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Estrous Cycle

The estrous cycle is the recurring physiological changes that are induced by reproductive hormones in most mammalian thfemales.
It consists of a series of stages that prepare the uterus for implantation of a fertilized egg.
The cycle typicaly lasts 4-5 days in rodents and varies in length across different species.
Proper understanding and optimization of the estrous cycle is critical for reproductive research and animal models.
PubCompare.ai can help reseachers easily locte protocols and identify the best methods for studying this important biological process.

Most cited protocols related to «Estrous Cycle»

Vaginal Cytology for Mouse Estrous Cycle

Cited 110 times

A vaginal swab was collected using a cotton tipped swab (Puritan Medical Products Company, LLC Guilford, ME) wetted with ambient temperature physiological saline and inserted into the vagina of the restrained mouse. The swab was gently turned and rolled against the vaginal wall and then removed. Cells were transferred to a dry glass slide by rolling the swab across the slide. The slide was air dried and then stained with approximately 400 µL of stain (Accustain, Sigma-Aldrich, St. Louis, MO) for 45 seconds. The slides were rinsed with water, overlaid with a coverslip, and viewed immediately at 200× magnification under bright field illumination. The stage of the estrous cycle was determined based on the presence or absence of leukocytes, cornified epithelial, and nucleated epithelial cells according to Felicio, et al [9] (link).
When the female is in proestrus, mostly nucleated and some cornified epithelial cells are present. Some leukocytes may be present if the female is in early proestrus. As the stage of the cycle advances to estrus, mostly cornified epithelial cells are present. If the cycle is not interrupted by pregnancy, pseudopregnancy, or other phenomena, metestrus will begin. Metestrus is a brief stage when the corpora lutea form but fail to fully luteinize due to a lack of progesterone. The uterine lining will begin to slough and evidence of this is seen in the form of cornified eipithelial cells and polymorphonuclear leukocytes present in vaginal swabs. Some nucleated epithelia cells will also be present in late metestrus. Diestrus is the longest of the stages lasting more than 2 days. Vaginal swabs during diestrus show primarily polymorphonuclear leukocytes and a few epithelial cells during late diestrus. Leukocytes remain the predominant cell type having removed cellular debris. The cycle then repeats.

Byers S.L., Wiles M.V., Dunn S.L, & Taft R.A. (2012). Mouse Estrous Cycle Identification Tool and Images. PLoS ONE, 7(4), e35538.

Publication 2012

Cells Corpus Luteum Diestrus Epithelial Cells Epithelioid Cells Estrous Cycle Estrus Gossypium Granulocyte Leukocytes Lighting Metestrus Mus Neoplasm Metastasis physiology Pregnancy Proestrus Progesterone Pseudocyesis Saline Solution Stains Uterus Vagina Vision Woman

Ovulation Assessment in Mice

Cited 54 times

After the stage of the estrous cycle was determined, each mouse was paired with one CByB6F1/J male and the following morning the presence or absence of a vaginal plug was noted and each mouse was euthanized by cervical dislocation. The contents of the oviducts were flushed using M2 media into a petri dish to look for oocytes as evidence that ovulation had occurred.

Byers S.L., Wiles M.V., Dunn S.L, & Taft R.A. (2012). Mouse Estrous Cycle Identification Tool and Images. PLoS ONE, 7(4), e35538.

Publication 2012

Estrous Cycle Hyperostosis, Diffuse Idiopathic Skeletal Joint Dislocations Males Mice, House Neck Oviducts Ovulation Ovum Vagina

Identifying Estrous Cycle Stages in Mice

Cited 46 times

Representative photographs and micrographs for each stage of the estrous cycle were obtained following these steps: 1. a preliminary observation was made about the stage of the estrous cycle by assessing the vaginal opening of each mouse, 2. the stage of the estrous cycle was verified by vaginal cytology, 3. stage of estrous cycle was confirmed by mating mice overnight and checking for ovulation the following morning as described later.
These steps can also be used to learn the visual method and train the eye to identify each stage. Proestrus and estrus are easier to identify by visual observation than metestrus and diestrus. Coat color and skin pigmentation can make it more challenging to evaluate some strains. It is easier to observe changes in agouti and albino strains than in black strains where changes to the vaginal opening are more subtle.

Byers S.L., Wiles M.V., Dunn S.L, & Taft R.A. (2012). Mouse Estrous Cycle Identification Tool and Images. PLoS ONE, 7(4), e35538.

Publication 2012

Albinism Cuniculus Cytological Techniques Diestrus Estrous Cycle Estrus Metestrus Mice, House Ovulation Proestrus Skin Pigmentation Strains Vagina

Molecular Mechanisms of Anxiety Behavior

Cited 35 times

The animal studies were conducted in accordance with the guidelines of the European Union (Council of the European Communities Directive 2010/63/EU) and were approved by the Institutional Animal Care and Use Committee and local authorities (Government of Upper Bavaria). The HAB and LAB animals, which spent <15% (HAB) or >60% (LAB) of the total test time on one of the open arms of the EPM were bred for over 45 generations in the animal facility of the Max Planck Institute of Psychiatry (MPIP). Suitable numbers of HAB×LAB crosses were made to receive F1 offspring for behavioral and molecular studies. CD-1 and C57BL/6 J mice were purchased from Charles River (Sulzfeld, Germany). Unlike CD-1 mice, C57BL/6 J is an inbred mouse strain and is the preferred choice for AAV experiment because of its relatively homogenous genetic background and little phenotypic variability. Thus, any difference in phenotype can be traced back to the respective treatment. All animals were housed under optimal conditions, i.e., a temperature of 23 ± 2°C, a relative air humidity of 60 ± 5% and a 12/12-h light–dark cycle with beginning of the light phase at 8 AM and had access to food pellets (Altromin GmbH, Lage, Germany) and tap water ad libitum. Only male mice were utilized for this study to avoid potential difference in behavioral or molecular effects when female mice are in different stages of estrous cycle. All the behavioral experiments were performed between 08:30 and 11:30 A.M.

Naik R.R., Sotnikov S.V., Diepold R.P., Iurato S., Markt P.O., Bultmann A., Brehm N., Mattheus T., Lutz B., Erhardt A., Binder E.B., Schmidt U., Holsboer F., Landgraf R, & Czibere L. (2018). Polymorphism in Tmem132d regulates expression and anxiety-related behavior through binding of RNA polymerase II complex. Translational Psychiatry, 8, 1.

Publication 2018

A(2)C Animals Arm, Upper Estrous Cycle Females Food Genetic Background Homozygote Humidity Institutional Animal Care and Use Committees Males Mice, House Mice, Inbred C57BL Mice, Inbred Strains Pellets, Drug Phenotype Rivers

Evaluating Mouse Estrous Cycle Visually

Cited 34 times

To evaluate the stage of the estrous cycle by visual observation, each mouse was held by the tail with the forepaws resting on a cage lid. The vaginal opening of each female was evaluated based on the criteria described by Champlin, et al. A digital image of each mouse was taken using a DSCF707 Cyber-shot digital camera (Sony, Japan). Additional lighting was supplied for photographs by fiber optic lights (Fiber Lite MI-150, Dolan-Jenner Industries, Boxborough, MA).
When evaluating stage of the estrous cycle using the visual method, it is important to always evaluate animals in the same area with respect to room lighting. The table or workstation should always face the same direction and there should be sufficient light available. The light source is also important to consider because it can change the perceived color of vaginal tissues and make evaluation difficult. Portable lights can be purchased and attached to workstations and moved as needed. However, LED lights should be avoided because they have a purple hue that makes visual detection challenging. Battery operated 4W fluorescent lamps (Maverick, Edison, NJ) were used in the vivarium for this study. In the laboratory, 32W Sylvania Octron fluorescent ceiling lights (Sylvania, Danvers, MA) were used for lighting.
The vaginal opening of mice in proestrus is characterized by swollen, moist, pink tissue. The opening is wide and there are often wrinkles or striations along the dorsal and ventral edges. As the mouse enters estrus the vaginal opening becomes less pink, less moist, and less swollen. Metestrus is characterized by a vaginal opening that is not open wide, not swollen, and white cellular debris may be visible. In diestrus, the vaginal opening is small and closed with no tissue swelling.

Byers S.L., Wiles M.V., Dunn S.L, & Taft R.A. (2012). Mouse Estrous Cycle Identification Tool and Images. PLoS ONE, 7(4), e35538.

Publication 2012

Animals ARID1A protein, human Diestrus Estrous Cycle Estrus Face Females Fibrosis Fingers Leukocytes Light Metestrus Mice, House Proestrus Tail Tissues Vagina

Most recents protocols related to «Estrous Cycle»

Estrous Cycle Assessment in Female Mice

Estrous cycles were assessed at the same time every day during behavioral study performance day following published protocols [53 (link), 54 (link)]. Female mice were properly handled to minimize stress, by gently lifting the animal by the base of tail a plastic pipette filled with about 1 ml of PBS was placed on the tip of the vagina and flushed 5 times with same PBS to allow proper collection of samples for vaginal cytology. Sample was then smeared on appropriate labeled microscope slides and after 1 h of drying time, a crystal violet (0.1%) staining was performed on slides. After drying, the slides were observed under a light microscope to visualize cells. Images were obtained using NIS Elements imaging software version 4.0.

Archie S.R., Sifat A.E., Zhang Y., Villalba H., Sharma S., Nozohouri S, & Abbruscato T.J. (2023). Maternal e-cigarette use can disrupt postnatal blood-brain barrier (BBB) integrity and deteriorates motor, learning and memory function: influence of sex and age. Fluids and Barriers of the CNS, 20, 17.

Publication 2023

Animals Cells Cytological Techniques Estrous Cycle Females Light Microscopy Microscopy Mus Specimen Collection Tail Vagina Violet, Gentian

Genetic Characterization of Cholinergic Neurons in Fear Conditioning

All animal treatments and procedures were in compliance with the American Association for Laboratory Animal Science (AALAS) and experimental procedures were approved by both the University of South Carolina and Columbia VA Health Care System Institutional Care and Use Committees. Upon arrival, rats were maintained in the vivarium on a 12‐hour light/dark cycle with ad libitum access to food and water. As Long Evans Tg (ChAT::Cre) rats originally developed by the Deisseroth group have genetically‐restricted expression of Cre recombinase in cholinergic (ChAT expressing) neurons,²⁶ four ChAT:Cre hemizygous male rats were purchased from the Rat Resource and Research Center (RRRC# 00658: Long Evans‐Tg(ChAT‐Cre)5.1Deis; University of Missouri, Columbia MO; RRID:RRRC_00658) and were ~ 2 months of age upon arrival. They were bred with four adult female wildtype Long Evans rats (~2 months old on arrival; Envigo RRID:RGD_5508398). The day before weaning, rat pups were color coded by tail marking and each given a unique number. At 21 days, the four resulting litters (N = 41 pups) were weaned. At weaning, tail snips were taken (~1 mm) with a sterile scalpel and placed into a labeled 96 well plate (provided by TransnetYX). The plate was sealed and sent to TransnetYX (Cordova, TN) for genotyping using polymerase chain reaction (PCR) for detection of the Cre recombinase gene.
Following weaning, animals were housed in groups of 2–3 with same‐sex littermates, but were single housed starting ~2 weeks prior to behavioral testing per our previous studies.¹⁷, ⁴², ⁴³ Breeding of the transgenic ChAT::Cre+ males with wildtype females yielded 41 offspring that were tested in a cue‐conditioned fear and extinction protocol during early light phase of the light: dark cycle (see Figure 1; as described in¹⁷, ⁴², ⁴³). The groups tested were Cre+ males (N = 12), Cre‐ males (N = 8), Cre+ females (N = 15), and Cre‐ females (N = 6). Unfortunately, due to the COVID‐19 pandemic we were unable to add additional litters to create similar sample sizes in each group.
Males and females were handled for 2 weeks prior to behavioral testing, and daily vaginal lavage was performed in the females to determine estrous cycle stage; males were handled similarly. Vaginal lavage was also performed after behavioral testing each day to assess the stage of the cycle during each behavioral test while avoiding additional handling stress.⁴³, ⁴⁴, ⁴⁵ Vaginal cytology was determined using the fresh cytology samples under a microscope, and slides were then fixed using 95% ethanol for additional staining using hematoxylin and eosin for additional verification (see Refs. 43 (link), 44 (link) for detailed methods).

Tryon S.C., Sakamoto I.M., Kaigler K.F., Gee G., Turner J., Bartley K., Fadel J.R, & Wilson M.A. (2023). ChAT::Cre transgenic rats show sex‐dependent altered fear behaviors, ultrasonic vocalizations and cholinergic marker expression. Genes, Brain, and Behavior, 22(1), e12837.

Publication 2023

Animals Animals, Transgenic Behavior Test Cholinergic Agents COVID 19 Cre recombinase Cytological Techniques Eosin Estrous Cycle Ethanol Extinction, Psychological Fear Females Food Genes Hematoxylin Hemizygote Light Males Microscopy Neurons Patient Holding Stretchers Polymerase Chain Reaction Rats, Long-Evans Sterility, Reproductive Tail Vagina Vaginal Douching Woman

Premature Ovarian Failure in FMR1 Mice

All animal procedures were performed with the approval from the University of California (Riverside, CA) Animal Care and Use Committee and in accordance with the National Institutes of Health Animal care and Use Guidelines. Breeding pairs of FVB.129P2-Fmr1tm1Cgr/J (Fmr1 KO) and their congenic controls (WT) mice were obtained from Jackson Laboratories and bred in-house. Mice were maintained under a 12-h light, 12-h dark cycle and received food and water ad libitum. Since we were interested in determining the mechanisms of premature ovarian failure in women with mutations in the FMR1 gene, only female mice were used for our studies. Estrous cycle stage was determined with vaginal smears and females were collected in a specific estrous cycle stage, as indicated for each analysis. For fertility studies, Fmr1 KO females and WT controls were housed with WT males and their litters and numbers of pups per litter were recorded. Ovariectomy was performed, as described before, using 8-week-old mice (43 (link)). Animals were allowed to recover and seven days later blood was collected for hormone analyses as described below.

Villa P.A., Lainez N.M., Jonak C.R., Berlin S.C., Ethell I.M, & Coss D. (2023). Altered GnRH neuron and ovarian innervation characterize reproductive dysfunction linked to the Fragile X messenger ribonucleoprotein (Fmr1) gene mutation. Frontiers in Endocrinology, 14, 1129534.

Publication 2023

Animals BLOOD Estrous Cycle Females Fertility Food Genes Hormones Light Males Mice, House Mutation Ovarian Failure, Premature Ovariectomy Patient Holding Stretchers Vaginal Smears Woman

Uterine Remodeling during Porcine Pregnancy

Twelve healthy and disease-free Yorkshire sows (parity 2) were purchased from Wen's Foodstuffs Group Co., Ltd. (Yunfu, China). All sows were randomly divided into two groups: cyclic (n = 3) and pregnant (n = 9). All animals were examined for estrus twice a day, and those in the pregnant group were artificially inseminated with a standard dose of single Yorkshire semen after estrus. By contrast, those in the cyclic group were artificially inseminated with dead semen from the same boar. On day 9 of the estrous cycle (9C, n = 3) and days 9, 12, and 15 of pregnancy (9P, 12P, and 15P, n = 3 sows/day of pregnancy), sows were slaughtered at a nearby slaughterhouse. The uterus was extracted swiftly and transported to the laboratory in an icebox. Approximately 1 cm² of uterine section samples were collected from each uterine horn on the antimesometrial side of uterus. They were quickly fixed in 10% neutral-buffered formalin for 24 h for paraffin embedding (FFPE), hematoxylin–eosin (H&E) staining, periodic acid-Schiff (PAS) staining, and immunohistochemistry (IHC). Each uterine horn was flushed with 200 mL sterile phosphate-buffered saline (PBS, pH = 7.2), and pregnancy was established by the appearance of normal spherical (day 9 of pregnancy) or filamentous embryos (days 12 and 15 of pregnancy) (Additional file 1: Fig. S1). The media were centrifuged at 4000×g for 5 min to remove cell debris. For subsequent tests, the embryos or uterine luminal fluid samples were quickly frozen in liquid nitrogen and preserved at − 80 °C.

Hong L., Zang X., Hu Q., He Y., Xu Z., Xie Y., Gu T., Yang H., Yang J., Shi J., Zheng E., Huang S., Xu Z., Liu D., Cai G., Li Z, & Wu Z. (2023). Uterine luminal-derived extracellular vesicles: potential nanomaterials to improve embryo implantation. Journal of Nanobiotechnology, 21, 79.

Publication 2023

Animals Cells Cytoskeletal Filaments Embryo Eosin Estrous Cycle Estrus Formalin Freezing Immunohistochemistry Nitrogen Periodic Acid Phenobarbital Phosphates Pigs Plant Embryos Pregnancy Saline Solution Sterility, Reproductive Uterine Cornua

Skeletal Development in Wild-type and Integrin-null Mice

All methods were approved by the University of Guelph Animal Care Committee (AUP#3655). Skeletally mature (18 ± 2 weeks) wild-type and itga1-null [8 (link)], female and male BALB/c mice (n = 3 per group) were selected for experiments from breeding colonies at the University of Guelph. Genotype was determined through a multiplex polymerase chain reaction using DNA extracted from ear notches. Mice were weighed [mean ± standard deviation; wild-type female (28.1 ± 1.2 g) and male (31.1 ± 2.1 g), itga1-null female (27.4 ± 1.6 g) and male (33.0 g ± 2.2 g)] then anesthetized with isoflurane and euthanized by cardiac puncture followed by cervical dislocation [23 ]. Estrous cycle stage at euthanasia was not controlled.

Black A.L., Haskins J., Pozzi A, & Clark A.L. (2023). Sexual dimorphism in reactive oxygen species production and a role for integrin α1β1 in estrogen receptor α and β expression in articular cartilage. Journal of Orthopaedic Surgery and Research, 18, 170.

Publication 2023

Animal Care Committees Estrous Cycle Euthanasia Females Genotype Heart Isoflurane Joint Dislocations Males Mice, House Mice, Inbred BALB C Multiplex Polymerase Chain Reaction Neck Punctures

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More about "Estrous Cycle"

The estrous cycle, also known as the oestrous cycle, is a recurring physiological process in female mammals that is driven by reproductive hormones.
This cycle consists of a series of stages that prepare the uterus for the potential implantation of a fertilized egg.
Typically, the estrous cycle lasts 4-5 days in rodents like Sprague-Dawley rats and C57BL/6J mice, but the duration can vary across different species.
Proper understanding and optimization of the estrous cycle is critical for reproductive research and animal models.
Researchers can utilize various techniques and tools to study this important biological process, such as Power SYBR Green PCR Master Mix, Depo-Provera, and the StepOnePlus system.
Additionally, analyzing data with software like GraphPad Prism 5 can provide valuable insights.
For male Sprague-Dawley rats and C57BL/6 mice, the estrous cycle is also an important consideration, as it can impact research findings and experimental designs.
Researchers may need to account for the stage of the cycle when working with these animal models.
Optimizing the estrous cycle research is essential for enhancing reproducibility and accuracy.
PubCompare.ai, the leading AI-driven platform, can assist researchers in easily locating protocols from literature, preprints, and patents, and using AI-driven comparisons to identify the best protocols and products for their specific needs.
This can help researchers streamline their estrous cycle studies and improve the overall quality of their reproductive research.