Estrous Cycle In Female Rats Research Articles

Determination of the rat estrous cycle vased on EfficientNet.

In the field of biomedical research, rats are widely used as experimental animals due to their short gestation period and strong reproductive ability. Accurate monitoring of the estrous cycle is crucial for the success of experiments. Traditional methods are time-consuming and rely on the subjective judgment of professionals, which limits the efficiency and accuracy of experiments. This study proposes an EfficientNet model to automate the recognition of the estrous cycle of female rats using deep learning techniques. The model optimizes performance through systematic scaling of the network depth, width, and image resolution. A large dataset of physiological data from female rats was used for training and validation. The improved EfficientNet model effectively recognized different stages of the estrous cycle. The model demonstrated high-precision feature capture and significantly improved recognition accuracy compared to conventional methods. The proposed technique enhances experimental efficiency and reduces human error in recognizing the estrous cycle. This study highlights the potential of deep learning to optimize data processing and achieve high-precision recognition in biomedical research. Future work should focus on further validation with larger datasets and integration into experimental workflows.

The estrous cycle has no effect on incubation of methamphetamine craving and associated Fos expression in dorsomedial striatum and anterior intralaminar nucleus of thalamus

Relapse is a major challenge in treating drug addiction, and drug seeking progressively increases after abstinence, a phenomenon termed “incubation of drug craving”. Previous studies demonstrated both sex differences and an effect of estrous cycle in female rats in incubation of cocaine craving. In contrast, while incubation of methamphetamine craving is similar across sexes, whether estrous cycle plays a role in this incubation has yet to be fully addressed. Moreover, whether neural mechanisms underlying incubation of methamphetamine craving differ across estrous cycles is largely unknown. To address these gaps, we first compared methamphetamine self-administration, and methamphetamine seeking on both abstinence days 1 and 28 between male rats and female rats across the estrous cycle. Next, we examined neuronal activation associated with incubated methamphetamine seeking in dorsomedial striatum (DMS) and lateral portion of the anterior intralaminar nucleus of thalamus (AIT-L), two brain areas previously implicated in incubation of methamphetamine craving. We found no effect of sex or estrous cycle on methamphetamine self-administration and methamphetamine seeking on abstinence days 1 and 28. We also found no effect of sex or estrous cycle on the number of Fos-expressing cells in DMS or AIT-L following methamphetamine seeking test. Taken together, our results showed that methamphetamine self-administration and incubation of methamphetamine craving was not dependent on sex or estrous cycles under our experimental condition, and the role of DMS and AIT-L in incubation of methamphetamine craving may be similar across sexes and across estrous cycles in female rats.

Cycle-dependent sex differences in expression of membrane proteins involved in cerebrospinal fluid secretion at rat choroid plexus

BackgroundFemale sex is a known risk factor of brain disorders with raised intracranial pressure (ICP) and sex hormones have been suggested to alter cerebrospinal fluid (CSF) dynamics, thus impairing ICP regulation in CSF disorders such as idiopathic intracranial hypertension (IIH). The choroid plexus (CP) is the tissue producing CSF and it has been hypothesized that altered hormonal composition could affect the activity of transporters involved in CSF secretion, thus affecting ICP. Therefore, we aimed to investigate if expression of various transporters involved in CSF secretion at CP were different between males and females and between females in different estrous cycle states. Steroid levels in serum was also investigated.MethodsFemale and male rats were used to determine sex-differences in the genes encoding for the transporters Aqp1 and 4, NKCC1, NBCe2, NCBE; carbonic anhydrase enzymes II and III (CA), subunits of the Na+/K+-ATPase including Atp1a1, Atp1b1 and Fxyd1 at CP. The estrous cycle stage metestrus (MET) and estrous (ES) were determined before euthanasia. Serum and CP were collected and subjected to RT-qPCR analysis and western blots. Serum was used to measure steroid levels using liquid chromatography tandem mass spectrometry (LC–MS/MS).ResultsSignificant differences in gene expression and steroid levels between males and ES females were found, while no differences were found between male and MET females. During ES, expression of Aqp1 was lower (p < 0.01) and NKCC1 was higher in females compared to males. CAII was lower while CAIII was higher in ES females (p < 0.0001). Gene expression of Atp1a1 was lower in ES compared to male (p = 0.0008). Several of these choroidal genes were also significantly different in MET compared to females in ES. Differences in gene expression during the estrus cycle were correlated to serum level of steroid hormones. Protein expression of AQP1 (p = 0.008) and CAII (p = 0.035) was reduced in ES females compared to males.ConclusionsThis study demonstrates for the first time that expression at CP is sex-dependent and markedly affected by the estrous cycle in female rats. Further, expression was related to hormone levels in serum. This opens a completely new avenue for steroid regulation of the expression of CSF transporters and the close link to the understanding of CSF disorders such as IIH.

Progesterone-loaded solid lipid nanoparticles for use in the regulation of the estrous cycle in female rats

Progesterone-loaded solid lipid nanoparticles for use in the regulation of the estrous cycle in female rats

Effects of sex and estrous cycle on intravenous oxycodone self-administration and the reinstatement of oxycodone-seeking behavior in rats.

The increasing misuse of both prescription and illicit opioids has culminated in a national healthcare crisis in the United States. Oxycodone is among the most widely prescribed and misused opioid pain relievers and has been associated with a high risk for transition to compulsive opioid use. Here, we sought to examine potential sex differences and estrous cycle-dependent effects on the reinforcing efficacy of oxycodone, as well as on stress-induced or cue-induced oxycodone-seeking behavior, using intravenous (IV) oxycodone self-administration and reinstatement procedures. In experiment 1, adult male and female Long-Evans rats were trained to self-administer 0.03 mg/kg/inf oxycodone according to a fixed-ratio 1 schedule of reinforcement in daily 2-h sessions, and a dose-response function was subsequently determined (0.003-0.03 mg/kg/inf). In experiment 2, a separate group of adult male and female Long-Evans rats were trained to self-administer 0.03 mg/kg/inf oxycodone for 8 sessions, followed by 0.01 mg/kg/inf oxycodone for 10 sessions. Responding was then extinguished, followed by sequential footshock-induced and cue-induced reinstatement tests. In the dose-response experiment, oxycodone produced a typical inverted U-shape function with 0.01 mg/kg/inf representing the maximally effective dose in both sexes. No sex differences were detected in the reinforcing efficacy of oxycodone. In the second experiment, the reinforcing effects of 0.01-0.03 mg//kg/inf oxycodone were significantly attenuated in females during proestrus/estrus as compared to metestrus/diestrus phases of the estrous cycle. Neither males nor females displayed significant footshock-induced reinstatement of oxycodone seeking, but both sexes exhibited significant cue-induced reinstatement of oxycodone seeking at magnitudes that did not differ either by sex or by estrous cycle phase. These results confirm and extend previous work suggesting that sex does not robustly influence the primary reinforcing effects of oxycodone nor the reinstatement of oxycodone-seeking behavior. However, our findings reveal for the first time that the reinforcing efficacy of IV oxycodone varies across the estrous cycle in female rats.

Investigation of Penicillin-induced Epilepsy Model in Female Rats with Different estrous Cycles by ECoG Method

ABSTRACT Aim: Epilepsy is a chronic neurological disease characterized by recurrent seizures resulting from an imbalance in neuronal excitation. It is known that there is a tendency for seizures to cluster in both men and women at certain periods. This study aims to compare electrocorticogram (ECoG) recordings in an experimentally induced epilepsy model using penicillin, conducted at different estrous cycles of female rats. Subjects and Methods: Prior to commencing the epilepsy experiments, vaginal smears were collected from the animals every morning for 1 week, at the same time each day, for cytological examination. After confirming that the estrous cycles (proestrus, estrous stage, metestrus, and diestrus) of the animals were normal and healthy, the experiment was initiated. Additionally, H and E staining was performed on the ovaries of the rats sacrificed at the end of the experiment to validate the estrous cycle phases. A total of 32 adult female Wistar rats were divided into four groups (proestrus, estrus, metestrus, and diestrus), each consisting of eight rats. The penicillin-induced epilepsy model involved anesthetizing the rats with 1.25 mg/kg urethane intraperitoneally, followed by the injection of penicillin G (500 IU, 2.5 μL, i.c.) into the cortex region through a skull opening. ECoG recordings were conducted using PowerLab analysis for 180 min. Statistical analysis of the results was performed using the SPSS program version 22 (IBM Corp., Armonk, NY, USA). One-way analysis of variance (ANOVA) and independent samples t-test were employed for groups with normally distributed data, while the Kruskal–Wallis test and Mann–Whitney U-test were used for groups with nonnormally distributed data. Statistical significance was set at P &lt; 0.05. Results: Histological evaluation confirmed that vaginal smears and ovarian histopathology were consistent with each other, validating the data pertaining to the groups. In the ECoG recording results, the spike-wave frequency between 6 and 10 min was higher in the metestrus group compared to the proestrus (P = 0.004), estrus (P = 0.046), and diestrus (P = 0.025) groups. No significant differences were observed among the groups in terms of spike-wave amplitude and latency. Conclusion: Our study using a penicillin-induced epilepsy model in female Wistar rats demonstrated that the spike-wave frequency was highest during the metestrus phase. This finding provides valuable insights for future studies aiming to understand and mitigate the sensitivity observed during the metestrus phase, which is characterized by rapid progesterone withdrawal.

Reproductive outcomes of neonatal exposure to betamethasone in male and female rats.

Betamethasone (BM) is the drug of choice for antenatal corticosteroid therapy for women at risk of preterm delivery because it induces fetal lung maturation and enhances survival after birth. However, our group reported evidence of fetal programming and impaired reproductive development and function in rats exposed during the critical window of genital system development. Therefore, we aimed to investigate the effects of BM on the sexual development of rats in the period that corresponds to antenatal corticosteroid therapy in humans. Male and female rats were exposed subcutaneously to BM at 0.1μg/g of pups' body weight or to a NaCl 0.9% solution (control) on postnatal days 1-3. It was observed that neonatal exposure to BM decreased body weight and weight gain in male and female rats during treatment. The estrous cycle was deregulated and LH level was decreased in female rats. In male rats, the sperm concentration in the caput-corpus of the epididymis was decreased, whereas the sperm transit time and sperm concentration in the cauda of the epididymis were increased. Our results demonstrated that neonatal exposure to BM impaired body growth of male and female rats, deregulated the estrous cycle of female rats, and altered sperm quality of male rats. Therefore, BM exposure from postnatal days 1 to 3 corroborated results previously observed after prenatal exposure to this drug. Despite the recognized importance of human antenatal corticosteroid therapy, the findings of this study should encourage further studies in order to minimize possible adverse postnatal effects.

Expression of phoenixin-14 and nesfatin-1 in the hypothalamo–pituitary–gonadal axis in the phases of the estrous cycle

Phoenixin-14 (PNX-14) and nucleobindin 2 (NUCB2)/nesfatin-1 are regulatory neuropeptides expressed in the hypothalamus. These neuropeptides can be effective in hormonal regulation of the hypothalamo–pituitary–gonadal (HPG) axis and reproductive functions. In the present study, the distribution of PNX-14 and NUCB2/nesfatin-1 in the hypothalamus, pituitary, ovary, and uterus tissues during the phases of the estrous cycle in female rats was investigated. Eighteen Wistar Albino rats determined among animals showing regular estrous cycle by vaginal smear method were divided into three groups: proestrus (Group I), estrus (Group II) and diestrus (Group III). Serum gonadotropin-releasing hormone (GnRH), plasma PNX-14, and NUCB2/nesfatin-1 concentrations were the highest, moderate, and lowest in estrus, diestrus, and proestrus phases, respectively. PNX-14 immunoreactivity in the supraoptic and arcuate nuclei of the hypothalamus and NUCB2/nesfatin-1 immunoreactivity in the paraventricular nuclei were particularly evident in the estrus phase. These neuropeptide immunoreactivities were decreased in different cells of anterior pituitary during proestrus compared with those during estrus and diestrus. PNX-14 immunoreactivity in the ovary, especially during the estrus phase, was diffuse and intense in the granulosa and luteal cells and oocytes, and it was few and weak in theca cells. In addition, NUCB2/nesfatin-1 immunoreactivity was abundant and strong in granulosa and luteal cells, theca and interstitial cells, and oocytes during estrus. In the estrus phase, PNX-14 immunoreactivity was strong in the glandular epithelial cells and stromal cells of the endometrium, also NUCB2/nesfatin-1 immunoreactivity was strong in the epithelial and glandular epithelial cells. As a result, when the estrous cycle was evaluated, it was concluded that the changes in the distribution of PNX-14 and NUCB2/nesfatin-1 at all phases were related to GnRH and that these neuropeptides showed the highest immunoreactivity especially in the HPG axis and uterus tissues of estrus rats.

Reproductive and endocrine effects of artemisinin, piperaquine, and artemisinin-piperaquine combination in rats

Background:The WHO recommends artemisinin-based combination regimens for uncomplicated Plasmodium falciparum malaria. One such combination is artemisinin-piperaquine tablets (ATQ). ATQ has outstanding advantages in anti-malarial, such as good efficacy, fewer side effects, easy promotion and application in deprived regions. However, the data about the reproductive and endocrine toxicity of ATQ remains insufficient. Thus, we assessed the potential effects of ATQ and its individual components artemisinin (ART) and piperaquine (PQ) on the reproductive and endocrine systems in Wistar rats.Methods:The unfertilized female rats were intragastric administrated with ATQ (20, 40, and 80 mg/kg), PQ (15, 30, and 60 mg/kg), ART (2.5, 5, and 10 mg/kg), or water (control) for 14 days, respectively. The estrous cycle and serum levels of estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), prostaglandin (PG), and adrenocorticotropic hormone (ACTH) were determined. The weights of the kidney, adrenal gland, uterus, and ovaries were measured. The histopathological examinations of the adrenal gland, ovary, uterus, and mammary gland were performed.Results:Compared with the control group, there were no significant differences in the examined items of female rats in the ART groups, including general observation, estrous cycle, hormonal level, organ weight, and histopathological examination. The estrous cycle of female rats was disrupted within 4–7 days after ATQ or PQ administration, and then in a persistent dioestrus phase. At the end of administration, ATQ and PQ at three doses induced decreased PG, increased ACTH, increased adrenal weight and size, and pathological lesions in the adrenal gland and ovary, including vasodilation and hyperemia in the adrenal cortex and medulla as well as hyperplasia and vacuolar degeneration, ovarian corpus luteum surface hyperemia, numerous but small corpus luteum, and disordered follicle development. But the serum levels of E2, FSH, LH, and PRL did not change obviously. These adverse effects in ATQ or PQ treated rats could not completely disappear after 21 days of recovery.Conclusion:Based on the results of this study, ART had no obvious reproductive and endocrine effects on female rats, while ATQ and PQ caused adrenal hyperplasia, increased ACTH, decreased PG, blocked estrus, corpus luteum surface hyperemia, and disrupted follicle development in female rats. These events suggest that ATQ and PQ may interfere with the female reproductive and endocrine systems, potentially reducing fertility.

Lobaric acid prevents the adverse effects of tetramethrin on the estrous cycle of female albino Wistar rats.

Tetramethrin (Tm) is a commonly used pesticide that has been reported to exert estrogen-antagonistic effects selectively on female rats. The present study was undertaken to assess the protective role of lobaric acid (La) on estrous cycle in Tm-treated female Wistar rats. Female rats were exposed to Tm (50 mg/kg b.w/day) only or in combination with La at low (50 mg/kg b.w/day) or high (100 mg/kg b.w/day) dose for 30 days. The results showed that Tm altered the estrous cycle of female rats by decreasing the levels of luteinizing hormone, follicular-stimulating hormone, progesterone, estrone, and estradiol while increasing testosterone level. The morphology of vaginal smears of Tm-treated female rats showed the presence of abnormal cells and/or structures at different phases of estrus cycle. Strikingly, in (Tm + La)-treated rats, all the observed adverse effects of Tm on the hormonal parameters, cell morphology, and the length of each phase of estrous cycle were significantly diminished in a dose-dependent manner. The docking results showed that La competes with Tm for Gonadotropin-Releasing Hormone (GnRH) receptor, thereby reducing the toxicity of Tm but did not cancel the response of GnRH receptor completely. In conclusion, our results designated that La could be used as a potential candidate in the management of insecticide-induced alterations of the reproductive cycle of rodents.

Antifertility activity of Momordica dioica and Lagerstroemia speciosa in experimental rats

Agents that control fertility are termed as antifertility agents or oral contraceptives. Many plant-based products have the antifertility potential which need to be explored.The present study therefore was undertaken to evaluate possible antifertility effects of hydroalcoholic extract of fruits of (HAEMD) and aqueous extract of leaves of (AELS) in experimental rats. Experiments were carried using wistar rats of either sex. Animals were administered with different doses of HAEMD and AELS (250, and 350 mg/kg, p. o) for 30 days. The body weight and reproductive organs weights for male (Testis) and for female (Uterus) were analyzed. Sperm count and Sperm motility was determined in male rats by manually. Testosterone in male and progesterone levels in female rats were checked. Effect of both extracts on Estrous cycle in female rats were checked. Section of testis were taken for histopathological study. The effect of the extract on male rats showed decreased testis weight, reduced sperm count and motility as compared to control animals. The blood testosterone level in male rats was reduced in treatment groups. The testicular histology was altered as compared to control male rats. In female animals, extracts showed antiovulatory activity, alteration in estrous cycle, decreased uterus weight and serum progesterone levels. It is concluded that HAEMD and AELS are effective as antifertility plants for both male and female rats.

Репродуктивна токсичність тріазолових фунгіцидів ципроконазолу і епоксиконазолу при дії на самців і самиць щурів wistar у період гаметогенезу

Aim. Studying the effect of generic pesticides cyproconazole (98 %) and two samples of epoxiconazole (epoxiconazole 1 — 95,75 % and epoxiconazole 2 — 98,7 %) on the reproductive system of male and female Wistar Han rats at the level of the organism when exposed during gametogenesis, identification and characterization of their hazard, as well as assessment of the risk of reproductive toxicity of these compounds. Materials and Methods. The test samples were administered daily (5 days a week) by oral gavage at doses of 0.2 and 2.0 mg/kg for cyproconazole and 0.5 and 2.0 mg/kg for epoxiconazoles during 11 weeks for males, and 10 weeks for females. Also, there were kept intact males and females, intended for crossover mating with experimental animals. After the end of the exposure, functional indicators of the state of the gonads and the ability of animals to reproduce offspring were studied. The duration and the frequency of each stage of the estrous cycle in female rats and the number of motile sperm, the total amount of sperm and the number of abnormal forms of germ cells of the male rats were studied. The reproductive function state in females was evaluated on day 20th of pregnancy. Thereby the number of corpora lutea in the ovaries, number of alive, dead and resorbed foetuses and embryos, the foetus weight, total weight of litters were registered. The studies were carried out in accordance with the recommendations of the Bioethics Commission and the Centre’s standard operating procedures, developed in accordance with the recommendations and requirements of Good Laboratory Practice (GLP). Conclusions. Test substances at a maximum dose of 2.0 mg/kg of body weight have reproductive toxicity and endocrine-disruptive effect, exerting a significant antiandrogenic effect on males and antiestrogenic effect on female rats. No-observed-adverse-effect-level (NOАEL) for gonadal and reproductive toxicity for male and female Wistar Han rats were established. They are 0.2 mg/kg body weight for cyproconazole and 0.5 mg/kg body weight for epoxiconazole. Key Words: azole fungicides, cyproconazole, epoxiconazole, reproductive toxicity, antiandrogenic and antiestrogenic effects, Wistar Han rats.

Conversion of Testosterone to Estradiol is Necessary for the Development of Long‐term Facilitation in Adult Male Rats

Phrenic long-term facilitation (pLTF) and ventilatory long-term facilitation (vLTF) are well-defined models of respiratory neuroplasticity. In each model, acute intermittent hypoxia (AIH) stimulates persistent increases in respiratory neural drive or minute ventilation respectively. Recent findings from our laboratory indicate that sex hormones are necessary for the induction of respiratory neuroplasticity in both male and female rats. For example, AIH induced pLTF and vLTF only develop during the proestrus phase of the estrous cycle in female rats, notable for high levels of circulating 17β-estradiol, the most neuroactive form of estrogen. Removal of the ovaries (ovariectomy, OVX), the primary source of circulating sex hormones in females, also eliminates the development of pLTF and vLTF. Plasticity can be restored in OVX females with estradiol supplementation supporting a key role for estradiol signaling in development of respiratory plasticity. Testosterone, the principle sex hormone in males, is also important for development of respiratory plasticity. Male rats demonstrate reduced pLTF magnitude with aging, in correlation with reduced circulating testosterone levels, and removal of the gonads (gonadectomy, GDX) eliminates AIH-induced pLTF. Testosterone replacement is sufficient to restore pLTF in GDX male rats, but requires the activity of aromatase, the enzyme responsible for converting testosterone to estradiol, suggesting that estradiol may also play a key role in development of respiratory neuroplasticity in male rats. It is unknown whether conversion of testosterone to estradiol is necessary for development of AIH-induced plasticity in gonadally-intact male rats. To address this question, we used systemic injections of Letrozole, an aromatase inhibitor, as a first step towards determining the necessity of testosterone conversion to estradiol for development of AIH-induced respiratory neuroplasticity in gonadally-intact adult male rats. We hypothesized that aromatization of testosterone to estradiol would be necessary for induction of both AIH-induced vLTF and pLTF. Letrozole (1mg/kg), or a vehicle control, was administered subcutaneously over four days. On day three, vLTF was measured via whole-body plethysmography. On the fourth day, pLTF was quantified via phrenic nerve recordings. Researchers were blinded to treatment for all experiments and data analysis. Preliminary findings suggest that daily Letrozole injections impaired development of AIH-induced vLTF and pLTF, supporting our hypothesis. These data provide further evidence that estradiol plays a critical role in the development of respiratory neuroplasticity in both males and females.

Modulation of heroin intake by ovarian hormones in gonadectomized and intact female rats.

Heroin intake decreases during the proestrus phase of the estrous cycle in female rats. Circulating concentrations of both estradiol andprogesterone peak during proestrus, and it is not known which of these hormones, or their combination, are responsible for these effects. The purpose of this study was to determine the effects of estradiol, progesterone, and their combination on heroin self-administration in femalerats. In Experiment 1, the estrous cycle of intact female rats was tracked daily. If a rat was in proestrus, either the estrogen receptor antagonist,raloxifene, the progesterone receptor antagonist, mifepristone, or their combination was administered 30 min prior to a heroin self-administration session. InExperiment 2, separate groups of ovariectomized female rats were treated chronically with exogenous estradiol, progesterone, estradiol + progesterone, orvehicle, and heroin intake was examined over a 100-fold dose range. In Experiment 1, raloxifene, but not mifepristone, significantly blocked proestrus-associated decreases in heroin intake. In Experiment 2, estrogentreatedrats self-administered less heroin than any other group and significantly less heroin than rats treated with progesterone. These data suggest that (1) estradiol but not progesterone is responsible for proestrus-associated decreases in heroin intake and (2) estradioldecreases heroin intake relative to progesterone. These data differ from those reported previously with stimulants and suggest that estrogen-basedpharmacotherapies may be of value to women with opioid use disorder.

Estrous Cycle Modulation of Feeding and Relaxin-3/Rxfp3 mRNA Expression: Implications for Estradiol Action

Introduction: Food intake varies during the ovarian hormone/estrous cycle in humans and rodents, an effect mediated mainly by estradiol. A potential mediator of the central anorectic effects of estradiol is the neuropeptide relaxin-3 (RLN3) synthetized in the nucleus incertus (NI) and acting via the relaxin family peptide-3 receptor (RXFP3). Methods: We investigated the relationship between RLN3/RXFP3 signaling and feeding behavior across the female rat estrous cycle. We used in situ hybridization to investigate expression patterns of Rln3 mRNA in NI and Rxfp3 mRNA in the hypothalamic paraventricular nucleus (PVN), lateral hypothalamic area (LHA), medial preoptic area (MPA), and bed nucleus of the stria terminalis (BNST), across the estrous cycle. We identified expression of estrogen receptors (ERs) in the NI using droplet digital PCR and assessed the electrophysiological responsiveness of NI neurons to estradiol in brain slices. Results: Rln3 mRNA reached the lowest levels in the NI pars compacta during proestrus. Rxfp3 mRNA levels varied across the estrous cycle in a region-specific manner, with changes observed in the perifornical LHA, magnocellular PVN, dorsal BNST, and MPA, but not in the parvocellular PVN or lateral LHA. G protein-coupled estrogen receptor 1 (Gper1) mRNA was the most abundant ER transcript in the NI. Estradiol inhibited 33% of type 1 NI neurons, including RLN3-positive cells. Conclusion: These findings demonstrate that the RLN3/RXFP3 system is modulated by the estrous cycle, and although further studies are required to better elucidate the cellular and molecular mechanisms of estradiol signaling, current results implicate the involvement of the RLN3/RXFP3 system in food intake fluctuations observed across the estrous cycle in female rats.

Mid-adolescent stress differentially affects binge-like intake of sucrose across estrous cycles in female rats✰

Binge eating disorder (BED), characterized by excessive food consumption within a discrete period of time, is the most prevalent of all eating disorders, with higher rates in women than men. Chronic stress, particularly during adolescence, is a significant risk factor for BED in women, but the mechanism underlying this relationship remains elusive. We investigated the phenomenon by testing the impact of mid-adolescent intermittent physical stress (IPS) on binge-like intake of sucrose in adult female rats, assessing how the behavior changed across reproductive cycles. One hundred and nineteen Long-Evans rats were exposed to IPS (n = 59) or no stress (NS; n = 60) for 12 days during mid-adolescence (PD35–46). Binge-like eating was induced in adult animals using an intermittent access protocol: animals were provided with 12 h or 24 h access to sucrose, 12 h access to saccharin, or 12 h access to food over 28 days. After 1- or 28-day abstinence, compulsive responding for sucrose was measured using a conditioned suppression paradigm. Rats given 12 h access to sucrose developed binge-like intake, measured as increased consumption during the first hour; the effect was magnified in IPS animals and most pronounced during proestrous. Solution intake in IPS rats was predicted by open arm entries in the elevated plus maze, suggesting that increased risk-taking behavior is associated with greater binge-like eating. IPS blocked conditioned suppression after 28 days of abstinence, pointing to a role of mid-adolescent stress in compulsivity. Collectively, these findings emphasize the impact of stress on the emergence of binge eating in females and suggest that intervention programs for women with a history of adolescent adversity should be investigated as a means to reduce risk for BED.

Influence of sex, menstrual cycle, and hormonal contraceptives on egocentric navigation with or without landmarks

This study examines the influence of sex, menstrual cycle, hormonal contraceptives (HC) and sex hormone levels in following egocentric navigation instructions with or without landmarks. Estradiol seem to bias the reference frame for navigation during estrous cycle of female rats. However, previous studies in humans found no differences in overall navigation between women in their early follicular and mid-luteal menstrual cycle phases, whose performance was worse than that of men. Our study hypothesis was that the performance of women would be improved during the peri-ovulatory phase and would remain the same during placebo and active phases of HC users. The study included 21 men, 62 women with natural menstrual cycle (21 during early follicular phase, 20 during peri-ovulatory phase, and 21 during mid-luteal phase), and 38 women that were receiving HC (13 during placebo phase and 25 during active phase). The men outperformed the women with a natural menstrual cycle when following egocentric instructions without landmarks. However, the women’s performance varied according to the phase of their menstrual cycle, differing from men during early follicular and mid-luteal phases but not during the peri-ovulatory phase. The use of HC also improved the performance of women to the extent that the difference with men disappeared. No differences were observed between HC-placebo and HC-active user groups during egocentric navigation without landmarks and among all groups during egocentric navigation with landmarks. Analysis of salivary hormones showed that testosterone levels were higher in men and that estradiol levels in women were higher during peri-ovulatory and mid-luteal phases and also in HC users. Progesterone levels were higher in women during the mid-luteal phase. These results appear compatible with beneficial effect of testosterone and estradiol on egocentric navigation without landmarks and with a block of this effect produced by progesterone.

Ovarian morphometric evolution in two consecutive estrous cycles of female rats treated with steroid-free bovine follicular fluid antiserum

Ovarian morphometric evolution in two consecutive estrous cycles of female rats treated with steroid-free bovine follicular fluid antiserum

The Other 51%: An Updated Characterization of the Female Rat’s Estrous Cycle

The estrous cycle in female rats is analogous to the menstrual cycle in humans, lasting 4–5 days on average, and is composed of 4 main stages (proestrus, estrus, metestrus and diestrus) and 4 transitional stages. Each stage differs in length and is characterized by distinctive cell types with unique morphologies, which helps in the histological identification of each specific stage. Generally due to added expense and/or increased variables, animal research has historically been conducted on male animal models, and those findings are applied across the whole population.The most notable limitation in the utilization of the female animal model is the added unknown variability caused by hormonal fluctuation on the experiment. The main aim of this study was to create estrous synchronization of each experimental cohort, limiting the introduction of these variables. Although group housing has been shown to induce spontaneous synchronization (in mice), the inability to select for a specific stage, as well as limited success in rats, required an alternative method. We used luteinizing hormone‐releasing hormone analog (LHRHa) one week prior to exposure to induce estrous synchronization. Estrous stage was assessed via vaginal lavage and crystal violet staining. Slide comparisons of lavage cells collected prior to and after chemical manipulation showed differences in quantity and/or morphology of cells in each stage. In our study, we targeted a successful synchronization to the diestrus stage at 168 hours post‐injection. In our assessment of over 140 animals, we found that synchronization was successful 49.3% of the time. Overall, the use of LHRHa to induce estrous synchronization maximized experimental time management and limited estrous‐cycle‐dependent physiological and metabolic changes, enabling biochemical data to be collected and interpreted with minimal extraneous variables. These data are extremely beneficial to the drug discovery process, as researchers now look for more gender‐balanced models to assess new therapeutics.DISCLAIMERSThe views expressed in this poster are those of the author(s) and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government. The experimental protocol was approved by the Animal Care and Use Committee at the United States Army Medical Research Institute of Chemical Defense, and all procedures were conducted in accordance with the principles stated in the Guide for the Care and Use of Laboratory Animals (National Research Council, 2011), and the Animal Welfare Act of 1966 (P.L. 89–544), as amended.

Estrous Cycle Study Regarding Alcohol Use Disorder Through Endostatin Treatment

Alcohol Use disorder has been defined as the chronic relapsing brain with an inability to stop or control alcohol use despite adverse social, occupational, or health consequences. 17 million Americans have met the criteria to be diagnosed as having moderate to severe alcohol use disorder in the past decade. Relapse to alcohol seeking has become a public health concern.An increased amount of PECAM‐1 in the medial Prefrontal Cortex has been shown to be linked to enhanced reinstatement of alcohol seeking. It was hypothesized that endostatin would decrease PECAM‐1 in the mPFC. It was also hypothesized that changes in the behaviour of female rodents with ethanol dependence who were treated using endostatin would be linked to their estrous cycles. Saline was used as the control vehicle in this experiment and endostatin as the variable. The rodents were divided into a control group with no alcohol dependence, a group with no alcohol dependence who were administered endostatin, and a group which was alcohol dependant who were also administered endostatin. Alcohol dependence was established by exposing the rats to ethanol vapor.The results found that in rodents with alcohol dependence, endostatin reduced relapse to drinking in female rats. The estrous cycle in female rats is comparable to menstruation in female humans. However, in rats, there are four phases: proestrus, estrous, metestrous, and diestrus. Estrous phase sample stains showed that Endostatin was not responsible for the changes in estrous phases. There was however, a significant change in estrous phases of rats with any form of alcohol consumption. Future research on this project will determine the underlying mechanisms of how exactly alcohol is able to alter the estrous cycles of rats. It will also determine the role of estrous phases in alcohol dependence. Additionally, endostatin can be research as a viable treatment for alcohol use disorder.Support or Funding InformationUCSD STARS Program ]MARC U STAR CSUB NIHFigure 3. (left panel); Drinking behavior in CIE female and male rats during baseline, CIE and relapse to drinking sessions. Female rats have higher ethanol intake during baseline sessions and this difference did not persist during CIE. There was a trend towards higher response during relapse session in females (right panel); Drinking behavior in CIE female and male rats during relapse session with or without endostatin treatment. There was a significant sex × endostatin interaction F (3, 93) = 2.751, p=0.04 and main effect of endostatin treatment F (3, 93) = 4.05, p&lt;0.05 with females showing reduced drinking during relapse sessions after endostatin treatment. N=6 to 13 rats in each group. Data is expressed as mean +/− SEM.Figure 1Figure 2. (left panel); Drinking behavior in ED female and male rats during baseline, maintenance and relapse to drinking sessions. Female rats have higher ethanol intake during baseline sessions and this difference did not persist during maintenance. There were no differences during relapse session between males and females. (right panel); Drinking behavior in ED female and male rats during relapse session with or without endostatin treatment. There was no significant effect of endostatin in either sexes tested. N=6 to 13 rats in each group. Data is expressed as mean +/− SEM.Figure 2