Mouse Estrous Cycle

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Reproductive processes in female mammals are characterised by cyclic alterations in the female tract and in sexual receptivity. The recurrent period of receptivity, or "heat" is called Estrus. The estrous cycle has been most extensively studied in laboratory rodents (mice and rats). Rats kept separate from males in the laboratory repeat the Estrous cycle throughout the year at intervals of about five days, unless subjected to pregnancy, pseudo-pregnancy (after a sterile mating), or disease. The cycle involves the whole of the reproductive tract, and it is possible to determine the sexual status of the female rat by examination of smears prepared from the vaginal fluid.

Rats and mice are examples of polyestrus mammals (as are cats which are seasonally polyoestrus). Monestrus forms (most wild animals - foxes, bears, wolves etc.) complete a single estrous cycle annually. In the wild, rats and mice probably suspend the cycle for a period during the winter; the reproductive organs are in a state of quiescence, called anestrus.

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Some Recent Findings

Mouse estrous cycle stage identification
Mouse estrous cycle stage identification[1]
  • Mouse estrous cycle identification tool and images[1] "The efficiency of producing timed pregnant or pseudopregnant mice can be increased by identifying those in proestrus or estrus....Presented here are a series of images of the vaginal opening at each stage of the estrous cycle for 3 mouse strains of different coat colors: black (C57BL/6J), agouti (CByB6F1/J) and albino (BALB/cByJ). When all 4 stages (proestrus, estrus, metestrus, and diestrus) need to be identified, vaginal cytology is regarded as the most accurate method. An identification tool is presented to aid the user in determining the stage of estrous when using vaginal cytology. These images and descriptions are an excellent resource for learning how to determine the stage of the estrous cycle by visual observation or vaginal cytology."
  • Refining timed pregnancies in two strains of genetically engineered mice. [2]"In both sEHKO and GFP colonies, increases in body weight at 1 and 2 weeks after timed male exposure more reliably and consistently indicated pregnancy than did plug detection."
  • Assessing reproductive status/stages in mice. [3]
  • Uterine NK cells in murine pregnancy. [4]"Murine uterine natural killer (uNK) cells are transient, short-lived, terminally differentiated lymphocytes found in decidualized endometrium. ....Activated uNK cells are now considered critical for appropriate endometrial angiogenesis in early implantation site development and in non-gestational endometrium."
  • Corpus luteum development: lessons from genetic models in mice.[5] "The life span and function of the corpus luteum is regulated by complex interactions between stimulatory (luteotrophic) and inhibitory (luteolytic) mediators. ... In rodents, prolactin is the major luteotrophic hormone by maintaining the structural and functional integrity of the corpus luteum for several days after mating. Other factors involved in steroidogenesis, control of cell cycle, apoptosis, and tissue remodeling have been shown to play a role in corpus luteum development and maintenance. Especially, PGF2alpha seems to be the most potent luteolytic hormone."
  • Methodologies to study implantation in mice.[6] "....The process of implantation can be postponed and reinstated experimentally by manipulating ovarian estrogen secretion. Stromal decidualization can also be induced experimentally in the hormonally prepared uterus in response to stimuli other than the embryo. ...This chapter describes the routine laboratory methodologies to study the events of early pregnancy, with special emphasis on the implantation process in mice."
More recent papers  
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This table shows an automated computer PubMed search using the listed sub-heading term.

  • Therefore the list of references do not reflect any editorial selection of material based on content or relevance.
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References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

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Search term: Mouse Estrous Cycle

Valesca B Luz, Ivana Cristina N Gadelha, Luiz Augusto V Cordeiro, Marília M Melo, Benito Soto-Blanco In vitro study of gossypol's ovarian toxicity to rodents and goats. Toxicon: 2018; PubMed 29501827

Zhang-Dong Xie, Yi-Min Guo, Mei-Juan Ren, Jichun Yang, Shao-Fang Wang, Tong-Hui Xu, Li-Ming Chen, Ying Liu The Balance of [Formula: see text] Secretion vs. Reabsorption in the Endometrial Epithelium Regulates Uterine Fluid pH. Front Physiol: 2018, 9;12 PubMed 29422866

Xin-Yuan Cao, Xu Hua, Jian-Wei Xiong, Wen-Ting Zhu, Jun Zhang, Ling Chen Impact of Triclosan on Female Reproduction through Reducing Thyroid Hormones to Suppress Hypothalamic Kisspeptin Neurons in Mice. Front Mol Neurosci: 2018, 11;6 PubMed 29403355

Maria Yousaf, Hina Siddiqi, Nazish Waheed Histomorphological Effects Of Hunger Stress On Ovaries. J Ayub Med Coll Abbottabad: 2018, 29(4);654-657 PubMed 29330998

James R Day, Anu David, Alexa L Cichon, Tanay Kulkarni, Marilia Cascalho, Ariella Shikanov Immunoisolating poly(ethylene glycol) based capsules support ovarian tissue survival to restore endocrine function. J Biomed Mater Res A: 2018; PubMed 29318744

Mouse Estrous Cycle

Diestrus Small follicles only are present with large corpora lutea from the previous ovulation. These secrete for only a very short time unless pregnancy or pseudopregnancy intervene. Small and anaemic, low motility, lumen small and slit-like. Cells of the uterine mucosa columnar; polymorphonuclear leucocytes in stroma; endometrial glands collapsed, atrophic. Epithelium thin, mitotic figures infrequent. Leucocytes abundant in stroma, migrate through the epithelium into vaginal lumen. Stringy mucous in which are entangled many leucocytes and a few nucleated epithelial cells.
Proestrus Some follicles grow rapidly. Become more vascular, water content increases, organ distends. Contractility more pronounced. Epithelial cells become higher (continuing into estrus). Leucocytes disappear from mucosa. Endometrial glands hypertrophy. Epithelum thickens, numerous mitoses in inner layers. Old layers of epithelium line the lumen. Leucocytes no longer migrate through the epithelium. Superficial epithelial cells slough off into lumen. Largely small, round, nucleated epithelial cells, singly or in sheets. None to few leucoytes.
Estrus Ovulation in the rat is spontaneous and occurs about 10 hours after the beginning of estrus. "Heat" (receptivity) lasts about 13 hours. Usually 10-20 eggs ovulated each time. gains maximum vascularisation. Epithelial cells reach maximum development. No leucocytes. Outer layer of epithelial cells become cornified and sloughed into the lumen. In early estrus these cells retain their nuclei, but in later stages no nuclei visible and the cells are irregular, flat, cornified plates. The skin around the vaginal orifice becomes swollen. Contains hundreds of large cornified cells (squames) with degenerate nuclei. Towards the end of estrus the smear becomes "cheesy" - masses of adherent cornified cells.
Metestrus Many corpora lutea, which secrete only for a very short time, and small follicles. Epithelium continues vacuolar degeneration and replacement. Leucocytes in stroma. Decrease in size and vascularity. Deeper layers of the estrous epithelium now line the lumen, the older, superficial layers having become cornified and sloughed off. Reduction of mitotic activity in epithelium. Leucocytes in stroma and migrating through the epithelium into the lumen. Many leucocytes and a few cornified cells.

Mouse Ovarian Follicle Size

Mouse ovarian follicle size.jpg

Image Source: High-resolution ultrasound biomicroscopy for monitoring ovarian structures in mice. [7]

Histological Features

For more detailed histological information see [#Champlin Champlin etal., 1973].

Uterus The changes in the uterus may not be particularly well-marked.

  1. Histological changes in the luminal epithelium
  2. Histological changes in the glandular epithelium
  3. Secretory activity of uterine glands
  4. Changes in stromal cells, e.g. number of leucocytes
  5. Overall changes in the size distention and shape of the lumen.

Vagina Note the changes in the vaginal epithelium.

  1. The number of mitotic figures
  2. The number of layers in the epithelium
  3. The amount of cornification, and the changes from live to dead cells.
  4. Surface mucus coating the epithelium
  5. Presence or absence of infiltrating polymorphonuclear leucocytes.

Vaginal Smears

Relate the appearance of the smears to the sections of the vagina, noting particularly the composition of cells in the smear and the vaginal epithelium.

1. Relative numbers and appearance of cell types - epithelial and polymorphs.

2. Presence of mucus.

Carnegie Stage Species Comparison

Mouse Stages: E1 | E2.5 | E3 | E3.5 | E4.5 | E5.0 | E6.0 | E7.0 | E7.5 | E8.0 | E8.5 | E9.0 | E9.5 | E10 | E10.5 | E11 | E11.5 | E12 | E12.5 | E13 | E13.5 | E14 | E14.5 | E15 | E15.5 | E16 | E16.5 | E17 | E17.5 | E18 | E18.5 | E19 | E20 | Timeline | About timed pregnancy

Species Stage
Human Days 1 2-3 4-5 5-6 7-12 13-15 15-17 17-19 20 22 24 28 30 33 36 40 42 44 48 52 54 55 58
Mouse Days 1 2 3 4 5.0 6.0 7.0 8.0 9.0 9.5 E10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16
Rat Days 1 3.5 4-5 5 6 7.5 8.5 9 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17 17.5
Note these Carnegie stages are only approximate day timings for average of embryos. Links: Carnegie Stage Comparison

O'Rahilly R. (1979). Early human development and the chief sources of information on staged human embryos. Eur. J. Obstet. Gynecol. Reprod. Biol. , 9, 273-80. PMID: 400868

The House Mouse: Atlas of Mouse Development by Theiler Springer-Verlag, NY (1972, 1989). | online book
OTIS EM & BRENT R. (1954). Equivalent ages in mouse and human embryos. Anat. Rec. , 120, 33-63. PMID: 13207763

Witschi, E. (1962) Development: Rat. In: Growth Including Reproduction and Morphological Development. Altman, P. L. , and D. S. Dittmer, ed. Fed. Am. Soc. Exp. Biol., Washington DC, pp. 304-314.
Pérez-Cano FJ, Franch À, Castellote C & Castell M. (2012). The suckling rat as a model for immunonutrition studies in early life. Clin. Dev. Immunol. , 2012, 537310. PMID: 22899949 DOI.


  1. 1.0 1.1 Shannon L Byers, Michael V Wiles, Sadie L Dunn, Robert A Taft Mouse estrous cycle identification tool and images. PLoS ONE: 2012, 7(4);e35538 PubMed 22514749 | [ PLoS One.
  2. Sarah L Mader, Nicole L Libal, Kathleen Pritchett-Corning, Rui Yang, Stephanie J Murphy Refining timed pregnancies in two strains of genetically engineered mice. Lab Anim (NY): 2009, 38(9);305-10 PubMed 19701181
  3. Claudia S Caligioni Assessing reproductive status/stages in mice. Curr Protoc Neurosci: 2009, Appendix 4;Appendix 4I PubMed 19575469
  4. M J Bilinski, J G Thorne, M J Oh, S Leonard, C Murrant, C Tayade, B A Croy Uterine NK cells in murine pregnancy. Reprod. Biomed. Online: 2008, 16(2);218-26 PubMed 18284876
  5. Anne Bachelot, Nadine Binart Corpus luteum development: lessons from genetic models in mice. Curr. Top. Dev. Biol.: 2005, 68;49-84 PubMed 16124996
  6. Kaushik Deb, Jeff Reese, Bibhash C Paria Methodologies to study implantation in mice. Methods Mol. Med.: 2006, 121;9-34 PubMed 16251731
  7. Rajesh S Jaiswal, Jaswant Singh, Gregg P Adams High-resolution ultrasound biomicroscopy for monitoring ovarian structures in mice. Reprod. Biol. Endocrinol.: 2009, 7;69 PubMed 19580664 | PMC2714516


Michelle C Cora, Linda Kooistra, Greg Travlos Vaginal Cytology of the Laboratory Rat and Mouse: Review and Criteria for the Staging of the Estrous Cycle Using Stained Vaginal Smears. Toxicol Pathol: 2015; PubMed 25739587

Charles L Chaffin, Catherine A Vandevoort Follicle growth, ovulation, and luteal formation in primates and rodents: a comparative perspective. Exp. Biol. Med. (Maywood): 2013, 238(5);539-48 PubMed 23856905


Yong-Jun Yang, Yu-Jing Cao, Shu-Min Bo, Sha Peng, Wei-Min Liu, En-Kui Duan Leptin-directed embryo implantation: leptin regulates adhesion and outgrowth of mouse blastocysts and receptivity of endometrial epithelial cells. Anim. Reprod. Sci.: 2006, 92(1-2);155-67 PubMed 16023802

Kaushik Deb, Jeff Reese, Bibhash C Paria Methodologies to study implantation in mice. Methods Mol. Med.: 2006, 121;9-34 PubMed 16251731

Dong-Soo Lee, Yoshiko Yanagimoto Ueta, Xuenan Xuan, Ikuo Igarashi, Kozo Fujisaki, Chihiro Sugimoto, Yutaka Toyoda, Hiroshi Suzuki Expression patterns of the implantation-associated genes in the uterus during the estrous cycle in mice. J. Reprod. Dev.: 2005, 51(6);787-98 PubMed 16210782

Pei Su, Joyce C Wu, Jeffrey R Sommer, A Jesse Gore, Robert M Petters, William L Miller Conditional induction of ovulation in mice. Biol. Reprod.: 2005, 73(4);681-7 PubMed 15917351

A K Champlin, D L Dorr, A H Gates Determining the stage of the estrous cycle in the mouse by the appearance of the vagina. Biol. Reprod.: 1973, 8(4);491-4 PubMed 4736343

Search PubMed

Search PubMed: mouse estrous cycle | estrous cycle | mouse anestrus | oestrous cycle


  • a disintegrin and metalloproteinase - (ADAM) a large family (-8, -9, -10, -12, -15 and -17) of secreted proteins suggested to be involved in remodelling mouse uterine tissue during the oestrous cycle.
  • anestrus - lack of a normal estrus cycle.
  • Bruce Effect - pheromones from a strange male can prevent embryo implantation in recently bred female.
  • calling behaviour - vocalization, vocal communication sounds associated with reproductive behaviour in several species.
  • Lee-Boot Effect - female mice housed together (in groups) results in a synchronization of their estrus cycles. In addition, the extended absence of male pheromones leads to a state of anestrus (lack of a normal estrus cycle).
  • major urinary proteins - (MUPs) proteins which carry volatile substances, including pheromones, and protect them during their internal passage (liver to kidneys into urine).
  • pheromone - a secreted chemical in sweat or urine that causes specific physiological responses.
  • Whitten Effect - female mice either singly or housed together (in groups) can be induced into estrus by exposure to male mouse urine or their dirty bedding. The estrous cycle is applicable to many different species, not just the mouse reproductive cycle.

Spelling Note: When searching both American (estrous) and British (oestrous) spellings are used in the literature (More? American and British Spelling Variations). My thanks also to Prof Jill Becker for correcting an obvious spelling error on this page "The adjective is spelled with a 'u' after the o. 'Estrus' refers to the stage of the cycle and is the noun form of the word."

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Cite this page: Hill, M.A. (2018, March 19) Embryology Mouse Estrous Cycle. Retrieved from

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