Hormones and Behavior

Despite the well-established health benefits of exercise, adherence to physical activity remains low, highlighting the need to identify biological factors that regulate the initiation and persistence of exercise behavior. Here, we tested whether ovarian hormone state at the onset of voluntary wheel running (VWR) influences both immediate and long-term exercise behavior in female rats. Females that initiated VWR during proestrus (Pro) ran farther, spent more time running, and ran at higher speeds on the first day of wheel access than females initiating VWR outside of Pro. Remarkably, initiating VWR during Pro also produced persistent increases in running distance, duration, speed, and escalation across subsequent weeks, despite normal cycling through other estrous phases. In contrast, exogenous estradiol (E2) administered at VWR initiation did not alter day-1 behavior, but increased running distance and duration across subsequent weeks without affecting running speed or escalation. To determine whether dorsal striatal dopamine contributes to these effects, we inhibited the substantia nigra (SN) to dorsolateral striatum (DLS) pathway on the first day of VWR. This manipulation reduced the immediate and long-term effects of initiating VWR during Pro on running duration and distance but not speed or escalation. These findings identify behavioral initiation as a critical window during which hormones and nigrostriatal signaling influence future engagement in physical activity. Furthermore, analysis of individual components of VWR architecture reveals that distinct features of VWR behavior can be dissociated mechanistically and thus could be used to investigate separate motivational processes underlying physical activity.

Combined oral contraceptives (OCs), containing synthetic estrogen and a progestin such as levonorgestrel (LVNG), are widely used, and up to 10% of users experience adverse mood states and increased depression risk. It is well-established that OCs modulate the hypothalamic-pituitary-adrenal (HPA) axis and blunt the cortisol responses to acute stress. This interaction with stress regulatory pathways is one mechanism by which OCs might impact mood. Here, we used a mouse model of OC exposure (ethinyl estradiol (EE) + LVNG) to investigate how OCs affect regulation of the diurnal CORT cycle and stress-related signaling in the dorsal and ventral hippocampus and paraventricular nucleus of the hypothalamus (PVN). We found that EE+LVNG did not alter basal corticosterone (CORT) levels, but impaired glucocorticoid receptor (GR) - mediated negative feedback in the dexamethasone suppression test. Molecular analyses revealed distinct, region-specific effects. In the dorsal hippocampus, EE+LVNG enhanced glucocorticoid receptor (GR)-dependent gene signaling and prolonged Fkbp5 induction. In the ventral hippocampus, EE+LVNG enhanced mineralocorticoid receptor (MR)-dependent signaling and reduced stress-induced corticotropin-releasing factor expression. In the PVN, EE+LVNG reduced MR expression and modulated MR-dependent signaling. Together, these findings demonstrate that chronic OC exposure disrupts GR- and MR-dependent regulation across stress-related brain regions and impairs glucocorticoid feedback, providing potential mechanisms by which OCs blunt stress responsivity, modify long-term HPA-axis function, and increase susceptibility or resilience to stress and depression.

Background: Androgen deficiency in males is associated with reduced motivation, fatigue, and decreased goal-directed behavior, yet the neural mechanisms underlying these changes remain poorly understood. Dopamine signaling within the nucleus accumbens (NAc) plays a central role in regulating effort-based decision making. Here, we tested the hypothesis that loss of testicular hormones alters mesoaccumbal dopamine function to increase sensitivity to effort-related costs. Methods: Male mice underwent orchiectomy (ORX) either before puberty onset or in adulthood. Effort-based decision making was assessed using a progressive ratio 1 closed economy (PR1-CE) task. Dopamine-related function was assessed using systemic haloperidol administration and high-performance liquid chromatography to measure dopamine and metabolites, while whole-cell recordings were used to assess intrinsic excitability of NAc spiny projection neurons (SPNs). Results: ORX increased sensitivity to effort costs, reflected by a shift toward energy-efficient responding while maintaining overall food intake. These behavioral changes were accompanied by reduced responsiveness to haloperidol. Postpubertal ORX increased dopamine content and reduced metabolite-to-dopamine ratios in the NAc, consistent with reduced dopamine turnover, whereas prepubertal ORX did not affect dopamine measures. Prepubertal ORX selectively reduced excitability of NAc core D1R+ SPNs, while postpubertal ORX increased excitability across both D1R+ and D1R- populations. Conclusions: Androgen depletion increases effort cost sensitivity and is associated with alterations in mesoaccumbal circuit function. Although behavioral effects were similar following pre- or postpubertal ORX, distinct neurochemical and cellular adaptations were observed, suggesting developmental timing influences neural adaptations to androgen depletion. These findings provide insight into neural mechanisms linking androgen deficiency to motivational deficits.

Hormonal regulation of patch-leaving decision-making remains poorly understood. Here, young adult male and female Long-Evans rats were tested in a patch-leaving task before and after orchiectomy (ORCH), ovariectomy (OVX), or sham surgery, and were subsequently assessed in an impulsive-choice task. Patch leaving was measured under long- and short-travel conditions. Before surgery, males showed longer overstay than females during long-travel sessions, whereas no clear sex difference was detected during short-travel sessions. After surgery, orchiectomy did not produce a uniform shift in patch leaving but selectively disrupted the progressive reduction in overstay that normally emerged across repeated long-travel sessions. By contrast, ovariectomy produced weaker effects and did not reveal a comparably robust change in female patch leaving. Spatial and idle occupancy analyses showed that gonadectomy also altered within-patch behavior, with orchiectomy most strongly increasing idling-related measures in males, whereas ovariectomy more strongly redistributed female patch occupancy. Estrous stage did not significantly organize pre-surgical female overstay. Greater impulsive choice was associated with smaller post-surgical reductions in long-travel overstay in the unadjusted analysis. Together, these findings indicate that testicular hormones selectively support patch-leaving adaptation under high travel cost.

Ambiguity represents a form of uncertainty in which outcome probabilities cannot be explicitly learned, making decisions dependent on emotional states and cognitive biases. Early-life stress (ELS) increases the risk of adverse mental and physical health outcomes and alters affective processing and learning. ELS may thus affect how ambiguous information is processed, which may depend on interactions with adulthood stress (AS) and mechanistically on bioenergetic mechanisms mediated by top-down cognitive control systems within the prefrontal cortex (PFC). The present study investigated the effects of AS in rats exposed to early maternal separation (MS), a rodent model of ELS, on a task assessing cognitive bias, together with putatively accompanying alterations in PFC mitochondrial function. Cognitive bias was assessed using an ambiguous cue task (ACT) in MS and non-separated control rats tested at baseline and following repeated unpredictable mild stress during adulthood. MS did not affect baseline cognitive bias but increased response latencies. Following AS, control animals showed a significant negative shift in cognitive bias, whereas MS animals were resistant to this shift. MS was also associated with greater PFC mitochondrial respiratory capacity and uncoupling of oxidative phosphorylation following AS. These findings suggest that ELS is associated with a recalibrated phenotype that buffers against the affective consequences of later stress. Enhanced PFC mitochondrial bioenergetics may underlie this resilience, highlighting the importance of developmental context in shaping affective-cognitive responses to stress.

Voluntary physical activity is a highly motivated behavior with important implications for physical and mental health, yet the neural and endocrine mechanisms underlying motivation to exercise remain poorly understood. In contrast, motivation for sugar/palatable foods, drugs, and sex has been extensively characterized using operant paradigms. Here, we describe a novel progressive ratio operant task to measure motivation to run, independent of running ability. Using female Long Evans rats, which exhibit robust voluntary running behavior, we validated this paradigm by applying a manipulation well known to enhance the motivation to run: calorie restriction. Calorie-restricted animals exhibited increased operant responding to gain access to a running wheel, thus demonstrating heightened motivation for exercise. More specifically, calorie-restricted rats completed more ratios, reached a higher breakpoint in the progressive ratio task, ran more, and spent more time in the operant chamber. We did not observe any effects of calorie restriction on the estrous cycle or steroids (e.g. corticosterone, testosterone) in the blood or brain. Importantly, our task dissociates the motivational drive for physical activity from the ability to perform the physical activity itself, providing a new paradigm for studying the neural and endocrine mechanisms that regulate exercise motivation.

Estrogen is an essential hormone that critically impacts bodily and brain functions, supporting learning, memory, and motor activities. A decrease in estrogen levels is associated with cognitive decline and motor dysfunction, such as muscle weakness. While conventional hormone replacement treatments (HRT) exist, those have limitations and potentially severe side effects. NAP (davunetide) is the smallest neuroprotective peptide site of activity-dependent neuroprotective protein (ADNP), a master regulator of cognition, essential for brain formation. It is known that NAP restores ADNP activity in cases of deficiency and it has already shown potential in preventing cognitive impairment, protecting against tauopathy, and improving motor function in various animal models and in clinical trials. Based on the dynamic regulation of ADNP by the estrous cycle and its involvement in steroidogenic pathways, we hypothesize that NAP may restore ADNP activity and thus serve as an alternative to conventional hormonal treatments. To test this, 3-month-old female ICR mice underwent bilateral ovariectomy (OVX) or Sham surgery and received daily intranasal administration of NAP, estrogen, or vehicle. Results showed a significant reduction in weight-normalized forelimb grip strength in the OVX model. Daily administration of NAP or estrogen resulted in intermediate grip strength levels that did not statistically differ from either the Sham control or untreated OVX groups. Interestingly, grip strength was the only test that yielded significant results, and no significant differences were observed in the Novel Object Recognition (NOR) test or computed tomography (CT) scans. These findings suggest that NAP may effectively prevent the loss of physical force production typically seen following ovarian hormone depletion, presenting a viable, non-hormonal candidate strategy for managing musculoskeletal symptoms. We hypothesize that the lack of significance in other parameters was due to soy-derived phytoestrogens in the diet, which may have exerted a systemic estrogenic effect that masked the expected physiological phenotypes typically observed in OVX models. Future replication using phytoestrogen-deficient food is required to isolate the specific neuroprotective and musculoskeletal effects of NAP from dietary influence and clarify the broader therapeutic benefits of NAP.

IntroductionAnorexia nervosa (AN) is more prevalent in women than men, although rates in men are rising. Animal models can provide insight into whether this differential prevalence is rooted in biological mechanisms, but prior studies have yielded conflicting findings. Using the activity-based anorexia (ABA) model, we previously demonstrated that female mice exhibit distinct vulnerable and resilient phenotypes. Here, we use this phenotypic framework to investigate sex differences in ABA susceptibility. MethodsWe tested young adult male C57BL/6N mice using the same ABA protocol used to test age-matched C57BL/6N females. Individual differences in daily bodyweight, food intake, water intake, and wheel running were analyzed and compared across sexes. ResultsMales exhibit the same vulnerable and resilient phenotypes as females, with no sex difference in the proportion of mice exhibiting each phenotype or the repertoire of behaviors characterizing them. In both sexes, vulnerable mice exhibit catastrophic weight loss driven by excessive light cycle running, while resilient mice exhibit weight stabilization driven by adaptive changes in consumption. Running during the feeding window revealed that vulnerability is not driven by a decision to run instead of eat in either sex. ConclusionsABA models adaptive and maladaptive responses to food restriction in both sexes. Behavioral responses to starvation are similar across sexes, suggesting that sex differences in AN prevalence may be driven by stronger sociocultural pressures faced by women to lose weight.

Birth occurs during a sensitive period in brain development wherein hormones facilitate the dramatic shift in physiology that accomplishes the transition to extrauterine homeostasis. The surge in birth signaling hormones is abridged in cases of delivery by cesarean section (CS), which accounts for 32% of all births in the U.S. Epidemiological studies have associated birth via CS with increased risk of obesity in later life. Here, we sought to investigate this association using an experimental preclinical animal model, the prairie vole. Subjects were delivered either via vaginal delivery (VD) or CS and then cross-fostered. CS delivery led to increased body weight across development, which could be prevented with hormone rescue of oxytocin (OXT) and arginine vasopressin (AVP), delivered to neonates immediately after CS. This weight gain could not be attributed to differences in birth weight, parenting, food consumption, or thermoregulation; however, CS subjects moved slower than VD subjects, which hormone rescue reversed. Hormone rescue also reduced adiposity in adulthood among CS subjects. The dopamine system was dysregulated in the caudate/putamen of CS offspring, suggesting a neural mechanism for the decreased locomotion. Hormone rescue of CS neonates restored dopamine synthesis in the caudate/putamen and increased spontaneous locomotor activity. These findings suggest CS can lead to increased weight gain in part through a reduction of locomotion driven by long-lasting changes in striatal dopamine regulation, all of which can be prevented by treating CS neonates with a single peripheral administration of two birth-signaling hormones, OXT and AVP.

Breeding female mice represent an essential but often overlooked workforce sustaining biomedical research. Despite their central role, the physiological and behavioral consequences of repeated reproductive cycles have been poorly characterized, in part because breeding animals fall outside the primary focus of laboratory animal welfare efforts, and in part because meaningful welfare readouts for laboratory rodents remain an active area of research. Here we report findings from an exploratory phenotypic study designed to capture a composite picture of maternal health in female mice of two commonly used inbred strains, BALB/cByJ and C57BL/6J, exposed to one, two, or four consecutive cycles of pregnancy and lactation, with age-matched virgin females as controls. Assessments were conducted during the final lactation period and in the five weeks following weaning, spanning behavioral, metabolic, and physiological readouts selected for their known sensitivity to reproductive or environmental challenge. Repeated reproduction altered maternal physiology, most clearly in bone microstructure, which showed progressive and dose-dependent changes across parity levels, and more subtly in body mass, energy balance, and glucose homeostasis. Behavioral readouts of maternal motivation, by contrast, remained largely stable across reproductive load. Strain differences were pervasive, underscoring that reproductive adaptation is not uniform across standard laboratory models and cautioning against generalizing from a single strain. Together, the data suggest that mouse dams demonstrate considerable resilience under intensive breeding conditions, while also highlighting that breeding shapes the maternal body in ways that accumulate across reproductive cycles and deserve greater scientific attention.

Although female rats are typically less aggressive than male rats, lactating females will vigorously defend their nests and pups against an intruder. Much attention has been directed at the consequences of this aggression on the intruder and less on the consequences for the mother and her subsequent interactions with her pups. Here, we exposed resident Sprague-Dawley dams to the resident-intruder paradigm twice daily for five consecutive days, beginning when the dam's (RES) pups were 7 days old, to assess social stress effects on maternal behavior and neurobiology. Controls were dams that had time-matched (TMC) separation from their pups but were not exposed to intruders, and naive moms which were never separated nor exposed to an intruder (CTL). We assessed the dam's subsequent behavior and interactions with her pups on Day 1 and Day 5, and Fos expression after Day 5 in select regions of the prefrontal cortex, amygdala, hypothalamus and periaqueductal gray of the midbrain. In separate cohorts, after pups were weaned, the dams underwent restraint stress and plasma corticosterone assayed. PCA analysis of the dam's behaviors identified three components: normal self-focused behaviors; nurturing behaviors and rough non-nurturing behaviors. Relative to CTL, RES dams exhibited more disrupted behaviors towards their pups, including, rough transport, stepping on pups, and flinging/tossing pups around the cage. In contrast, TMC Dams showed some, but fewer changes relative to CTL, suggesting that separation from pups alone does not account for all disrupted behavior in RES dams. The bulk of these behavioral effects occurred in the first 5-10 min after reunion with the pups and were seen on both the first and fifth day of testing. Of the brain regions examined, the prefrontal cortex was activated by both the defeat/intruder stress (RES) and separation stress (TMC), whereas the dorsal PAG was activated specifically by the defeat/intruder stress. The medial and basolateral amygdala exhibited differential neuronal activity between the RES defeat/intruder-exposed dams and the other two groups. The RES moms exhibited an insufficient adrenocortical response to acute restraint stress. The results suggest that amygdala-dPAG activity is important for dissociating disrupted maternal care in RES (due to defense of the nest against an intruder) from simple pup separation, both of which activate the mPFC. The experience of repeatedly defending the nest may induce subsequent disruptions in HPA responses. The amygdala-dPAG pathway may regulate aspects of stress and emotional regulation exhibited by mothers who defend their offspring against intruders.

Rationale: Early life stress (ELS) is acknowledged to underlie cognitive and emotional abnormalities linked to stress-related mood disorders. ELS can lead to persistent biases in how uncertain feedback is processed to affect the flexibility of decision-making. Objectives: (1) To investigate the effects of ELS on the flexibility of rats trained on a serial probabilistic reversal learning (PRL) task involving spurious positive and negative feedback. (2) To elucidate the involvement of the stress hormone corticosterone and the noradrenergic and serotonergic systems in modulating how ELS affects PRL. Methods: Male and female rats were intermittently separated from maternal care on postnatal days five to nineteen, inclusively. As adults, the same rats were trained on a deterministic reversal learning task involving certain rewarded or non-rewarded outcomes followed by a PRL task where correct and incorrect responses were rewarded on 80% and 20% of trials, respectively. Dose-dependent effects of the beta-blocker, propranolol, selective serotonin reuptake inhibitor, citalopram and corticosterone were subsequently determined. Results: ELS resulted in an increased responsivity to feedback, specifically in males making more win-stay responses following a reward, that was associated with an increased punishment learning rate. In both control and MS rats, propranolol increased feedback sensitivity, but delayed updating following a rule switch. In contrast, neither citalopram nor corticosterone significantly affected reversal learning. Conclusions: ELS is sufficient to cause persistent changes in how feedback is processed by male rats on a reversal learning task. Activation of beta-adrenergic receptors may be necessary for updating learned associations during decision-making involving uncertain feedback.

Adrenal chromaffin cells are key effectors of the sympathoadrenal response and play a central role in the organisms adaptation to environmental and physiological challenges. While cholinergic and pituitary adenylate cyclase-activating polypeptide (PACAP)-dependent mechanisms have long been recognized as major regulators of catecholamine secretion, increasing evidence indicates that connexin-mediated gap junctional communication provides an additional and highly dynamic level of control. Whether early-life experience modifies the adult capacity of chromaffin-cell networks to undergo stress-induced connexin remodeling remains unclear. Here, we examined adrenal medullary connexin expression in adult rats exposed to neonatal maternal separation (MS; 3 h daily, postnatal days 2-15) and later challenged with an 8-day unpredictable mild stress (UMS) protocol. Under basal adult conditions, MS did not produce an overt change in adrenal medullary Cx36 or Cx43 immunoreactivity relative to animal-facility-reared controls. In contrast, UMS increased connexin immunoreactivity in the adrenal medulla, and this response was amplified in animals with a history of MS. MS+UMS animals also displayed enhanced corticosterone responses to acute restraint stress. These findings suggest that neonatal MS does not impose a constitutively altered adult chromaffin-cell phenotype, but instead primes the future stress responsiveness of adrenal medullary connexin remodeling. We propose that chromaffin-cell gap junctions represent a substrate sensitive to stress history, through which developmental experience may influence sympathoadrenal and endocrine adaptation in adulthood.

Top down signaling from the cortex to the hypothalamus is critical to link cognitive and emotional processing to homeostasis and motivation. This study investigates signaling from the medial prefrontal cortex (mPFC) to the posterior hypothalamus (PH), a region that modulates endocrine and autonomic stress responses and motivated behaviors. The function and anatomy of this circuit was examined with patch clamp electrophysiology and mapping studies in male and female rats. Spontaneous firing properties of PH neurons were determined in a cell-type specific manner by combining a transgenic glutamic acid decarboxylase-Cre rat with Cre-dependent colorswitch virus to determine postsynaptic cell-type identity. Overall, PH neurons were more excitable in females compared to males and, in both sexes, data indicated tonic inhibition within the PH, with significantly greater inhibition in males. Using Channelrhodopsin-assisted circuit mapping to query the mPFC-PH circuit, we found that a majority of PH neurons received input from the mPFC and mPFC synapses targeted glutamatergic cells over GABAergic PH cells. Retrograde tracing revealed more PH-projecting neurons in females, specifically within the tenia tecta and infralimbic regions of the mPFC, with significantly more stress-activated PH-projecting cells in the female prelimbic cortex. Anterograde tracing revealed, surprisingly, no sex differences in mPFC presynaptic terminal density in the PH, despite more PH-projecting cell bodies in the female mPFC. These data help to elucidate the sexual divergence in cortical-hypothalamic signaling and how cognitive and emotional information from the prefrontal cortex may differentially regulate homeostasis and motivation between sexes. Significance StatementNeural signaling between the prefrontal cortex and the hypothalamus is important for maintaining homeostasis, particularly during contextual challenges such as stressors. Here we find multiple aspects of sex-specific organization and neurophysiology in this circuitry. Excitatory inputs from the medial prefrontal cortex target both excitatory and inhibitory neurons within the posterior hypothalamic nucleus in both sexes. However, there are sex differences in the number of stress-activated neurons in the prefrontal cortex that innervate the posterior hypothalamus, as well as differences in hypothalamic inhibitory signaling and estrous cycle-dependent effects on neuronal excitability. Altogether, these data suggest that organizational, synaptic, and hormonal factors may contribute to sex-specific behavioral and physiological integration.

Purpose: Gonadotropin releasing hormone (GnRH) agonists are clinically used to delay pubertal progression by suppressing the hypothalamic-pituitary-gonadal (HPG) axis. While GnRH agonists have long been used clinically, the developmental characterization of HPG axis suppression during puberty remains incompletely understood. Thus, we examined the effects of GnRH receptor agonism in juvenile rats. Hypothesis: Sustained GnRH receptor agonism will result in lower gonadal mass, blunt peripheral pubertal landmarks, and alter hormonal signaling dynamics within the HPG axis. Methods: Animals received a single injection of extended-release leuprolide acetate depot (LA) or vehicle control on postnatal day (PND) 23. Animals were assessed for body mass and peripheral markers of puberty. On PND 44, animals were euthanized and tissues were evaluated to assess additional markers of pubertal maturation, pituitary gene transcript levels, and hormone concentrations in serum and gonads. Results: In females, LA treatment resulted in a smaller gonad size, increased body mass, and less vaginal openings. In males, LA treatment resulted in smaller gonads but did not significantly alter body mass or preputial separation. In the pituitary, LA-treated rats had lower Gnrhr, Fshb, and Lhb transcript levels regardless of sex, while females exhibited higher Cga and Nr5a1. Serum FSH and ACTH were lower in LA-treated animals, and treated females also had lower progestins and androstenedione, and higher LH. Conclusions: LA treatment reduced aspects of pubertal maturation and HPG axis output, with sex specific outcomes. These findings highlight the need for integrated, multi-level approaches to understand how altered GnRH signaling impacts pubertal and long-term physiology.

To attract mating partners, female mammals communicate their reproductive status through one or multiple sensory modalities, providing redundant or complementary information. Chimpanzees (Pan troglodytes) are an excellent model for studying multimodal communication. Exaggerated sexual swellings of females serve as a visual proxy for ovulation but increased male mating interest during maximum swelling suggests that olfactory cues may pinpoint fertility more accurately than the swelling alone. Here, we combined gas chromatography-mass spectrometry, hormonal analyses, and bioassays to examine (1) whether chemical composition of female anogenital odours changes during the fertile period, and (2) whether males are able to detect these changes. Our results suggest that, in addition to prominent olfactory changes associated with swelling stages, chemical cues provide complementary information regarding the timing of the fertile window. These changes, however, are minor compared to those related to swelling stages. Male behavioural responsiveness in bioassays was too low to draw conclusions regarding their ability to detect these subtle shifts when presented with a chemical cue only. Overall, our findings support the existence of a multimodal fertility cue in chimpanzees, wherein visual signals are complemented by subtle olfactory changes indicating the timing of the fertile period.

Motivation fluctuates across the menstrual cycle, yet the computational mechanisms underlying these changes remain unclear. We tested whether hormonally defined cycle phases selectively alter distinct components of effort-based motivation in naturally cycling women (n=51), who completed an effort-reward decision-making task and an effort psychophysics task in both the late-follicular and mid-luteal phases, alongside electrocardiography and ecological momentary assessment. Hierarchical Bayesian modelling revealed that the anticipated cost of physical effort (effort sensitivity) was selectively elevated in the mid-luteal phase, with no corresponding change in reward sensitivity. The luteal increase in effort sensitivity was attenuated in women who entered that phase after days of higher affective valence and arousal, indicating that positive affective state buffers cyclical motivational vulnerability. Complementing these findings, phase-related individual differences in effort the mapping between objective and perceived effort (effort differentiation) were not different by phase, but were moderated by heart rate variability and momentary affective states, revealing stable person-level variation in how the cycle shapes effortful experience. Together, these results identify effort sensitivity as a specific computational mechanism of cyclical motivational change, with implications for understanding the elevated burden of cycle-related psychiatric conditions across the female reproductive lifespan.

Polycystic Ovarian Syndrome (PCOS) is a complex endocrine disorder characterised by hyperandrogenism, oligo- or anovulation, and polycystic ovaries. Endocrine dysfunction in PCOS disrupts both hormonal and neurotransmitter balance, contributing to the psychological distress frequently reported by affected individuals. Although hormonal imbalances have been associated with memory impairments, their specific contribution to cognitive dysfunction in PCOS remains incompletely understood. In this study, we investigated the impact of PCOS on the hippocampus, a brain region critical for memory formation and highly sensitive to sex steroid modulation. A dehydroepiandrosterone (DHEA)-induced PCOS mouse model was employed to assess anxiety-like behaviour, locomotion, and memory. In the open field test (OFT), DHEA-treated mice spent significantly less time in the central zones and travelled a shorter total distance compared with controls, indicating increased anxiety-like behaviour. DHEA treatment also resulted in significantly impaired performance in both the object location test (OLT) and novel object recognition test (NORT), as reflected by a reduced discrimination index. Analysis of hippocampal immediate early gene expression using qRT-PCR revealed altered transcription of memory-related markers, including downregulation of Npas4 and Grin2a, and upregulation of Grin1, Arc, Egr1, and Egr2. Collectively, these findings suggest that elevated androgen levels induce anxiety- and depression-like behaviours and impair cognitive function, including spatial, recognition, and motor learning abilities, in PCOS. Our results further indicate that disrupted cortex-hippocampus communication may underlie these cognitive deficits, underscoring the importance of evaluating memory and cognitive health in women with PCOS to support brain health and overall well-being.

Within species, male testosterone is often linked to mating competition and paternal care, suggesting that sex differences in endogenous testosterone values across mammals may covary with broader reproductive strategies. Using a structured literature search, we compiled 63 studies, spanning 31 non-human species and 9 human populations, reporting endogenous, non-experimentally manipulated testosterone values for both adult males and females within the same population and context. From these studies, we calculated male-to-female testosterone ratios, and analysed these data using Bayesian phylogenetic multilevel models. We tested whether testosterone dimorphism was associated with paternal care and sexual size dimorphism while accounting for sampling matrix, assay method, breeding context, and wild versus captive setting. Across non-human mammals, neither paternal care nor sexual size dimorphism (indexing competition) showed a clear association with testosterone ratios, and the same pattern emerged in the primate-only subset. By contrast, sampling matrix was consistently associated with testosterone dimorphism across all analyses, with lower male-to-female ratios in non-blood than in blood-based measures. In primates, testosterone ratios were also lower in captive than in wild populations, although this pattern was not clearly supported in the broader non-human dataset. In the human-only analysis, testosterone ratios did not clearly differ between industrialized and small-scale societies, whereas the matrix effect remained evident. Overall, our results suggest that sampling matrix is a major source of variation even for ratio-based measures, highlighting the need for caution when inferring between-species endocrine differences from studies using different substrates. More broadly, directly comparable, non-experimentally manipulated testosterone data for both sexes remain rare across mammals, limiting comparative inference.

The lactational period requires substantial metabolic and behavioral adaptations, and more than 70% of mothers report weight concerns and attempt weight loss by four months postpartum. Nevertheless, how distinct restrictive paradigms during lactation alter maternal behavior, and the extent to which associated neurochemical changes modulate these behaviors, remains poorly understood. In the current study, we modeled restrictive diets in lactating rats to evaluate caregiving behavior and its relationship to amygdalar redox status. Intermittent fasting (IF) and caloric restriction (CR) administered to lactating Wistar dams from postpartum day 0 to day 28 impaired maternal care, evidenced by delayed pup retrieval, reduced nest building, and decreased nursing frequency relative to ad libitum-fed controls. Both diets reduced body and adipose tissue weight, and energy efficiency. IF and CR increased impulsivity-like phenotype: CR doubled open-arm exploration in the elevated plus maze; IF and CR increased center-zone exploration in the open field by three- and two-fold, respectively; IF doubled time in the light-dark box light compartment. A composite maternal behavioral score showed impairment in dams in both IF and CR groups. At the neurochemical level, both diets reduced amygdalar superoxide dismutase activity, which correlated negatively with the maternal behavioral score. Both restrictive diets produced an underweight phenotype with weakened dam-pup interactions and increased impulsivity. These behavioral changes co-occurred with amygdalar redox imbalance, which correlated with the severity of maternal impairment. Overall, the study refines understanding of the nutritional and behavioral consequences of dietary restriction in lactation and implicates disrupted redox homeostasis as a plausible mechanism.