Staging of the estrous cycle and induction of estrus in experimental rodents: an update

Activation of anoctamin-1 calcium-activated chloride channels reduces voluntary alcohol consumption in rats

Repeated episodes of binge drinking can lead to an alcohol use disorder, yet the underlying pharmacological mechanisms are still not fully understood. Nevertheless, emerging evidence indicates that Ca2+-dependent signaling effectively reduces alcohol consumption without affecting water intake. Therefore, activating anoctamin1 (ANO1), a Ca2+-activated chloride channel and a component of Ca2+-dependent signaling, can similarly decrease alcohol drinking while maintaining normal water intake. This study investigates how activation of ANO1 channels with EACT affects voluntary alcohol consumption in male and female Sprague-Dawley rats using the intermittent alcohol access method in a two-bottle choice paradigm. Rats were trained to drink 7.5 % ethanol or water for four weeks before administering either EACT (2.5, 5, and 10 mg/kg). Afterward, their alcohol intake, preference, and water intake were systematically recorded 2 and 24 h after exposure to water and 7.5 % ethanol solution. The results indicated that female rats consumed more alcohol than males. Furthermore, activating ANO1 channels with EACT significantly decreased alcohol intake and preference in males, only at the 5 mg/kg dose; in females, this effect was observed as a linear response at both the 5 and 10 mg/kg doses, highlighting distinct sex-related differences. Additionally, the inhibitory effect of EACT on alcohol consumption was associated with increased water intake in females, suggesting a potential influence of EACT on thirst homeostasis. Collectively, these findings highlight the differential effects of EACT on alcohol intake, preference, and water intake based on sex, and underscore the complexity of consummatory behavior mechanisms.

Evaluating spironolactone monotherapy against combined treatment with metformin in rat PCOS model

Polycystic ovarian syndrome (PCOS) is a common gynecological disorder with multifactorial pathogenic risk factors. Combination therapy with metformin and thiazolidinedione derivatives is frequently used, but its synergistic effects have not been thoroughly evaluated. This study aims to compare the therapeutic efficacy of low-dose spironolactone (LDS) at 0.25 mg/kg for 28 days, metformin at 500 mg/kg for 28 days, and a combination of LDS and metformin, against a letrozole (1 mg/kg/day) and 0.5 % carboxymethylcellulose (CMC)-induced PCOS rat model. The study involved five groups of laboratory animals: Group I (Healthy control), Group IIa (Disease control), Group IIb (Metformin), Group IIc (LDS), and Group IId (Metformin + LDS). Therapeutic efficacy was evaluated based on phenotypic, hormonal, and genotypic determinants. Letrozole successfully induced PCOS in the animals, evidenced by elevated levels of Sex Hormone Binding Globulin (SHBG), Follicle Stimulating Hormone (FSH), and progesterone, as well as the presence of multiple ovarian cysts. Hierarchical Cluster Analysis indicated that LDS was superior to metformin and the combination therapy in ameliorating PCOS symptoms. The findings suggest that there is little to no benefit in adding metformin to LDS for the clinical management of PCOS. Although these results are from preclinical studies, further case-controlled, randomized placebo studies on a larger patient sample are necessary to confirm these findings in clinical settings.

Differential regulation of GABAA receptor-mediated hyperexcitability at different stages of brain development in focal cortical dysplasia (FCD)

Focal cortical dysplasia (FCD) is a developmental abnormality of cortex commonly linked with drug-resistant seizures. Altered GABAergic activity is a key contributor to interictal discharges in FCD. In FCD, GABAA receptor associated epileptogenicity is dependent upon the age at seizure onset, as differential epileptogenic networks are observed in early and late onset FCD patients. But the contribution of GABAA receptor alteration to epileptogenic networks during development is unclear. We hypothesize that GABAergic signaling in FCD undergoes age-dependent molecular alterations, contributing to the development of distinct epileptogenic networks. In this study, we investigated age-dependent changes in GABA neurotransmitter levels, GABAA receptor α subunit expression, and GABAA receptor-mediated synaptic activity using the BCNU-rat model of FCD. GABA levels, mRNA, and protein expression of GABAA receptor α subunits were determined by HPLC, qPCR and western blot and spontaneous GABAergic activity from pyramidal neurons was recorded using whole cell patch-clamp technique. At postnatal days (P) 12 and 21, reduced expression of α1, 2 and 4 subunits were observed in FCD rats compared to control. Consistent with this, decreased amplitude and frequency of GABAergic events were observed in FCD rats. In contrast, at P30 and P65, decreased GABA levels, without changes in receptor expression, were observed in FCD rats. Consistently, reduction in the frequency of GABAergic events was observed in FCD rats compared to the control. Furthermore, treatment with tetrodotoxin (TTX) revealed that the observed alterations in GABAergic activity were predominantly action potential (AP)-dependent. Our findings indicate that distinct epileptogenic networks exist in FCD during early and late developmental stages. These networks are driven primarily by altered GABAergic activity, with early age changes linked to aberrant GABAA receptor configurations and late age changes associated with abnormal GABA levels.

Estrogen receptor alpha (ERα) partially modulates ketamine's sustained anxiolytic effects without altering its antidepressant properties in female rats

Ketamine is a rapid-acting antidepressant with sexually dimorphic effects. Female animals exhibit a higher sensitivity to its antidepressant properties, which has been associated with their ovarian hormone levels. One factor contributing to this sex difference is the faster rate of ketamine metabolism observed in females, potentially regulated by estrogen receptor alpha (ERα) through modulation of enzymatic activity. In this study, we explored the role of ERα in mediating the therapeutic effects of ketamine in adult female Wistar rats. To inhibit ERα, we administered its antagonist, methyl-piperidino-pyrazole (MPP; 1 mg/kg, IP), 24 h and 1 h prior to a single antidepressant dose of ketamine (10 mg/kg, IP) or saline (vehicle). We tested the animals in the forced swim test (FST), open field test (OFT), elevated plus maze (EPM), and auditory fear conditioning. Ketamine administration ameliorated behavioral despair observed in the vehicle group, and ERα antagonism did not affect this outcome. An interaction between MPP and ketamine was observed in anxiety-like behaviors assessed in the OFT and EPM; however, this effect did not reach significance in post-hoc analyses. Neither MPP nor ketamine affected fear memory, as measured in cued fear conditioning. These findings suggest that the sexually dimorphic antidepressant effects of ketamine occur independently of ERα activity, although ERα may influence neural circuits related to anxiety.

Murine modeling of menstruation identifies immune correlates of protection during Chlamydia muridarum challenge

The menstrual cycle influences the risk of acquiring sexually transmitted infections (STIs), including those caused by the pathogen Chlamydia trachomatis (C. trachomatis). However, the underlying immune contributions are poorly defined. A mouse model simulating the repetitive immune-mediated process of menstruation could provide valuable insights into tissue-specific determinants of protection against chlamydial infection within the cervicovaginal and uterine mucosae of the female reproductive tract (FRT). Here, we used the pseudopregnancy approach for inducing menstruation in naïve C57Bl/6 mice and performed vaginal challenge with Chlamydia muridarum (C. muridarum) over the course of decidualization, endometrial tissue remodeling, and menstruation. This strategy identified that a time point over pseudopregnancy corresponding to the late luteal phase of the menstrual cycle correlated with reduced bacterial burden. By evaluating the early infection site following challenge at this time point, we found that a greater abundance of NK cell populations and proinflammatory signaling, including IFNγ, were strongly correlated with protection. FRT immune profiling in uninfected mice over pseudopregnancy or in pig-tailed macaques over the menstrual cycle identified periodic NK cell infiltration into the cervicovaginal tissues and luminal surface occurring over a similar time frame. Notably, these cell populations were transcriptionally distinct and enriched for programs associated with NK cell effector functions. Depletion of FRT NK cells during the late luteal phase resulted in a loss of protection, enabling productive infection following C. muridarum challenge. This study shows that the pseudopregnancy murine menstruation model recapitulates dynamic changes occurring in mucosal immune states throughout the FRT as a result of endometrial remodeling and identifies NK cell localization at the FRT barrier site of pathogen exposure as essential for immune protection against primary C. muridarum infection.

Oestrous cycle synchronization protocols in rats using cloprostenol and progesterone injections

This study investigated the effectiveness of combining cloprostenol (Cl) and progesterone (Pg) injections for oestrous synchronization in female rats. A comprehensive series of experiments was conducted to explore the impact of hormonal injections on subsequent reproductive behaviour. The study involved dividing rats into distinct groups, with each group subjected to specific injections of either Cl, Pg, or their combinations. We observed a 100% conception efficiency within the first day after the last Cl injection in the Cl + Pg + Cl group. This finding underscores the remarkable effectiveness of the employed protocol, resulting in a rapid initiation of pregnancy in a substantial number of female rats on the same day.

Cassia siamea-Derived Silver Nanoparticles: Synthesis and Their Impact on Male Fertility Through Biochemical and Histopathologixcal Insights in Rats

The present study was designed to assess the effects of Cassia siamea leaf extract-mediated silver nanoparticles treatment on the fertility potential of male albino Wistar rats, to check their contraceptive efficacy. This plant is being traditionally used for various therapeutic purposes, including treating fever, skin diseases, hypertension, insomnia, diabetes, and asthma, as well as other pharmacological activities such as antimicrobial, antifertility, antioxidant, and analgesic properties. For this purpose, nanoparticles of the plant leaves were synthesized and characterized by different techniques as UV-Vis spectroscopic analysis, EDS, and DLS analysis. The animals were divided equally into five treatment groups, drug of 10, 20, and 30 mg/kg body weight per day was administered orally for 60 days, including group-I as control (vehicle treated) and group-V was kept at 30-day recovery period. A significant change in the reproductive organ weights, such as testes, epididymides, ventral prostate, seminal vesicles, and vas deferens, was observed at different dose levels compared to the control. Changes in sperm dynamics (motility and density) were also observed in the treated groups. Tissue biochemistry results revealed a substantial dose-dependent decrease in various parameters including protein, glycogen, cholesterol, fructose, and sialic acid in different reproductive organs, which might be silver-induced toxicity, whereas recovery groups showed a resurgence of these parameters once the doses were ceased for the following 30 days. In hormone analysis, a decrease in testosterone levels was also observed in a dose-response manner. Testosterone exhibited a correlation with the histopathological examination of the testis, revealing degenerative changes in seminiferous tubules and decreased spermatogenesis. These results support the notion that C. siamea leaf extract AgNPs possess antifertility potential and may be employed as a contraceptive.

The influence of ovarian activity and menopause on mental health: Evidence from animal models and women

Hormonal variations occurring throughout the female reproductive cycle have a significant impact on physical and mental health, particularly due to the influence of estradiol (E2) and progesterone (P4). These changes are directly related to alterations in neurological systems, being associated with conditions such as premenstrual syndrome (PMS), premenstrual dysphoric disorder (PMDD), and mood disorders during hormonal transition phases, such as perimenopause and menopause. Studies conducted in humans and animal models indicate that these fluctuations affect neurotransmitters, neural plasticity, and patterns of brain activity, ultimately influencing quality of life and mental health. Despite extensive research on the topic, the interactions between sex hormones, mental health, and reproductive aging still require further investigation, emphasizing approaches that simultaneously address experimental and behavioral aspects. Thus, this review aims to sumarize findings about the influence of hormonal fluctuations throughout the female reproductive lifespan, including transitions such as perimenopause and menopause, on mental health. A comparative analysis of data from studies in animal models and humans was conducted, highlighting neuroendocrine, behavioral, and emotional mechanisms associated with hormonal changes and their impacts on female mental health.

Prenatally androgenized PCOS mice have ovary-independent uterine dysfunction and placental inflammation aggravated by high-fat diet

Polycystic ovary syndrome (PCOS) is a common hyperandrogenic and metabolic condition in women. The syndrome is linked to subfertility and pregnancy complications, yet the independent effects of exposure to hyperandrogenism and obesity on endometrial function remain unclear. Here, PCOS-like mice were generated using prenatal androgenization (PNA) with dihydrotestosterone, followed by a prepubertal high-fat (HF) or standard diet. In ovariectomized mice, PNA impaired uterine closure during the implantation window, disrupted decidualization, and altered extracellular matrix- and inflammation-related gene expression. The effects were aggravated by the HF diet. In naturally mated, ovary-intact mice, PNA and HF diet affected decidual and placental gene expression, suggestive of placental dysfunction and inflammation, and induced fetal growth restriction. This study underlines the role of the uterus in adverse pregnancy outcomes in PCOS and identifies possible underlying mechanisms for future studies. Prepregnancy interventions targeting metabolic health and hyperandrogenism should be the next steps to optimize PCOS pregnancy outcomes.

Impact of relative estradiol changes during ovarian stimulation on blastocyst formation and live birth in assisted reproductive technology

This study aimed to evaluate the predictive value of relative change in E2 levels during controlled ovarian stimulation (COS) on embryo development and pregnancy outcomes in assisted reproductive technology (ART). We retrospectively analyzed 9,376 patients who underwent their first fresh ART cycle from January 1, 2020, to December 31, 2022. Patients were classified into four groups based on relative change in E2 levels: low response group, moderate response group, moderate-high response group, and high response group. The primary outcomes were blastocyst formation rate, clinical pregnancy rate, and live birth rate, while secondary outcomes included miscarriage rate and ectopic pregnancy rate. Most cycles (96.5%) demonstrated an increase in E2 levels during COS. The blastocyst formation rate significantly increased across the groups (low response group: 0.13, moderate response group: 0.21, moderate-high response group: 0.28, high response group: 0.34; P < 0.001). Multivariable logistic regression showed significantly higher blastocyst formation rates in the moderate response group (adjusted OR = 2.012, 95% CI: 1.687-2.399), moderate-high response group (adjusted OR = 4.613, 95% CI: 3.853-5.523), and high response group (adjusted OR = 11.295, 95% CI: 9.192-13.880) compared to the low response group. Both clinical pregnancy rate and live birth rate were significantly higher in the moderate-high response group and high response group compared to the low response group (clinical pregnancy rate: 54.5% and 61.5% vs. 35.5%, adjusted RR = 1.21 [95% CI: 1.03-1.42] and 1.27 [95% CI: 1.08-1.51]; live birth rate: 44.9% and 52.0% vs. 25.7%, adjusted RR = 1.27 [95% CI: 1.06-1.52] and 1.35 [95% CI: 1.11-1.64]). However, no significant differences were observed in either clinical pregnancy rate or live birth rate between the moderate response group and low response group (clinical pregnancy rate: adjusted RR = 1.07 [95% CI: 0.91-1.25]; live birth rate: adjusted RR = 1.11 [95% CI: 0.92-1.33]). No significant differences in miscarriage rate or ectopic pregnancy rate were observed across the groups. Higher E2 responses were associated with improved embryo development and better pregnancy outcomes.

Advancing age and sex modulate antidyskinetic efficacy of striatal CaV1.3 gene therapy in a rat model of Parkinson's disease

We previously demonstrated that viral vector-mediated striatal CaV1.3 calcium channel downregulation in young adult (3mo) male parkinsonian rats provides uniform, robust protection against levodopa-induced dyskinesias (LID). Acknowledging the association of PD with aging and incidence in male and female sexes, we have expanded our studies to include rats of advancing age of both sexes. The current study directly contrasts age and sex, determining their impact on efficacy of intrastriatal AAV-CaV1.3-shRNA to prevent LID induction, removing the variable of levodopa-priming. Considering both sexes together, late-middle-aged ('aged'; 15mo) parkinsonian rats receiving AAV-CaV1.3-shRNA developed significantly less severe LID compared control AAV-scramble(SCR)-shRNA rats, however therapeutic benefit was significantly less robust than observed in young males. When considered separately, females showed significantly less therapeutic benefit than males. Furthermore, aged non-cycling/proestrous-negative female rats were refractory to LID induction, regardless of vector. This study provides novel insight into the impact of age and sex on the variable antidyskinetic responses of CaV1.3-targeted gene therapy, highlighting the importance of including clinically relevant age and sex populations in PD studies.

Sexual Dimorphism in Levodopa-Induced Dyskinesia Following Parkinson's Disease: Uncharted Territory

Sexual dimorphism is well-documented in Parkinson's disease (PD); however, when it comes to levodopa-induced dyskinesia (LID), epidemiological and clinical findings are scarce. This is an oversight because recent studies show significant correlations between LID risk and female sex. Estrogen strongly impacts neuronal function, affecting cognitive tasks such as movement, object recognition, and reward. In movement pathways, estrogen increases dopamine synthesis, transmission, and regulation, resulting in neuroprotection for PD in women. However, following menopause, PD prevalence, symptom severity, and LID risk increase for women. Consequently, early to mid-life estrogen state is neuroprotective, but later in life becomes a risk factor for PD and LID. This review explores estrogen's action in the brain, specifically within the dopamine system. Sexual dimorphism is described for the prevalence and onset of PD and LID. We examine the cellular basis of estrogen's role in sexual dimorphism and integrate these ideas to hypothesize why the risk for LID is higher for women, than men, with PD. Lastly, this review proposes that women with PD need their symptoms to be considered and managed differently to males. Treatment of women with PD should be based on their menopausal stage, as estrogen may be masking, exacerbating, or complicating symptoms. Importantly, we present these concepts to stimulate discussion among clinical and bench scientists so that key experiments can be conducted to examine the mechanisms underlying LID, so they can be prevented to improve the quality of life for women and men living with PD in the future.

Cumulative effect of stress on decisional exploration-to-exploitation switch assessed through a gambling task in female mice

Survival and well-being hinge on an organism's ability to evaluate options, weighing costs and benefits to make adaptive decisions. It has long been shown that stress influences cognition and reward-related behaviour, the nature of which depends on the stressor's type and duration as well as gene x environment interactions. However, how stress influence decision-making in females has not been completely elucidated. Here, we have developed a new mouse gambling task (mGT) adapted to assess decision-making under uncertainty and risk. Adult female C57BL/6JRj mice administered with corticosterone (CORT) for 5 or 8 weeks reached similar final performance in the mGT as vehicle-treated controls. All groups tended to learn to maximize gain as the task progressed. Our results revealed that individual choice kinetics is impacted by chronic exposure to CORT, showing an accentuated sensitivity to penalties in female mice. These results confirm the suitability of our new mGT to assess decision-making under uncertainty and risk and are in line with previous reports of the effect of chronic CORT treatment on decision-making in male mice. Thereby this study provides new insights into the influence of sex and stress on decision-making.

Hormonal contraceptives during adolescence impact the female brain and behavior in a rat model

Millions of people take hormonal contraceptives (HCs), often starting during adolescence when ovarian hormones influence brain and behavioral maturation. However, there is a fundamental lack of information about the neurobehavioral consequences of hormonal alterations via adolescent HC use. To begin addressing this gap, we validated a rodent model of adolescent HC administration and characterized its impact on endocrine, transcriptional, and behavioral endpoints. Cohorts of intact post-pubertal female Sprague-Dawley rats received daily subcutaneous injections of either vehicle or HC [10 μg ethinyl estradiol (EE) + 20 μg levonorgestrel (LNG)] for the duration of adolescence from postnatal day (PND) 35 to PND56. Blood and brain tissue was collected at PND57. Other cohorts received daily injections of vehicle or HC from PND35 until behavioral assays were completed on PND57-64. HC treatment was effective, as vaginal lavage indicated disrupted estrous cycling and ELISA indicated suppressed serum luteinizing hormone in HC-treated rats. Liquid chromatography-mass spectrometry analysis showed EE and LNG in serum and brain as well as diminished serum and brain levels of allopregnanolone and testosterone in HC-treated rats. NanoString nCounter analysis indicated that adolescent HC administration impacted expression of genes related to synapses, white matter, neuroimmune, monoamine, and hormone signaling in the hypothalamus and medial prefrontal cortex. While no effects of HCs were seen on sociability in the social preference test or stress coping behavior in the forced swim test, adolescent HC administration diminished risk-assessment behaviors in the novelty-induced hypophagia paradigm and altered anxiety-like behavior in the open field test and elevated plus maze. Overall, these data suggest that exposure to contraceptive hormones during the critical developmental period of adolescence may shape the brain and behavior.

Whole-transcriptome sequencing reveals the effects of acupuncture on early embryos post-IVF-ET in poor ovarian response

BACKGROUND

Poor ovarian response (POR) refers to a pathological condition where the ovaries respond inadequately to gonadotropin stimulation during ovulation induction. The decline in both the quantity and quality of available oocytes makes achieving pregnancy through IVF-ET more challenging. Several studies have demonstrated that acupuncture can improve embryo quality, increase the number of high-quality embryos, and enhance pregnancy outcomes in IVF-ET patients, although the underlying mechanisms remain unclear. Therefore, this study aimed to investigate the molecular mechanisms by which acupuncture influences early embryo development in POR mice after IVF-ET through whole-transcriptome sequencing.

METHODS

We established POR mice model and performed acupuncture treatment. Fresh denuded oocytes were retrieved and transplanted via IVF-ET into new donor female mice to obtain early-stage embryo tissues. Vaginal smear tests were conducted to monitor estrous cycle changes, while oocyte retrieval, ovarian wet weight, and ovarian index were assessed. Serum concentrations of anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), estradiol (E2), and luteinizing hormone (LH) were measured via ELISA. Histopathological changes and apoptosis in the ovaries were evaluated using HE and TUNEL staining. Whole-transcriptome sequencing was employed to establish expression profiles of differentially expressed mRNAs (DEmRNAs), DEmiRNAs, DElncRNAs, and DEcircRNAs. The circ/lncRNA-miRNA-mRNA network was constructed to analyze the biological functions and potential mechanisms of acupuncture on early embryo development post-IVF-ET in POR mice.

RESULTS

Our results demonstrated that acupuncture improved ovarian function in POR mice, corrected serum hormone imbalances, and alleviated abnormal apoptosis in ovarian granulosa cells. Through whole-transcriptome sequencing, we identified 685 DEmRNAs, 13 DEmiRNAs, 325 DElncRNAs, and 4 DEcircRNAs exhibiting regulatory trends. By constructing the circ/lncRNA-miRNA-mRNA network, we found that miR-291a-3p, miR-294-3p, and miR-295-3p may serve as key targets influencing early embryo development via multiple pathways, including the Toll-like receptor signaling pathway and p53 signaling pathway.

CONCLUSION

Overall, our study is the first to reveal the molecular mechanisms by which acupuncture improves early embryo development under POR conditions, providing new evidence for the use of acupuncture in assisted reproduction.

Differential Effects of Canonical Androgens and 11-Ketotestosterone on Reproductive Phenotypes and Folliculogenesis in Mouse Model of PCOS

Background: Polycystic ovary syndrome (PCOS) is a common female endocrine disorder characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphology. While canonical androgens like testosterone (T) and dihydrotestosterone (DHT) are well studied in PCOS pathophysiology, the role of 11-ketotestosterone (11KT) remains unclear. This study investigates the differential effects of these androgens on folliculogenesis, ovulation, and steroidogenesis using in vivo and in vitro models. Methods: Four-week-old female C57BL/6 mice received T, DHT, or 11KT for six weeks. The assessments included body weight, estrous cyclicity, serum hormone profiles, ovarian histology, and follicle classification. In parallel, large preantral follicles were cultured with each androgen to evaluate follicle growth, antrum formation, and ovulation capacity. Androgen receptor (AR) signaling and steroidogenic function were analyzed using western blotting, RT-qPCR, and luciferase reporter assays. Results: The DHT-treated mice exhibited increased weight gain, whereas 11KT-treated mice showed reduced weight gain. T and DHT disrupted the estrous cycle, while 11KT prolonged diestrus. All androgen treatments led to ovarian morphological changes, including follicular arrest and cystic features. In vitro, all androgens enhanced follicle growth, but only T and DHT inhibited ovulation. The AR expression was elevated across all androgen-treated groups, but only DHT significantly activated AR and CYP19A1 promoters. Conclusions: 11KT induces a distinct and milder PCOS-like phenotype compared to classical androgens, promoting follicle growth with minimal impact on ovulation or steroidogenic disruption. These findings underscore the heterogeneity of PCOS and suggest that different androgen profiles may drive diverse clinical phenotypes. By elucidating the distinct roles of different androgens, this may lead to better stratification of PCOS phenotypes based on predominant androgen types for more precise diagnosis and individualized management.

CaMKIIα-NpHR-Mediated Optogenetic Inhibition of DRG Glutamatergic Neurons by Flexible Optic Fiber Alleviates Chronic Neuropathic Pain

Glutamatergic neurons of the dorsal root ganglion (DRGg) exert a significant effect on peripheral nociceptive signal transmission. However, assessing the explicit modulatory effect of DRGg during chronic neuropathic pain (CNP) with neuromodulation techniques remains largely unexplored. Therefore, we inhibited DRGg by optogenetic stimulation and examined whether it could alleviate CNP and associated anxiety-related behaviors in a chronic compressed DRG (CCD) rat model. The CCD pain model was established by inserting an L-shaped rod into the lumbar 5 (L5) intervertebral foramen, and either AAV2-CaMKIIα-eNpHR3.0-mCherry or AAV2-CaMKIIα-mCherry was injected into the L5 DRG. Flexible optic fibers were implanted to direct yellow light into the L5 DRG. Pain and anxiety-related behavioral responses were assessed using mechanical threshold, mechanical latency, thermal latency, and open field tests. In vivo single-unit extracellular recording from the DRG and ventral posterolateral (VPL) thalamus was performed. CNP and anxiety-related behavioral responses along with increased neural firing activity of the DRG and VPL thalamus were observed in CCD animals. Enhanced expression of nociception-influencing molecules was found in the DRG and spinal dorsal horn (SDH). In contrast during optogenetic stimulation, specific DRGg inhibition markedly alleviated the CNP responses and reduced the DRG and VPL thalamic neural hyperactivity in CCD animals. Inhibition of DRGg also reduced the active expression of nociceptive signal mediators in the DRG and SDH. Taken together, our findings suggest that CaMKIIα-NpHR-mediated optogenetic inhibition of DRGg can produce antinociceptive effects in CCD rats during peripheral nerve injury-induced CNP condition by altering peripheral nociceptive signal input in the spinothalamic tract.

Effects of 700 MHz radiofrequency radiation (5 G lower band) on the reproductive parameters of female Wistar rats

The advent of 5 G technology has raised concerns about its potential biological effects, particularly reproductive health being one key area of focus. This study investigated the impact of 700 MHz, a lower 5 G frequency band, on the reproductive health of female Wistar rats. The experiment analyzed the effects of short-term and long-term exposure to 700 MHz mobile radiation on female Wistar rats. Rats were divided into three groups (control, sham-exposed, and exposed), with sample sizes of n = 6 for short-term and n = 8 for long-term exposure. For short-term exposure, rats were subjected to 6 hrs of radiation daily for 10 days, while for long-term exposure, rats exposed 4 hrs daily for 60 days. Physiological parameters, including estrous cyclicity, were monitored, and histopathological and biochemical analyses were conducted on harvested ovaries. Comet assay was performed to assess DNA damage. The results indicated no changes in estrous cycles or comet assay parameters in either exposure group. Serological hormone levels, including estradiol and progesterone, remained within normal ranges, but a slight yet significant increase in testosterone levels was observed in exposed groups. Oxidative stress markers revealed elevated malondialdehyde (MDA) levels and significant decreases in superoxide dismutase (SOD), total sulfhydryl content, and ferric reducing antioxidant power (FRAP) in exposed ovaries. Histopathological analysis showed no significant changes in ovarian morphology in short-term exposure but revealed alterations, including cystic follicles and abnormal vasculature, in long-term exposure. These findings suggest that 700 MHz radiation may induce oxidative stress and tissue changes in ovarian samples over prolonged exposure.

Diacerein and myo-inositol alleviate letrozole-induced PCOS via modulation of HMGB1, SIRT1, and NF-kB: A comparative study

Polycystic ovary syndrome (PCOS) is the most prevalent cause of anovulatory infertility in women. Myo-inositol supplementation has displayed effectiveness in curing PCOS patients. Diacerein, an anti-inflammatory medication, has not been extensively studied in the context of reproductive disorders. This study aimed to compare the role of myo-inositol and diacerein in PCOS and the probable mechanisms mediating their actions. Forty adult female rats were divided equally into the following: control, PCOS, PCOS+Myo-inositol, and PCOS+Diacerein groups. Rats were subjected to arterial blood pressure (ABP), electromyography (EMG), and uterine reactivity measurements. Blood samples were collected for measuring hormonal assays, glycemic state, lipid profile, oxidative stress, and inflammatory markers. Ovaries and uteri were extracted for histological examination, including hematoxylin and eosin staining, Masson's trichrome staining, immunohistochemistry, and rt-PCR analysis of ovarian tissues. PCOS was associated with significant increases in ABP, uterine frequency and amplitude of contraction, luteinizing hormone, testosterone, lipid, glycemic and inflammatory markers, malondialdehyde, high-mobility group box 1 (HMGB1), nuclear factor kappa (NF-kB), ovarian fibrosis, and endometrial thickening. In contrast, there was a significant reduction in follicular stimulating hormone, reduced glutathione, and Sirtuin 1 (SIRT1) when compared with control group. Both myo-inositol and diacerein counteract PCOS changes; but diacerein's effects were superior to myo-inositol's for all parameters, except for lipid and glycemic markers. Diacerein possessed anti-inflammatory properties and showed significant efficacy in mitigating the endocrinal, metabolic, and ovarian structural alterations linked to PCOS. Its beneficial actions likely stem from reducing oxidative stress, dyslipidemia, and hyperglycemia, potentially through the modulation of HMGB1, SIRT1, and NF-kB pathways.

Leveraging research into sex differences and steroid hormones to improve brain health

Sex differences, driven in part by steroid hormones, shape the structure and function of the brain throughout the lifespan and manifest across brain health and disease. The influence of steroid hormones on neuroplasticity, particularly in the adult hippocampus, differs between the sexes, which has important implications for disorders and diseases that compromise hippocampus integrity, such as depression and Alzheimer disease. This Review outlines the intricate relationship between steroid hormones and hippocampal neuroplasticity across the adult lifespan and explores how the unique physiology of male and female individuals can affect health and disease. Despite calls to include sex and gender in research, only 5% of neuroscience studies published in 2019 directly investigated the influence of sex. Drawing on insights from depression, Alzheimer disease and relevant hippocampal plasticity, this Review underscores the importance of considering sex and steroid hormones to achieve a comprehensive understanding of disease susceptibility and mechanisms. Such consideration will enable the discovery of personalized treatments, ultimately leading to improved health outcomes for all.

Suoquan Wan mitigates bladder overactivity via modulation of neuroimmune homeostasis in perimenopausal rats

BACKGROUND

Overactive bladder (OAB) is a common disorder in perimenopausal women, involving detrusor regulation by bladder neuro-immune interactions. While Suoquan Wan (SQW) has shown efficacy in alleviating OAB symptoms, its underlying mechanisms remain unclear.

PURPOSE

The aim of this study was to investigate the therapeutic effects of SQW on perimenopausal overactive bladder (OAB) and elucidate its underlying mechanisms in restoring bladder neuro-immune homeostasis.

METHODS

Initially, vaginal smears were performed to identify perimenopausal rats. The effects of SQW on the structure and function of the perimenopausal bladder were assessed using urodynamic studies, organ bath assays, and histological analyses, including hematoxylin and eosin (HE) and Masson staining. Subsequently, single-nucleus RNA sequencing (snRNA-seq) was conducted to investigate the mechanisms by which SQW modulates neuron-macrophage interactions. To validate the sequencing data, PCR and immunofluorescence (IF) assays were utilized to evaluate neural homeostasis. Further analyses involved IF, flow cytometry, and fluorescence bead assays to determine the function and proportion of bladder macrophages. The co-localization of neurons and macrophages was visualized using IF. Finally, transwell co-culture experiments were carried out to explore the regulatory effects of SQW on bladder neuro-immune homeostasis.

RESULTS

SQW significantly attenuates the frequency of non-micturition contractions and reduces residual urine volume, alleviates detrusor hyperactivity in OAB rats in response to external stimuli such as EFS, CCh, and KCl, and markedly improves urinary efficiency in perimenopausal OAB rats. SnRNA-seq data indicate that SQW modulates bladder neuro-immune homeostasis in these rats. Furthermore, SQW obviously decreases the proportion of ChAT-positive nerve fibers while enhancing the abundance of nNOS and MAP-positive nerve fibers in the bladder. SQW also reduces the proportion of CD45+ CD11b/C+MHCⅡ+ macrophages in the bladder muscle layer. Transwell co-culture assays reveal that the effects of SQW on MAP-2 and ChAT are mediated through the neuron-macrophage interaction mechanism.

CONCLUSIONS

SQW alleviated perimenopausal OAB by specifically modulating the neuron-macrophage interaction and enhancing bladder neuro-immune homeostasis.

Evaluation of the Protective Effects of Alpha Lipoic Acid on Bleomycin-Induced Ovarian Toxicity

Chemotherapeutic drugs administered during cancer therapy, may lead to the depletion of ovarian follicles, and subsequent infertility in fertile patients. We aimed to determine toxic effects of bleomycin (BLM) on rat ovary, and to evaluate protective effects of alpha lipoic acid (ALA) on BLM toxicity. The total of 30 adult female rats were split into 4 groups. First, an intramuscular injection (i.m) of BLM (30 mg/m2) was administered to BLM and BLM + ALA groups except the control and ALA groups on the 1st, 8th and 15th days. The control group received 0.1 mL (i.m) saline on those days. BLM + ALA group received ALA (50 mg/kg) subcutaneously (s.c) for 2 weeks at the same time with BLM injections, and ALA group received ALA s.c for the same period. Ovarian tissues were evaluated by histopathological, stereological, immunohistochemical (StAR, VDAC2, Caspase-3, Bcl-2, and expression levels) and ELISA (AMH serum levels) methods. The vascular areas and collagen density increased in the medulla, and the volumes of medulla, cortex, and total ovary increased in BLM group, whereas these changes decreased in BLM + ALA group. On the other hand, VDAC2 and Caspase-3 expressions decreased, StAR and Bcl-2 expressions increased in BLM group, whereas VDAC2 and Caspase-3 expressions increased, and StAR and Bcl-2 expression levels significantly decreased in BLM + ALA group. Besides, follicle number and AMH levels decreased in the BLM group, but remarkably increased in the BLM + ALA group. We established that ALA may have ameliorative effects on the harmful effects of BLM on ovary.

Sex differences in long-term fear and anxiety-like responses to deep brain stimulation in a preclinical model of PTSD

Deep brain stimulation (DBS) is currently being investigated in patients and preclinical models of posttraumatic stress disorder (PTSD), but differences in behaviour according to sex remain elusive. We exposed female and male rats to fear conditioning and extinction. Thereafter, animals were treated with ventromedial prefrontal cortex DBS, followed by a battery of tests to measure fear and anxiety-like behaviour. As in our prior work, animals with high freezing scores during extinction (weak extinction; WE) were segregated from those with lower freezing scores (non-weak extinction; nWE), since the former population was previously shown to develop prolonged fear and anxiety-like responses. Vaginal lavages were collected after fear extinction to study the estrous cycle. After the experiments, brains were processed for the measurement of estrogen (ER) and progesterone receptors (PR) in the hypothalamus and hippocampus. We found that DBS-treated males had a more pronounced reduction in freezing than females during all recall sessions. In females, DBS induced an anxiolytic-like effect in the open field, while a reduction in the latency to feed during novelty suppressed feeding was noticed in both sexes. Noteworthy, a reduction in freezing during recall and anxiolytic-like responses following DBS were observed in males of all phenotypes, but only in nWE females. While no effect of the estrous cycle was noticed on fear memory, DBS-treated females in metestrus/diestrus during extinction had a more prominent response in the elevated plus maze. A similar expression of ERα, ERβ and PRβ in the hypothalamus and hippocampus was found in DBS-treated females and controls.

Seasonality of the estrus cycle in laboratory mice under constant conditions

Seasonality governs every aspect of life in the natural environment. Controlled laboratory settings are intended to keep animals under a constant set of environmental cues with no seasonality. However, prior research suggests that seasonal variation may exist despite aseasonal lab environments. Here, we examined whether the length of each phase of the estrus cycle varied seasonally in addition to seasonal changes in the overall estrus cycle length in a laboratory mouse strain (C57BL/6J) under standard laboratory housing conditions. We found that female C57BL/6J mice exhibited reproductive seasonality mirroring the outside environment, in a controlled "simulated summer" environment. In the winter and spring, females have longer ovulating phases (proestrus and estrus), compared to the fall. Females similarly experience lengthier quiescent phases (metestrus and diestrus) in the summer, compared to fall and winter. Interestingly, females showed no significant variation in overall estrus cycle length across seasons. Notably, females spent more time in ovulating phases across seasons than previously reported. Laboratory mice are sensitive to external seasonal changes, even when housed in standard laboratory environments designed to control light, temperature, and humidity. Humidity is indicated by some analyses as a potential seasonal cue, however, we cannot rule out other unidentified external cues that may provide information about external seasonal changes. These findings represent just one example of how seasonality may impact mouse physiology in laboratory settings, emphasizing the need to account for such influences in biomedical research and improve environmental control in mouse holding facilities.

Impact of PM2.5 Exposure from Wood Combustion on Reproductive Health: Implications for Fertility, Ovarian Function, and Fetal Development

This study evaluates the impact of PM2.5 exposure from wood combustion on reproductive health and fetal development using an experimental model in Sprague Dawley rats. The study was conducted in Temuco, Chile, where high levels of air pollution are primarily attributed to residential wood burning. A multigenerational exposure model was implemented using controlled exposure chambers with filtered (FA) and unfiltered (NFA) air. Second-generation (G2) female rats (n = 48) were exposed pregestationally (60 days) and gestationally (23 days) under four conditions: FA/FA, FA/NFA, NFA/FA, and NFA/NFA. PM2.5 concentration and composition were monitored using beta-ray attenuation and X-ray fluorescence spectrometry. Reproductive parameters, ovarian follicle counts, and hormonal levels were assessed via vaginal cytology, histological analysis, and chemiluminescence immunoassays. PM2.5 exposure disrupted estrous cyclicity (p = 0.0001), reduced antral and growing follicles (p = 0.0020; p = 0.0317), and increased post-implantation losses (p = 0.0149). Serum progesterone and estradiol levels were significantly altered (p < 0.05). Despite ovarian disruptions, fertility rates remained unchanged. These findings suggest that chronic exposure to wood smoke-derived PM2.5 adversely affects ovarian function and fetal growth without significantly impairing overall reproductive capacity. This study highlights the need for public health policies to mitigate wood smoke pollution.

A Leptin Receptor Mutation Which Impairs Fertility in Ewes Causes Delayed Puberty in Male and Female Mice

Reproductive function is tightly linked to nutritional status due to its high energetic demands. Leptin, a key adipose tissue-derived hormone signalling energy reserves to the brain, integrates metabolic status with the hypothalamic-pituitary-gonadal axis to ensure reproductive function is maintained or suppressed appropriately. Mutations in leptin or its receptor (LepR) are known to cause infertility and obesity in mice. In Davisdale ewes, 2 naturally occurring LepR mutations (R62C and P1019S) were associated with delayed puberty and subfertility, but their effects in males or in other species remain to be determined. This study examined the impact of analogous LepR mutations (A63C and P1018S) in mice using CRISPR-Cas9 gene editing. Puberty onset, adult fertility, and metabolic phenotypes were assessed in wild-type, heterozygous, and homozygous mutant mice. The A63C mutation, located in the extracellular domain of the receptor, resulted in increased body weight and adiposity in females, along with delays in puberty onset in both sexes. Despite these delays, adult reproductive function was maintained. Immunohistochemical analysis revealed no detectable reductions in leptin-induced pSTAT3, pERK1/2, or pmTOR signalling in the hypothalamic arcuate nucleus in either mutant line, indicating these pathways remain largely intact. These findings demonstrate the conserved importance of this region of the leptin receptor for puberty onset and adiposity across species, but also the resilience of leptin signalling in preserving reproductive function despite genetic variation.

Ovarian cryopreservation with rapamycin improves fertility restoration in a murine orthotopic transplantation model

Currently, the only fertility preservation option of prepubertal patients is ovarian tissue cryopreservation followed by autotransplantation (OTCTP). Once in remission and patients desire to conceive, autotransplantation of frozen/thawed tissue is performed. A major issue of this technique is follicular loss directly after transplantation, mainly due to follicle activation. Our previous research showed that adding rapamycin to the freezing medium counteracted follicle proliferation and activation induced by OTCTP in heterotopic autotransplantation of ovaries in mice. Our current study aimed to test the potential of this approach to improve fertility restoration in mice. Forty 4-week-old female C57BL/6 mice underwent unilateral oophorectomy followed by slow-freezing of ovaries with or without rapamycin. After chemically disabling the remaining ovary, orthotopic autotransplantation was performed. After recovery, estrous cycle analysis was conducted using daily vaginal smears. The mice were mated with males for 4 months, and pregnancy outcomes were recorded. After mating, half the females were super-ovulated for oocyte quantification and ovarian analysis, while the others had their ovaries collected for analysis of remaining primordial follicles using immunohistochemistry. Female mice whose ovaries were cryopreserved with rapamycin prior to chemically disabling the remaining ovary and orthotopic autotransplantation, gave birth to more pups (102 rapamycin, 48 control). The live birth rate was also higher (P = 0.0025) when ovaries were cryopreserved in rapamycin compared to control medium. Additionally, more mice in the rapamycin group gave birth (13 rapamycin, 8 control) with a higher average litter size (P = 0.0837). More mice had primordial follicles left at the end of the experiment in the rapamycin group (P = 0.0397). Superovulation showed a similar number of oocytes collected (P = 0.4462). While rapamycin did not influence cyst formation after autotransplantation, mice that developed ovarian cysts gave birth to fewer pups per dam (P = 0.0119) with a lower live birth rate compared to mice without ovarian cysts (P = 0.0032). The use of rapamycin improved fertility restoration in mice. Using rapamycin during OTCTP in humans could potentially resolve the massive follicular loss directly after grafting, and thus eventually lead to better opportunities for women to become pregnant.

The effect of norethisterone acetate on the uterine telocytes, immune cells and progesterone receptors in albino rats

This study is the first attempt to examine the effects of NETA on immune cells and telocytes. The results of this study form an important knowledge base for the development of new information on the mechanism of contraceptive action of NETA in the uterus. Norethisterone acetate (NETA) is a synthetic progestogen medication commonly utilized in birth control pills, menopausal hormone therapy, and for curing abnormal uterine bleeding and endometriosis. Furthermore NETA has many beneficial uses in veterinary medicine as control and synchronization of estrous cycle. The impact of NETA on the endometrial stromal cells (ESCs), telocytes, and uterine immune cells is not well understood. Therefore, this study focuses on assessing changes in uterine immune cells, ESCs, and telocytes following exposure to NETA in albino rats. To achieve this objective, fourteen adult female albino rats were randomly divided into two groups: a control group and an NETA-treated group. Rats in the control group received daily pelleted food, water, and were oral administered of 2 ml distilled water. In contrast, rats in the NETA-treated group received daily pelleted food, water, and were orally administered 20 µg of NETA dissolved in 2 ml distilled water. The experiment spanned three weeks. The findings of this study revealed that NETA usage increases the infiltration and activity of immune cells (eosinophils, neutrophils, macrophages, lymphocytes, and mast cells). Furthermore, it enhances the vesicular activity of uterine telocytes and their communication with various immune cells. NETA also influences decidualization and the immunoexpression of progesterone receptors in uterine epithelial and immune cells. This study concludes that the primary mechanism by which NETA controls pregnancy is through decidual (pregnancy-like) effects or improper decidualization, which inhibits fertilization and implantation respectively. Our research provides evidence of the contraceptive mechanism of NETA from an immunological perspective in an animal model.

Dopamine D1 receptor agonist alleviates post-weaning isolation-induced neuroinflammation and depression-like behaviors in female mice

BACKGROUND

Major depressive disorder is a significant global cause of disability, particularly among adolescents. The dopamine system and nearby neuroinflammation, crucial for regulating mood and processing rewards, are central to the frontostriatal circuit, which is linked to depression. This study aimed to investigate the effect of post-weaning isolation (PWI) on depression in adolescent mice, with a focus on exploring the involvement of microglia and dopamine D1 receptor (D1R) in the frontostriatal circuit due to their known links with mood disorders.

RESULTS

Adolescent mice underwent 8 weeks of PWI before evaluating their depression-like behaviors and the activation status of microglia in the frontostriatal regions. Selective D1-like dopamine receptor agonist SKF-81,297 was administered into the medial prefrontal cortex (mPFC) of PWI mice to assess its antidepressant and anti-microglial activation properties. The effects of SKF-81,297 on inflammatory signaling pathways were examined in BV2 microglial cells. After 8 weeks of PWI, female mice exhibited more severe depression-like behaviors than males, with greater microglial activation in the frontostriatal regions. Microglial activation in mPFC was the most prominent among the three frontostriatal regions examined, and it was positively correlated with the severity of depression-like behaviors. Female PWI mice exhibited increased expression of dopamine D2 receptors (D2R). SKF-81,297 treatment alleviated depression-like behaviors and local microglial activation induced by PWI; however, SKF-81,297 induced these alterations in naïve mice. In vitro, SKF-81,297 decreased pro-inflammatory cytokine release and phosphorylations of JNK and ERK induced by lipopolysaccharide, while in untreated BV2 cells, SKF-81,297 elicited inflammation.

CONCLUSIONS

This study highlights a sex-specific susceptibility to PWI-induced neuroinflammation and depression. While targeting the D1R shows potential in alleviating PWI-induced changes, further investigation is required to evaluate potential adverse effects under normal conditions.

Real-time behavioral monitoring of C57BL/6J mice during reproductive cycle

Introduction

The present study aims to identify differences in behavioral profiles in post-pubertal C57BL/6J males and female mice across distinct phases of the reproductive cycle in a home cage environment.

Methods

To reduce human bias, we used an automated behavioral analysis system HomeCageScan from CleverSys Inc. Mice were monitored continuously, and resulting data were summarized across 24-h, light, and dark cycles. Behavioral activities of each period were analyzed using hierarchical clustering, factor analysis, and principal component analysis.

Results

Females exhibited higher levels of physically demanding activities, including ambulatory and exploratory movements, particularly during estrus and metestrus, with estrus showing up to 30% more activity than males. In contrast, males consistently engaged in more sleep-related behaviors across all phases, with significantly higher engagement during the light cycle compared to females in proestrus and estrus (p < 0.0001); the extent of this sex difference was greater during proestrus and estrus than in metestrus and diestrus (p < 0.01). Notably, distinct patterns of sleep fragmentation were observed, with females experiencing greater disruptions during the light cycle, while males showed similar disruptions during the dark cycle. Feeding and resourcing behaviors were highest in males, showing up to 20% increase compared to cycling females, as well as significantly engaging in habituation-related behaviors such as feeding and digging. Interphase differences were observed within females, such as a significant increase of habituation-related activities during estrus compared to proestrus and diestrus (p < 0.05), while during the dark cycle, these activities peaked during the diestrus phase (p < 0.05). Female mice in the metestrus phase exhibited more sleep-related behaviors than those in proestrus.

Discussion

Our study has revealed prevalent behavioral differences due to sex, and inter-phase variations by employing a continuous monitoring approach designed to reduce bias. This methodology ensures a comprehensive understanding of natural behavioral patterns and strategies.

Restoration of ovarian endocrine function with encapsulated immune isolated human ovarian xenograft in ovariectomized mice

Anti-cancer treatments cause premature depletion of the non-renewable ovarian reserve of follicles, the source of key steroid hormones, leading to premature ovarian insufficiency (POI) in 50% of pediatric cancer survivors. Patients with POI, especially at the onset of pubertal development, experience significant endocrine complications, including delayed growth, elevated risks of obesity and diabetes, and accelerated cardiovascular, musculoskeletal and neurological disorders as adults. The only approved pharmacological treatment for POI is an off-label prescribed hormone replacement therapy, which does not replace physiologically functioning ovaries. To restore production of ovarian hormones and protect against immune-mediated injury, we developed a hydrogel-based capsule for implantation of donor ovarian tissue. We evaluated the restoration of ovarian endocrine function in ovariectomized immunodeficient (NOD scid gamma, NSG) mice implanted with encapsulated xenografts over 20 weeks through daily vaginal cytology, hormone measurements and histological analysis of explanted human xenografts. The encapsulated xenografts integrated into the murine hypothalamus-pituitary-gonad (HPG) axis responding to circulating murine gonadotropins and restoring ovarian endocrine function. As controls, we implanted non encapsulated human ovarian xenografts comparable in size. Without the need for exogeneous stimulation, the estrous cyclicity resumed in both groups of mice 12 weeks post implantation and all mice regularly cycled experiencing between 3 to 8 estrous cycles in 20 weeks. The levels of estradiol gradually increased reaching on average 50pg/mL 20 weeks post implantation. Morphological analysis of the encapsulated grafts revealed presence of large antral follicles, ∼3mm in diameter, consistent with regular cyclicity and measurable levels of circulating hormones. This work demonstrates that endocrine function of encapsulated human ovarian tissue was not affected by the encapsulation and integrated with the host physiology similarly to the non-encapsulated controls.

Sex and Region-Specific Differences in Microglial Morphology and Function Across Development

Microglia are exceptionally dynamic resident innate immune cells within the central nervous system, existing on a continuum of morphologies and functions throughout their lifespan. They play vital roles in response to injuries and infections, clearing cellular debris, and maintaining neural homeostasis throughout development. Emerging research suggests that microglia are strongly influenced by biological factors, including sex, developmental stage, and their local environment. This review synthesizes findings on sex differences in microglial morphology and function in key brain regions, including the frontal cortex, hippocampus, amygdala, hypothalamus, basal ganglia, and cerebellum, across the lifespan. Where available, we examine how gonadal hormones influence these microglial characteristics. Additionally, we highlight the limitations of relying solely on morphology to infer function and underscore the need for comprehensive, multimodal approaches to guide future research. Ultimately, this review aims to advance the dialogue on these spatiotemporally heterogeneous cells and their implications for sex differences in brain function and vulnerability to neurological and psychiatric disorders.

The Effect of the Menstrual Cycle on Energy Intake: A Systematic Review and Meta-analysis

CONTEXT

Energy intake may differ across the menstrual cycle, with some studies identifying greater energy intake in the luteal phase (LP) compared with the follicular phase (FP) and others finding no clear differences. To date, no study has systematically synthesized the available data to draw more definite conclusions while considering any methodological inconsistencies between studies.

OBJECTIVE

The aim was to conduct a systematic review/meta-analysis in an effort to determine if there are differences in energy intake between the FP and LP.

DATA SOURCES

A systematic search strategy was developed and the search was conducted in 5 databases for studies that investigated any changes in energy intake across menstrual phases.

DATA EXTRACTION

Using Covidence, studies were identified and included if they contained individuals between the ages of 18 and 45 years, maintained an average body mass index (BMI) of 18.5-25 kg/m2, had no history of disordered eating, and included energy intake and menstrual cycle measurements in the FP and LP.

DATA ANALYSIS

Effect sizes were calculated for each study and a random-effects model was used to pool the results of each study.

RESULTS

Fifteen datasets were included consisting of 330 female participants with a mean age of 26 ± 4 years and mean BMI of 22.4 ± 2.3 kg/m2. Overall, there was a statistically significant difference (standardized mean difference = 0.69; P = .039) with increased energy intake in the LP compared with the FP (crude 168 kcal⋅d-1 average difference between phases).

CONCLUSION

Energy intake was found to be greater in the LP compared with the FP, providing insight into the effect of the menstrual cycle on energy intake. However, there were repeated methodological inconsistencies and future work should strive to utilize best practices for both energy intake measurement and menstrual phase specification.

Sex difference in TRPM3 channel functioning in nociceptive and vascular systems: an emerging target for migraine therapy in females?

Transient Receptor Potential Melastatin 3 (TRPM3) channels are Ca2+ permeable ion channels that act as polymodal sensors of mechanical, thermal, and various chemical stimuli. TRPM3 channels are highly expressed in the trigeminovascular system, including trigeminal neurons and the vasculature. Their presence in dural afferents suggests that they are potential triggers of migraine pain, which is originating from the meningeal area. This area is densely innervated by autonomous and trigeminal nerves that contain the major migraine mediator calcitonin gene-related peptide (CGRP) in peptidergic nerve fibers. Co-expression of TRPM3 channels and CGRP receptors in meningeal nerves suggests a potential interplay between both signalling systems. Compared to other members of the TRP family, TRPM3 channels have a high sensitivity to sex hormones and to the endogenous neurosteroid pregnenolone sulfate (PregS). The predominantly female sex hormones estrogen and progesterone, of which the levels drop during menses, act as natural inhibitors of TRPM3 channels, while PregS is a known endogenous agonist of these channels. A decrease in sex hormone levels has also been suggested as trigger for attacks of menstrually-related migraine. Notably, there is a remarkable sex difference in TRPM3-mediated effects in trigeminal nociceptive signalling and the vasculature. In line with this, the relaxation of human isolated meningeal arteries induced by the activation of TRPM3 channels is greater in females. Additionally, the sex-dependent vasodilatory responses to CGRP in meningeal arteries seem to be influenced by age-related hormonal changes, which could contribute to sex differences in migraine pathology. Consistent with these observations, activation of TRPM3 channels triggers nociceptive sensory firing much more prominently in female than male mouse meninges, suggesting that pain processing in female patients with migraine may differ. Overall, the combined TRPM3-related neuronal and vascular mechanisms could provide a possible explanation for the higher prevalence and even the more severe quality of migraine attacks in females. This narrative review summarizes recent data on the sex-dependent roles of TRPM3 channels in migraine pathophysiology, the potential interplay between TRPM3 and CGRP signalling, and highlights the prospects for translational therapies targeting TRPM3 channels, which may be of particular relevance for women with migraine.

Exploring Isotretinoin's Unexpected Acceleration of wound Healing: A rat model study

BACKGROUND

There have been clinical observations indicating that wound healing could be affected in patients undergoing systemic isotretinoin treatment. However, the precise role of retinoids in wound healing is still unclear and controversial. It is generally assumed that systemic retinoids could be harmful to wound healing, but this requires further investigation.

METHODS

Sprague-Dawley rats were gavaged with 2 mg/Kg/day of Isotretinoin and divided into three groups: Control, Isotretinoin/1month and Isotretinoin/2month. Photographic documentation and histomorphometric investigation were performed. The mRNA expressions of IL-6, MCP-1, VEGF, ICAM1, L-Selectin, TGF-1β, IL-10, IL-1α, and IL-8 were examined by qRT-PCR.

RESULTS

There was no significant impact on the rate of wound closure in Isotretinoin/1month group. However, a two-month regimen accelerated the wound-healing process. RT-PCR results revealed increased expression of IL-6, IL-8, IL-1α, TGF-β1, IL-10 MCP-1, ICAM1, L-Selectin, and VEGF rats that were administered Isotretinoin. Histological observations showed an increased number of mast cells in the wound areas of rats treated with Isotretinoin.

CONCLUSION

Our research indicated that taking Isotretinoin did not slow down wound healing and may even help the growth phase. Additionally, we did not observe any keloid formation during our histopathological analysis, suggesting that it may not be necessary to postpone invasive surgical procedures for six months after Isotretinoin therapy.

Hormonal contraceptives in adolescence impact the neuroimmune environment of the medial prefrontal cortex and hippocampus in female rats

Adolescence is a period of protracted neurodevelopment, during which the prefrontal cortex (PFC) undergoes significant remodeling. Microglia are integral to neurodevelopment and are sensitive to gonadal hormones, which increase during adolescence. Microglia and gonadal hormones can interact to influence adolescent development of the PFC (or medial prefrontal cortex [mPFC] in rodents). In females, gonadal hormones can be perturbed by using hormonal contraceptives (HCs). We predicted that HC administration over adolescence could affect microglia, other immunocompetent cells, and the neuroimmune environment of the developing mPFC. We also assessed HC effects on neuroimmune measures in the hippocampus, as the hippocampus also matures throughout adolescence and is sensitive to ovarian hormones. Intact post-pubertal female Sprague-Dawley rats received daily subcutaneous injections of vehicle or 10 ug ethinyl estradiol + 20 ug levonorgestrel (HCs) throughout adolescence from postnatal day (PND) 35-56. On PND 57 or 58, brains were collected for immunohistochemistry and qPCR. In the mPFC, HC-treated rats showed less Iba1 (microglia) immunolabeling and fewer Iba1+ cells. HC treatment also altered microglia morphology and reduced the spacing between microglia in the mPFC. In the hippocampus, HC-treated rats had reduced Iba1 immunolabeling in the dorsal CA1 and reductions in microglial cell complexity in dorsal CA1, ventral CA1, and ventral CA3. There were no effects of HCs on GFAP (astrocyte) immunolabeling in the mPFC or on astrocytes in any hippocampal subregion analyzed, except an increase in astrocyte number in the dorsal dentate gyrus. mPFC expression of genes related to phagocytosis (Cd68, Trem2) and neuroimmune signaling (Cx3cr1, Cx3cl1) were reduced in rats treated with HCs, but no gene expression changes were seen in the hippocampus. These data provide the first evidence that HCs given during the critical developmental period of adolescence can affect microglia properties in limbic brain regions.

TSST-1 promotes colonization of Staphylococcus aureus within the vaginal tract by activation of CD8+ T cells

Toxic shock syndrome toxin-1 (TSST-1) is a superantigen produced by Staphylococcus aureus and is the determinant of menstrual toxic shock syndrome (mTSS); however, the impact of TSST-1 on the vaginal environment beyond mTSS is not understood. Herein, we assessed how TSST-1 affects vaginal colonization by S. aureus, host inflammatory responses, and changes in microbial communities within the murine vagina. We demonstrated that TSST-1 induced a CD8+ T-cell-dependent inflammatory response in 24 h that correlated with S. aureus persistence within the vaginal tract. This increase was due to superantigen-dependent T-cell activation that triggered a change in microbial composition within the vaginal tract. Altogether, this study demonstrates that within the vaginal tract, TSST-1 modulates the vaginal microbiota to favor the survival of S. aureus in the absence of mTSS.IMPORTANCEToxic shock syndrome toxin-1 (TSST-1) is a superantigen toxin produced from Staphylococcus aureus that causes the menstrual form of toxic shock syndrome. This research demonstrates that TSST-1 also has a wider function within the vaginal tract than previously expected. We show that TSST-1, by activating CD8+ T cells, induces an inflammatory environment that modifies the vaginal microbiota to favor colonization by S. aureus. These are important findings as S. aureus can colonize the human vaginal tract efficiently and subsequently trigger dysbiosis within the microbial communities leading to several adverse outcomes such as decreased fertility, increased risks for sexually transmitted diseases, and issues related to pregnancy and birth.

Acute Exposure to Ozone Affects Circulating Estradiol Levels and Gonadotropin Gene Expression in Female Mice

Ozone, a critical air pollutant, has been shown to lead to systemic inflammation that can alter bodily functions, including hormone secretion, fertility, and the hypothalamic-pituitary-gonadal (HPG) axis. This study aimed to quantify changes in hormone production and follicle development after acute exposure to ozone using an animal model to identify the potential mechanisms underlying the observed effects of air pollution exposures on fertility and hormone secretion. To accomplish this, regularly cycling 8-week-old female C57BL/6J mice were exposed to 2 ppm of ozone or filtered air (control) for 3 h on the day of proestrus. Blood, ovaries, brain tissues, and pituitary glands were collected at 4 h after exposure to evaluate hormone levels, ovarian follicle distribution, and gene expression. Ovaries were also harvested at 24 h post-exposure. We found that at 4 h after ozone exposure, mice had significantly higher (30%) circulating estradiol levels than mice exposed to filtered air. This effect was accompanied by a decrease in mRNA expression of gonadotropin genes (LH, FSH) and gonadotropin-releasing hormone in the pituitary gland. Analysis of ovarian tissue at 4 h and 24 h after exposure showed no significant changes in follicle composition or the expression of steroidogenesis genes. We conclude that acute ozone exposure affects sex hormone levels and disrupts the HPG axis. Future studies addressing chronic or long-term effects of air pollution exposure are needed to elucidate the mechanisms by which ambient ozone affects endocrine function.

Edible Bird's Nest (EBN) Ameliorates the Effects of Indomethacin (IMC)-Induced Embryo Implantation Dysfunction in Rats

IMC has been reported to influence embryo implantation negatively in animals including rats. While EBN has been known to have a potential protective effect against reproductive toxicity, there is limited study on the effect of EBN on IMC toxicity in reproduction. This study aimed to ascertain whether pretreatment with a natural substance, Edible Bird's Nest (EBN), will reduce IMC-induced toxicity in pregnant rats. Thirty Sprague-Dawley rats divided into five equal groups were treated with EBN and IMC as follows: G1 = Control, G2 = IMC (4.33 mg/kg), G3 = IMC + EBN (4.33 mg/kg + 60 mg/kg), G4 = IMC + EBN (4.33 mg/kg + 90 mg/kg), and G5 = IMC + EBN (4.33 mg/kg +120 mg/kg). EBN was administered once daily for 8 weeks while IMC was injected subcutaneously. On day 8 after mating, all rats were sacrificed for blood sampling and embryo implantation rate (EIR) assessment; the uterine tissues were also subjected to immunohistochemical and histological analyses. G5 recorded significantly higher EIR, fertility index, and expression of epidermal growth factor receptor (EGFR) in the uterine section, across stroma cells, the glandular epithelium, and the luminal epithelium compared to control and other groups. IMC-induced inflammatory alterations, endometrial atrophy, vacuolar degeneration, and atrophy were not detected in uterine tissue sections in G4 and G5, with the latter group demonstrating the highest EIR with protective effects on uterine tissues. Thus, EBN supplementation might be of great benefit in guarding the fertility of individuals who depend on IMC for the treatment of chronic inflammatory illness.

Transport functions of intestinal lymphatic vessels

Lymphatic vessels are crucial for fluid absorption and the transport of peripheral immune cells to lymph nodes. However, in the small intestine, the lymphatic fluid is rich in diet-derived lipids incorporated into chylomicrons and gut-specific immune cells. Thus, intestinal lymphatic vessels have evolved to handle these unique cargoes and are critical for systemic dietary lipid delivery and metabolism. This Review covers mechanisms of lipid absorption from epithelial cells to the lymphatics as well as unique features of the gut microenvironment that affect these functions. Moreover, we discuss details of the intestinal lymphatics in gut immune cell trafficking and insights into the role of inter-organ communication. Lastly, we highlight the particularities of fat absorption that can be harnessed for efficient lipid-soluble drug distribution for novel therapies, including the ability of chylomicron-associated drugs to bypass first-pass liver metabolism for systemic delivery. In all, this Review will help to promote an understanding of intestinal lymphatic-systemic interactions to guide future research directions.

Outcome devaluation as a method for identifying goal-directed behaviors in rats

Goal-directed behaviors allow animals to act to satisfy needs and desires. The outcome devaluation task is an effective method for identifying goal-directed behaviors and distinguishing these from other types of behavior. Rats can be trained to lever-press for one or multiple distinct food rewards. During testing, the previously earned food-or a control food for comparison-is devalued by allowing the animal to freely feed on it until they are sated before testing lever-press performance under extinction conditions (no rewards are delivered). Behavior that adapts to reflect the new value of the outcome is considered goal-directed, whereas behavior that continues as in previous training despite the change in outcome value, is not. As more research groups have used this task, variability in the procedures used has increased. Here, we provide a reliable procedure for conducting the outcome devaluation task with appropriate controls. We describe the most common variants of the task and control conditions and discuss troubleshooting measures such as outcome pre-exposure, habituation to pre-feeding chambers and attention to animals' hunger levels. The method outlined can be executed in ~2 weeks including training (~8 d) and testing (1-4 d) by researchers who are familiar with performing behavioral tasks in laboratory rodents, although longer training may be considered for those who are interested in observing habitual control of behavior. This protocol should facilitate the comparison of results from different studies and laboratories, while allowing flexibility in the application of the outcome devaluation task to different research questions.

Asprosin-induced alterations in female rat puberty and reproductive hormonal profiles

OBJECTIVE

To investigate the comprehensive effects of daily chronic asprosin administration on various pubertal and reproductive parameters in female rats. This study aims to elucidate the role of asprosin in regulating the onset of puberty and its influence on hormonal profiles and ovarian histology.

METHODS

Asprosin was administered intraperitoneally (i.p.) at a dose of 500 ng/kg daily for eight weeks. Hormonal assays and histological analyses were performed to evaluate the effects of asprosin on the onset of puberty and reproductive function.

RESULTS

Daily chronic administration of asprosin accelerated the onset of the first oestrus. Hormonal assays revealed significant elevations in serum levels of Follicle-Stimulating Hormone (FSH) and Oestradiol (E2), while Inhibin B levels decreased. Histological evaluations demonstrated an increased number of primary and secondary follicles in ovarian tissue, without affecting primordial follicle counts or reproductive organ weights.

CONCLUSIONS

Role of adipokines in regulating puberty and reproductive function has increasingly gained recognition. This study aimed to provide the first comprehensive examination of the effects of daily chronic asprosin administration on pubertal and reproductive parameters in female rats. Utilising hormonal assays and histological analyses, asprosin was administered intraperitoneally (i.p.) at a dose of 500 ng/kg, daily, for eight weeks. Our findings revealed that daily chronic administration of asprosin accelerated the onset of the first oestrus. Hormonal assays showed significant elevations in serum levels of Follicle-Stimulating Hormone (FSH) and Oestradiol (E2), while Inhibin B levels decreased. Histological evaluations demonstrated an increased number of primary and secondary follicles in ovarian tissue, without affecting primordial follicle counts or reproductive organ weights. These results provide new insights into asprosin's role in advancing the age of first oestrus and modulating hormonal profiles, thereby offering potential benefits to the female reproductive system.

Rodent estrous cycle pattern: Harmonizing the cycle evaluation and interpretation

The estrous cycle is a sensitive endpoint from an endocrine disruptor perspective and is included in rodent reproductive toxicity studies. In this paper, the methods for estrous cycle timing and different approaches followed by testing laboratories for evaluating the days of the estrous cycle were reviewed. No major differences are identified for counting 4-day estrous cycle. However, when extended episodes of estrus (E) stages occur, the cycle counting differs between testing laboratories potentially resulting in misinterpretation and inaccurate outcome. Appearance of extended episodes of two to three E in an estrous cycle need explanation. Therefore, the following are proposed, 1) follow OECD guidance document for normal 4/5 day cycles, 2) recommends an update of the OECD document as in the current one it is unclear for a 5-day cycle ending with Proestrus(P) followed by episode(s) of estrus(E), 3) two episodes of E after P in a 5-day cycle and three consecutive episodes of E should be considered abnormal, and 4) stages prior to first E of the first cycle or after last E (last P of a 5-day) of last cycle should not be assumed a complete cycle. Additionally, call for collaboration is made to harmonize the cycle counting approach.

GLP-1R/NPY2R regulate gene expression, ovarian and adrenal morphology in HFD mice

Glucagon-like peptide-1 receptor (GLP-1R) and neuropeptide Y receptors (NPYRs) are expressed in reproductive tissues contributing to the regulation of gonadal function. This exploratory study examines the potential impact of their modulation by assessing the effects of exendin-4 (Ex-4) and peptide YY (PYY) (3-36) on endocrine ovaries and adrenals in high-fat diet (HFD) mice. Ex-4 and PYY(3-36) reduced blood glucose and energy intake, with no effects on body weight. While HFD did not impact the estrous cycle, Ex-4 increased metestrus frequency and decreased diestrus frequency resulting in 0% mice experiencing repeated diestrus or becoming acyclic. Luteinizing hormone levels were significantly higher in the Ex-4 and PYY(3-36) groups compared to the normal diet and HFD controls. In the adrenals, reduced capsule and zona glomerulosa thickness caused by HFD was reversed after peptide treatments. Within the ovaries, HFD increased the number of atretic follicles, an effect that disappeared after Ex-4 and PYY(3-36) treatments. Ex-4 also increased the number of corpora lutea owing to the prolonged metestrus phase. Gene expression analysis within the adrenals revealed the upregulation of Insr and the downregulation of Prgtr in HFD mice, while Ex-4 downregulated the expression of Gipr. The ovarian gene expression of Gipr, Npy1r and Prgtr was downregulated by Ex-4 treatment, while PYY(3-36) significantly downregulated the Prgtr expression compared to HFD mice. These data indicate that manipulating GLP-1R and NPY2R leads to changes in the reproductive physiology of mice. In addition, the observed alterations in the morphology and gene expression in the adrenals and ovaries imply a direct impact of these peptides on female reproductive function.

Nicotinamide riboside supplementation ameliorates ovarian dysfunction in a PCOS mouse model

Polycystic ovary syndrome (PCOS) is the leading cause of anovulatory infertility among women of reproductive age, yet the range of effective treatment options remains limited. Our previous study revealed that reduced levels of nicotinamide adenine dinucleotide (NAD+) in ovarian granulosa cells (GCs) of women with PCOS resulted in the accumulation of reactive oxygen species (ROS) and mitochondrial dysfunction. However, it is still uncertain whether increasing NAD+ levels in the ovaries could improve ovarian function in PCOS. In this study, we demonstrated that supplementation with the NAD+ precursor nicotinamide riboside (NR) prevented the decrease in ovarian NAD+ levels, normalized estrous cycle irregularities, and enhanced ovulation potential in dehydroepiandrosterone (DHEA)-induced PCOS mice. Moreover, NR supplementation alleviated ovarian fibrosis and enhanced mitochondrial function in ovarian stromal cells of PCOS mice. Furthermore, NR supplementation improved oocyte quality in PCOS mice, as evidenced by reduced abnormal mitochondrial clustering, enhanced mitochondrial membrane potential, decreased ROS levels, reduced spindle abnormality rates, and increased early embryonic development potential in fertilized oocytes. These findings suggest that supplementing with NAD+ precursors could be a promising therapeutic strategy for addressing ovarian infertility associated with PCOS.

Hypothyroidism Alters Uterine Kisspeptin System and Activity Modulators in Cyclic Rats

Hypothyroidism causes ovarian dysfunction and infertility in women and animals and impairs the hypothalamic expression of kisspeptin (Kp). However, kisspeptin is also expressed in the genital system, and the lack of the Kp receptor (Kiss1r) in the uterus is linked to reduced implantation rates. This study investigated the impact of hypothyroidism on the uterine expression of Kp and Kiss1r in female rats throughout the estrous cycle and the associated changes in uterine activity modulators. Hypothyroidism was induced through daily administration of propylthiouracil (PTU) over a period of 14 days. Plasma levels of LH, E2, and P4, cyclicity, body and uterine weight, uterine histomorphometry, and the gene and/or protein expression of Kiss1, Kiss1r, estrogen receptor α (ERα), progesterone receptor (PR), and thyroid hormone receptor α (TRα) were assessed. Additionally, proliferative activity (CDC-47) and the gene expression of uterine receptivity mediators (SMO, WNT4, BMP2, HAND2, MUC1, and LIF) were evaluated. Hypothyroidism prolonged the diestrus and increased progesterone levels during this phase, while decreasing luteinizing hormone and estradiol on proestrus. In the uterus, hypothyroidism reduced Kp immunostaining on diestrus and KISS1R mRNA levels on proestrus. These changes were accompanied by reduced endometrial glands, reduced uterine proliferative activity, and reduced ERα gene and protein expression. Additionally, hypothyroidism led to reduced uterine gene expression of LIF, BMP2, WNT4, and HAND2. On the other hand, thyroid hypofunction increased uterine PR and TRα immunostaining, while it reduced PGR gene expression on diestrus. These findings demonstrate that hypothyroidism reduces the expression of Kiss1/Kiss1r system in the uterus, which is associated with disrupted uterine estrogen and progesterone signaling and reduced expression of uterine receptivity mediators across the rat estrous cycle.

Increased Oxidative and Nitrative Stress and Decreased Sex Steroid Relaxation in a Vitamin D-Deficient Hyperandrogenic Rodent Model-And a Validation of the Polycystic Ovary Syndrome Model

BACKGROUND/OBJECTIVES

Both hyperandrogenism (HA) and vitamin D deficiency (VDD) can separately lead to impaired vascular reactivity and ovulatory dysfunction in fertile females. The aim was to examine the early interactions of these states in a rat model of PCOS.

METHODS

Four-week-old adolescent female rats were divided into four groups: vitamin D (VD)-supplemented (n = 12); VD-supplemented and testosterone-treated (n = 12); VDD- (n = 11) and VDD-and-testosterone-treated (n = 11). Animals underwent transdermal testosterone treatment for 8 weeks. Target VD levels were achieved with oral VD supplementation and a VD-free diet. Estrous cycles were followed by vaginal smear, and quantitative histomorphometric measurements of the ovaries were also taken. In the 8th week, testosterone- and estrogen-induced relaxation of coronary arterioles was examined with pressure angiography. Estrogen receptor (ER) density and oxidative and nitrative stress parameters (Poly-(ADP-Ribose)-Polymerase and 3-nitrotyrosine) in the vessel wall were investigated with immunohistochemistry.

RESULTS

VDD caused impaired estrous cycles, and testosterone caused anovulatory cycles (the cycles were stopped at the diestrous phase). VDD combined with testosterone treatment resulted in reduced testosterone and estrogen vasorelaxation, lower ER density, and higher oxidative and nitrative stress in the vessel wall.

CONCLUSIONS

PCOS with vitamin D deficiency may be associated with increased oxidative-nitrative stress in coronary arterioles. This oxidative and nitrative stress, potentially caused by hyperandrogenism and/or vitamin D deficiency, could impair estrogen-induced relaxation of the coronary arterioles, possibly by decreasing NO bioavailability and disrupting the estrogen-induced relaxation pathway.

GnRH pulse generator activity in mouse models of polycystic ovary syndrome

One in ten women in their reproductive age suffer from polycystic ovary syndrome (PCOS) that, alongside subfertility and hyperandrogenism, typically presents with increased luteinizing hormone (LH) pulsatility. As such, it is suspected that the arcuate kisspeptin (ARNKISS) neurons that represent the GnRH pulse generator are dysfunctional in PCOS. We used here in vivo GCaMP fiber photometry and other approaches to examine the behavior of the GnRH pulse generator in two mouse models of PCOS. We began with the peripubertal androgen (PPA) mouse model of PCOS but found that it had a reduction in the frequency of ARNKISS neuron synchronization events (SEs) that drive LH pulses. Examining the prenatal androgen (PNA) model of PCOS, we observed highly variable patterns of pulse generator activity with no significant differences detected in ARNKISS neuron SEs, pulsatile LH secretion, or serum testosterone, estradiol, and progesterone concentrations. However, a machine learning approach identified that the ARNKISS neurons of acyclic PNA mice continued to exhibit cyclical patterns of activity similar to that of normal mice. The frequency of ARNKISS neuron SEs was significantly increased in algorithm-identified 'diestrous stage' PNA mice compared to controls. In addition, ARNKISS neurons exhibited reduced feedback suppression to progesterone in PNA mice and their gonadotrophs were also less sensitive to GnRH. These observations demonstrate the importance of understanding GnRH pulse generator activity in mouse models of PCOS. The existence of cyclical GnRH pulse generator activity in the acyclic PNA mouse indicates the presence of a complex phenotype with deficits at multiple levels of the hypothalamo-pituitary-gonadal axis.

Sex differences in olfactory behavior and neurophysiology in Long Evans rats

In many species, olfactory abilities in females are more acute than those in males. Studies in humans show that women have lower olfactory thresholds and are better able to discriminate and identify odors than men. In mice, odorants elicit faster activation from a larger number of olfactory bulb glomeruli in females than in males. Our study explores sex differences in olfaction in Long Evans rats from a behavioral and electrophysiological perspective. Local field potentials (LFPs) in the olfactory bulb (OB) represent the coordinated activity of bulbar neurons. Olfactory gamma (65-120 Hz) and beta (15-30 Hz) oscillations have been functionally linked to odor perception. Spontaneous and odor-evoked OB LFPs were recorded from awake rats at the same time for 12 days. Odors used included urine of both sexes and monomolecular odorants characterized previously for correlation of volatility with behavior and OB oscillations. Sampling duration in a habituation context, baseline gamma and beta power, and odor-elicited beta and gamma power were analyzed. We find that females sample odorants for a shorter duration than males (just over 1-s difference). Although baseline gamma and beta power do not show significant differences between the two sexes, odor-elicited gamma and beta power in females is significantly lower than in males. Neither sampling duration nor beta and gamma power in females varied systematically with day of estrus. We further verify that variance of these behavioral and physiological measures is not different across sexes, adding to growing evidence that researchers need not be concerned about often-claimed additional variance in female subjects.NEW & NOTEWORTHY Olfaction plays a large role in evolutionary processes. However, we know little about sex differences in olfactory bulb neurophysiology, and many scientists believe that females are more variable because of estrus. We show that female rats sniff odors for shorter durations than males and have lower power in neural oscillations related to cognition. Estrus was not related to variance in any measures. Finally, males and females show equal variance on these behavioral and physiological processes.

The oestrous cycle stage affects mammary tumour sensitivity to chemotherapy

The response of breast cancer to neoadjuvant chemotherapy (NAC) varies substantially, even when tumours belong to the same molecular or histological subtype1. Here we identify the oestrous cycle as an important contributor to this heterogeneity. In three mouse models of breast cancer, we show reduced responses to NAC when treatment is initiated during the dioestrus stage, when compared with initiation during the oestrus stage. Similar findings were observed in retrospective premenopausal cohorts of human patients. Mechanistically, the dioestrus stage exhibits systemic and localized changes, including (1) an increased number of cells undergoing epithelial-to-mesenchymal transition linked to chemoresistance2-4 and (2) decreased tumour vessel diameter, suggesting potential constraints to drug sensitivity and delivery. In addition, an elevated presence of macrophages, previously associated with chemoresistance induction5, characterizes the dioestrus phase. Whereas NAC disrupts the oestrous cycle, this elevated macrophage prevalence persists and depletion of macrophages mitigates the reduced therapy response observed when initiating treatment during dioestrus. Our data collectively demonstrate the oestrous cycle as a crucial infradian rhythm determining chemosensitivity, warranting future clinical studies to exploit optimal treatment initiation timing for enhanced chemotherapy outcomes.