coping style and redox state can influence behavioral responses to stress.

Introduction: Central regulation of energy homeostasis is essential for balancing lipid storage and reproductive investment; however, the hypothalamic factors governing this trade-off remain incompletely defined in birds. Neurosecretory protein GM (NPGM), an 83-amino acid hypothalamic factor, was investigated for its role in energy allocation during sexual maturation in Japanese quail (Coturnix japonica). Methods: Male and female quails at the onset of sexual maturation received chronic intracerebroventricular administration of NPGM for 13 days via osmotic pumps, during which their body mass, food intake, and water intake were monitored daily. At the endpoint, peripheral tissue and muscle masses, serum metabolite levels (glucose, fatty acids, triglycerides, testosterone, and 17{beta}-estradiol), hepatic triglyceride content, and gene expression profiles of hypothalamic feeding/reproductive genes and hepatic/adipose lipid metabolic genes were evaluated. Results: NPGM increased subcutaneous and abdominal fat in both sexes and was associated with suppressed gonadal maturation, as indicated by reduced testicular mass relative to body mass and lower testosterone levels in males, as well as a trend toward reduced ovarian mass and lower 17{beta}-estradiol levels in females. Sex-dependent metabolic phenotypes emerged: males exhibited increased body mass gain, hyperphagia, elevated water intake, enlarged liver, pancreas, and heart, higher serum and hepatic triglyceride levels, increased hepatic SCD1 expression, and reduced hepatic CGI-58, PPAR{gamma}, SLC2A2, and CD36. In contrast, females showed fat accumulation without hyperphagia or hepatic triglyceride elevation, accompanied by reduced hepatic VTG2 and APOV1 and decreased adipose ATGL, LPL, and FATP. Hypothalamic AGRP expression decreased in males, whereas both NPY and AGRP decreased in females. Discussion: These findings demonstrate that central NPGM shifts energy allocation from reproduction toward lipid storage through sex-dependent endocrine and metabolic mechanisms, identifying NPGM as a neuroendocrine regulator of energy allocation during sexual maturation in Japanese quails.

Interactions between melanin-concentrating hormone (MCH) neurons and oxytocin neurons are crucial for parental care. Whole-cell patch-clamp recordings demonstrated that MCH inhibits paraventricular hypothalamic nucleus (PVN)-oxytocin neurons through activation of barium-sensitive inwardly rectifying potassium channels, potentially G-protein coupled inwardly rectifying potassium channels, and pup-directed aggression was positively related to loss of MCH neurons. Our findings offer a glimpse into the neural mechanisms underlying the evolutionary regulation of offspring caregiving and abuse in males.

In natural environments, animals face a trade-off between foraging and staying vigilant against predators, a conflict known to shape sensory processing and behavior through natural selection. Even within a species, this trade-off may be resolved differently depending on age, sex, or life history. To identify the neural mechanisms underlying visually-guided pursuit-avoidance trade-offs, we studied how mice responded to a sudden overhead threat while pursuing a moving, prey-like target near the ground. This paradigm let us quantify orienting decisions in adolescent and adult mice of both sexes. We found that adolescence is a key period when male and female mice begin to diverge in how they resolve this conflict. Manipulating the value of the pursued target during adolescence versus adulthood revealed that adolescence is also a sensitive period for shaping adult escape-to-shelter versus continue to approach target behavior. Notably, hunting experience gained specifically during adolescence caused males, but not females, to shift strategy: experienced adolescent males tended to uniquely shift towards a "no-go" (stay-near-Prey) strategy. All the other groups instead favored an active "go" strategy, repeatedly shifting between approaching target and running to shelter. All mice showed this oscillation between approaching target and escaping to a shelter to some degree, but hunting experience during adolescence most significantly shifted this balance between approach and escape for males.

Operant paradigms are powerful tools to quantify motivation and reward. Traditionally, operant conditioning research has been limited to food and drug reinforcers. Recent advances in commercially available operant equipment, however, allow for the quantification of social motivation. These operant assays are an improvement over commonly used social preference tasks, as they enable direct measurement of the effort and motivation driving social behavior. Based on a design by Venniro et al. (2020), the MedPC social operant boxes modify the traditional operant box setup for social interactions. The experimental rat can lever-press to raise a door for an interaction with a target rat behind a porous barrier. These social operant boxes have been widely adapted to test social behavior in adult and adolescent rodents and investigate how a range of conditions (e.g. stress, drug taking, etc.) affect social motivation. However, there is a gap in assessing maternal motivation for pups during the postpartum period, despite ample evidence that postpartum social behavior is highly relevant for offspring health outcomes. Here, we detail 3D-printed modifications to the standard Med PC social operant boxes to adapt the social target chamber to safely house neonatal pups. We have also developed testing protocols to assess motivation during the limited postpartum period. These data demonstrate that, with simple modifications to social operant chambers and testing protocols, the field can implement advanced behavioral approaches to directly assess maternal motivation.

Long-term opioid therapy is limited by analgesic tolerance and opioid-induced hyperalgesia, but the roles of genetic background, sex, and drug exposure remain unclear. We used 20 inbred strains from the Hybrid Rat Diversity Panel to examine thermal sensitivity, oxycodone analgesia, tolerance, and hyperalgesia-like changes following voluntary intravenous oxycodone or saline self-administration. Rats underwent tail-immersion testing before self-administration (Pre-SA) and after self-administration (Post-SA). Oxycodone analgesia was assessed using the percent maximum possible effect time course and the corresponding area under the curve. Pre-SA thermal sensitivity differed across strains and between sexes, and Pre-SA oxycodone analgesia also differed across strains. Oxycodone self-administration produced a sex-dependent increase in thermal sensitivity that was most evident in males. During Post-SA testing, oxycodone self-administering rats showed reduced analgesic responsiveness compared with saline controls, and the magnitude of this difference varied across strains. Within-strain Pre-SA-to-Post-SA comparisons identified tolerance-like reductions in several strains. Across strains and sexes, oxycodone self-administering rats showed a greater Pre-SA-to-Post-SA reduction in analgesic responsiveness than saline controls, consistent with analgesic tolerance. Total oxycodone intake was not associated with tolerance at either the strain-mean or individual-animal level. Heritability estimates were higher for thermal sensitivity and analgesia (H2 {approx} 0.28-0.40) than for changes in thermal sensitivity and tolerance (H2 {approx} 0.18-0.27). These findings demonstrate strain variation in thermal sensitivity and oxycodone analgesia, sex-dependent hyperalgesia-like effects, and reduced analgesic responsiveness following voluntary oxycodone intake.

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.

BackgroundThe maturation of the autonomic nervous system (ANS) has been suggested to play a crucial role in the development of emotion regulation and later psychosocial functioning. However, longitudinal evidence linking early autonomic development to long-term outcomes remains limited. This longitudinal study investigated the interplay between birth-related factors, early autonomic activity, and psychosocial outcomes across development. MethodsThe sample comprised 101 participants followed from two weeks to 14 years of age, with heart rate (HR) and vagally ediated heart rate variability (vmHRV) assessed at 2 weeks, 6 weeks, 3 months, 14 months, and 14 years. Linear models were used to examine associations between birth-related factors and early HR and vmHRV, as well as whether HR and vmHRV trajectories during the first 14 months predicted psychosocial outcomes at 5 and 14 years. ResultsMultiple birth-related factors significantly predicted HR and vmHRV at two weeks after birth. Moreover, flatter age-related increases in vmHRV and weaker decreases in HR during infancy predicted higher maternally reported psychosocial difficulties at 14 years in males only, with no such effects at 5 years or in females. ConclusionsThese findings underscore the importance of early autonomic maturation in shaping later psychosocial functioning, with effects on adolescent outcomes observed in males only. Early ANS trajectories may represent meaningful predictors of neurodevelopmental outcomes, highlighting their potential relevance for early identification of later psychosocial risk in a sex-specific manner.

Menstrual symptoms vary across the cycle, yet most research assumes a normative 28-day cycle with fixed phase durations, obscuring the physiological relevance of natural cycle variation. Using the mcPHASES dataset, we characterised cycle and phase length variation across 96 menstrual cycles from 37 participants, with ovulation timing estimated from daily urinary luteinizing hormone measurements using a Bayesian hierarchical model, and examined associations with daily symptoms in a subset of 64 cycles from 35 participants with complete symptom data. Twelve physical, mental, and behavioural symptom domains were modelled using Bayesian ordinal regression, with posterior uncertainty in phase-length predictors propagated via a measurement error framework. Total cycle length was not associated with daily symptom burden, except sleep disturbances. By contrast, phase length decomposition revealed systematic associations across multiple domains: longer menstrual phase length was broadly associated with greater symptom intensity spanning physical, gastrointestinal, affective, and sleep domains; longer luteal phase duration was associated with greater fatigue and more frequent headaches, but lower sore breast intensity and lower stress; and longer follicular phase duration and later ovulation were each associated with greater sore breast intensity and more frequent mood swings. These associations require knowledge of actual ovulation timing and cannot be recovered from cycle length alone, indicating that the common assumption of a fixed 14-day luteal phase introduces systematic misclassification of hormonal exposure. Daily symptom intensity was also predominantly person-specific, with cycle phase explaining little of the between-person variance across most symptoms. These findings indicate that calendar-based phase assignment is insufficient for research and clinical assessment of hormone-sensitive conditions, and that person-specific baselines, rather than population-level phase averages, are needed for clinically meaningful symptom monitoring.

Adolescence is a fundamental developmental period marked by dramatic socio-affective and physiological changes, including shifts in social behavior and maturation of underlying brain architecture. In girls, this period coincides with the onset of the pubertal transition, which fundamentally influences motivated social behavior and neurodevelopment. The present study examines age- and pubertal maturation-related changes in social motivational goals and hippocampal and motivation-related cortical structural development in adolescent girls (n=154) across five timepoints. Social motivational goals showed substantial variability of each subdomain across age and pubertal development. Specifically, all social goals showed linear increases across age and pubertal stage, whereas goals centered around developing social competency increased non-linearly across age. Our neurodevelopmental findings align with established research, revealing volumetric increases of the hippocampus, and cortical thinning of the medial orbitofrontal cortex (mOFC) and rostral anterior cingulate cortex (rACC) across age and pubertal stages. Collectively, these results highlight simultaneous change in endorsement and prioritization of different social motivational goals across adolescence, and they underscore the simultaneous shifts in structural development in regions supporting social motivation and broader socio-affective development. This research highlights the importance of fostering positive social experiences during this critical developmental stage, with implications for adolescent well-being and social development.

Motivational deficit is a prevalent symptom across a wide range of neurodegenerative and neuropsychiatric disorders. Despite its clinical importance, first-line treatments for these disorders fail to effectively treat this symptom domain. In animal models, motivation is typically assessed in the context of extrinsic reward, where reward is delivered for completing an effortful action. However, many motivated behaviours occur in the absence of a tangible reward and are instead driven by intrinsic motivation. Previous work has shown that an extrinsic motivation task (effort for reward (EfR)) and an intrinsic motivation task (effort based forage (EBF) task) show opposing responses to a range of pharmacological manipulations. However, it is not clear whether intrinsic and extrinsic motivation dissociate in the context of endogenous behavioural variation. We therefore investigated whether these tasks were sensitive to behavioural variation across three different strains of mice (C57Bl/6JJRi, 129S2/SvPasOrlRj and BALB/cJRi) and whether strain profiles diverged across tasks. Here, we found that BALB/c mice showed the lowest levels of foraging in the EBF task, indicative of a low intrinsic motivational state but showed the highest levels of high effort responding in the EfR task, indicative of a high extrinsic motivational state. These differences were not driven by an anxiety-related phenotype and were therefore indicative of a motivation phenotype divergence across tasks. This work highlights the importance of moving away from considering motivation on a single axis, as findings can diverge depending on the nature of the motivational process. This has important implications for both phenotypic interpretation and the development of treatments targeting motivational dysfunction.

BackgroundCircadian disruption is strongly associated with alcohol use disorder (AUD), but insight into the underlying brain-region and sex-specific mechanisms is limited. The function of the circadian clock gene Bmal1 within the striatum has been linked to alcohol drinking, yet its role within functionally distinct striatal subregions has not been systematically examined. MethodsWe deleted Bmal1 in medium spiny neurons of the dorsomedial striatum (DMS) or dorsolateral striatum (DLS). Male and female mice were tested for anxiety-like behavior, depressive-like behavior, and motor coordination. Voluntary alcohol intake was measured with an intermittent two-bottle choice paradigm, followed by sucrose preference and quinine-adulterated alcohol tests. To assess hormonal contributions, a subset of female mice underwent ovariectomy before behavioral testing. ResultsDeletion of Bmal1 in the DLS did not alter alcohol intake, alcohol preference, or quinine-adulterated alcohol intake in either sex. In contrast, DMS Bmal1 deletion significantly reduced alcohol consumption and alcohol preference in female mice, with no effect in males. These effects were not accompanied by changes in depressive-like behavior or motor coordination and were not explained by generalized reward changes, as sucrose preference was unaffected. Ovariectomy eliminated the effect of DMS Bmal1 deletion on alcohol intake, indicating dependence on ovarian hormones. ConclusionsThe DMS is a critical site at which Bmal1 regulates alcohol consumption in a sex-specific manner. These findings support an interaction between local circadian mechanisms and ovarian hormones in controlling alcohol drinking and highlight a potential target for sex-specific therapeutics in AUD.

INTRODUCTIONSex differences in mental health emerge during adolescence, a period marked by the onset and the establishment of menstrual cycle. However, is rarely examined how menstrual cycle regularity, a marker of hormonal function, modulates mental health. OBJECTIVEto analyse sex differences in mental health symptoms among adolescents considering the menstrual cycle regularity and sleep. METHODSA three-group design (female students with regular cycles/FR, n=77; with irregular cycles/FI, n=59; and male students/M, n=76) in a sample of Brazilian high-school adolescents (n=212; 14-18 years) enrolled in morning and full-time classes was used to test the hypothesis that mental health symptoms follow a graded pattern across these groups. RESULTSMean DASS-21 scores across all groups fell at or above the Mild severity threshold for mental health subscales. GLMs confirmed a monotonic gradient increase in group order (M[-&gt;]FR[-&gt;]FI) which was associated with higher scores on all outcomes (stress {beta}/step=4.33, p<.001; anxiety {beta}/step=4.08, p<.001; and depression {beta}/step=2.34, p=.010; model R{superscript 2}=.16, .13, .08 respectively). However, no differences were observed in sleep duration, social jetlag, chronotype, sleep quality, or sleep-debt. Then, a secondary analysis assessed sex-specific associations between socioeconomic status (SES) and mental health; higher SES was inversely related to stress, anxiety, and depression, being protective only in males (stress Males {beta}=-2.68, p=.011/Females {beta}=0.46, p=.614). CONCLUSIONThese findings support the reframing of menstrual irregularity not only as a reproductive health concern but also as a biological determinant of mental health risk in female adolescents, a vulnerability that sleep disruption and socioeconomic resources do not adequately explain.

Objective: To examine changes in the neural valuation of high- versus low-calorie stimuli following bariatric surgery and determine whether these changes relate to weight loss at 24 months. Methods: Adults undergoing bariatric surgery completed fMRI scans before surgery and at 4, 12 and 24 months post-surgery while performing the Becker-DeGroot-Marschak auction task to assess willingness-to-pay (WTP) for food stimuli. Linear mixed-effect models tested longitudinal changes in WTP-related blood oxygen level-dependent (BOLD) associations and their interactions with total weight loss at 24 months. Results: WTP for high-calorie foods decreased significantly after surgery, whereas valuation of low-calorie foods remained stable. At 4 months, WTP-BOLD associations for high- versus low-calorie stimuli were enhanced within the frontoparietal control network and right lateral orbitofrontal cortex relative to pre-surgery. These early postoperative changes did not correlate with 24-month weight loss. Instead, greater 24-month weight loss correlated with both pre-surgical and long-term changes (24 months versus pre-surgery) in WTP-BOLD associations within the precuneus, inferior parietal cortex and visual cortex. Conclusion: Bariatric surgery induces early reductions in the valuation of high-calorie foods, potentially through enhanced cognitive control and aversive processing. However, long-term weight-loss success appears more strongly related to trait-like neural differences in self-referential and attentional processing.

It is increasingly appreciated that B cell populations in the brain shift during aging and Alzheimer's Disease (AD), contributing to neuroinflammation and cognitive decline. Though the underlying mechanisms remain unclear, biological sex is likely a key regulator since differences in B cell antibody responses are one of the most well conserved sex differences in immunology. Sex differences in B cell subtypes and antibody classes are significant because they drive sexually dimorphic immune responses and subsequent disease susceptibility. Despite extensive work evaluating the effects of gonadal hormones on B cells, the effects of aging and AD pathology, and the contributions of sex chromosomes are understudied. We evaluated B cell subtypes in the brain and bloodstream in both adult and 5xFAD mice via flow cytometry and antibody levels in the cortical brain region of both groups via ELISAs. We found sex differences mediated by both sex chromosomes and the gonadal hormone environment; these differences were primarily involved in antibody class-switching.

Background: Acute cortisol responses to psychosocial stress vary substantially across individuals, yet how this variability is reflected in post-stress resting-state functional connectivity (rsFC) remains unclear. Although prior work has linked stress-related endocrine responses to brain connectivity, studies have been limited by small samples, region-of-interest approaches, or a sole focus on group-level analyses. Here, we investigated whether acute cortisol increase is associated with, and can be predicted from, whole-brain post-stress rsFC. Methods: We analyzed 339 healthy participants from two ScanSTRESS datasets using complementary inferential and predictive approaches. First, we used the Network-Based Statistic (NBS) to identify connected rsFC networks associated with acute cortisol increase, controlling for age, site, and sex/hormonal status. Second, we predicted participants' acute cortisol increase from their connectivity patterns using NBS-Predict and Connectome-Based Predictive Modeling (CPM). Together, we examined the cortisol-rsFC relationship at the population and individual levels. Results: Greater cortisol responses were associated with lower post-stress rsFC within a significant distributed network comprising 258 connections among 78 regions, centered on thalamic nuclei and pallidal regions and extending to default-mode, limbic, orbitofrontal, and cerebellar regions. Sex-stratified analyses revealed a significant negative association only in females, but formal sex-difference contrasts were not significant. NBS-Predict and CPM yielded modest but significant out-of-sample prediction, with predictive networks converging on subcortical and posterior cingulate regions. Conclusions: Post-stress rsFC carries convergent inferential and predictive information about individual HPA-axis reactivity. Stronger cortisol responses were characterized by reduced connectivity within a distributed subcortical-cingulate network, supporting a network-level perspective on neural-endocrine coupling following acute stress.