Rat Development

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The rat (taxon - rattus) is readily available as inbred, outbred and mutant strains. They have been generally beaten as a model by their rodent mice brethren, as the molecular tools that became available (stem cells, knockout genes, etc).

Rat embryos do have the advantage of being much larger than mouse embryos and easy to breed. Another advantage of rats is in vision development studies, as that retinal development continues postnatally (most vertebrate neurological systems are difficult to access during periods of development). Rat development is also generally 1 day behind that of mouse. (The table below gives details relating to the staging of rat development). Below this are a list of internet resources relating to the rat.

Rat Links: rat | Rat Stages | Rat Timeline | Category:Rat
Historic Embryology - Rat 
1951 Albino Rat Development | 1921 Somitogenesis | 1933 Vaginal smear | 1938 Heart

Some Recent Findings

  • Cross-Species Genome Wide Expression Analysis during Pluripotent Cell Determination in Mouse and Rat Preimplantation Embryos[1] "The transition between morula and blastocyst stage during preimplantation development represents the first differentiation event of embryogenesis. Morula cells undergo the first cellular specialization and produce two well-defined populations of cells, the trophoblast and the inner cell mass (ICM). ... This is the first study investigating the gene expression changes during the transition from morula to blastocyst in the rat preimplantation development. Our data show that in the pluripotent pool of cells of the rat and mouse preimplantation embryo substantial differential regulation of genes is present, which might explain the difficulties observed for the derivation and culture of rat ESCs using mouse conditions."
  • Generation of germline-competent rat induced pluripotent stem cells[2] "Our data clearly demonstrate that using only three reprogramming factors (Oct3/4, Klf4, and Sox2) rat somatic cells can be reprogrammed into a ground state. Our generated riPSCs exhibited germline transmission in either rat-rat intraspecific or mouse-rat interspecific chimeras."
  • Comparison of staging systems for the gastrulation and early neurulation period in rodents[3]"Because there is no standard developmental staging system for the early postimplantation period of rodent embryos, investigators must now choose between a variety of systems that differ significantly. We have reviewed many of these staging systems and have summarized the ambiguities within them and the inconsistencies among them. In order to compare systems, we first obtained a consensus of the order of developmental events from the literature, and then attempted to fit existing systems into this order taking into account inconsistencies in terminology and blurred borderlines between stages."
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.

Links: References | Discussion Page | Pubmed Most Recent | Journal Searches

Search term: Rat Embryology

Svenja Rink, Dominik Arnold, Aliona Wöhler, Habib Bendella, Carolin Meyer, Marilena Manthou, Theodora Papamitsou, Levent Sarikcioglu, Doychin N Angelov Recovery after spinal cord injury by modulation of the proteoglycan receptor PTPσ. Exp. Neurol.: 2018; PubMed 30118740

Anica M Petkovic, Vladimir Lj Jakovljevic, Jovana V Bradic, Jovana N Jeremic, Nevena S Jeremic, Tamara R Nikolic Turnic, Nemanja U Jovicic, Vesna Z Rosic, Ivan M Srejovic, Vladimir I Zivkovic The Effects of Potassium Cyanide on the Functional Recovery of Isolated Rat Hearts after Ischemia and Reperfusion: The Role of Oxidative Stress. Oxid Med Cell Longev: 2018, 2018;5979721 PubMed 30116485

Neval Yaman Görük, Engin Deveci Immunoexpression of vascular endothelial growth factor and B-cell lymphoma 2 in the uterine tissue of rats treated with melatonin in the estrus phase1. Acta Cir Bras: 2018, 33(7);629-640 PubMed 30110064

Tuğba Özaydın, Yasemin Öznurlu, Emrah Sur, İlhami Çelik, Deniz Uluışık ##Title## Acta Histochem.: 2018; PubMed 30107890

Nesrin Abd Allah Fath Allah Salman, Fatma El-Nabawia Abdel-Hady El-Safty, Mostafa Mahmoud El-Habeby, Wael Badr El-Kholy, Gehan Farouk Ali El-Akabawy Vitamin C attenuats the toxic effect of nutmeg on primary visual occipital cortex in rats. Folia Morphol. (Warsz): 2018; PubMed 30106466

Rat Estrous Cycle

Left oviduct of rat
Left oviduct of rat

See the review of the rat estrous cycle.[4] One of the best characterised polyestrous reproductive cycles, though different species of rats may differ in reproduction. In general, puberty occurs at 6-8 weeks when the estrous cycle commences each cycle is 4-5 days. The estrous cycle is polyestrous, more than one estrous cycle during a specific yearly time, with an estrous period of approximately 12 hours.

Links: estrous cycle | PubMed Search - rat estrous cycle

Species Stages Comparison

The table below gives an approximate comparison of human, mouse and rat embryos based upon Carnegie staging.

Species Embryonic Comparison Timeline
Carnegie 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 E4.5 E5.0 E6.0 E7.0 E8.0 E9.0 E9.5 E10 E10.5 E11 E11.5 E12 E12.5 E13 E13.5 E14 E14.5 E15 E15.5 E16
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
Table References  

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
Otis EM and Brent R. Equivalent ages in mouse and human embryos. (1954) Anat Rec. 120(1):33-63. PMID 13207763

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

Witschi E. Rat Development. In: Growth Including Reproduction and Morphological Development. (1962) Altman PL. and Dittmer DS. 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.

Animal Model Comparison
Postnatal Animal Models mouse rat pig
Pregnancy period (days) 18 – 21 21 – 23 110 – 118
Placenta type Discoidal, decidual
hemoendothelial choroidea
Discoidal, decidual
hemoendothelial choroidea
Litter size 6 – 12 6 – 15 11 – 16
Birth weight (g) 0.5 – 1.5 3 – 5 900 – 1600
Weaning weight male/female (g) 18 – 25/16 – 25 55 – 90/45 – 80 6000 – 8000
Suckling period (days) 21–28 21 28–49
Solid diet beginning (days) 10 12 12 – 15
Puberty male/female (week) 4 – 6/5 6/6 – 8 20 – 28
Life expectancy (years) 1 - 2 2 - 3 14 – 18
Table data - Otis and Brent (1954)[5]   Links: timeline

Rat oocyte 01.jpg

Rat oocytes showing metaphase plate[6]

Links: Rat Timeline

Placenta Development

For review of the rat placenta.[7]

Adrenal and Gonad Development

Adrenal and gonad steroidogenic factor 1 expression.jpg

Adrenal and gonad steroidogenic factor 1 expression[8]


  1. Casanova EA, Okoniewski MJ & Cinelli P. (2012). Cross-species genome wide expression analysis during pluripotent cell determination in mouse and rat preimplantation embryos. PLoS ONE , 7, e47107. PMID: 23077551 DOI.
  2. Hamanaka S, Yamaguchi T, Kobayashi T, Kato-Itoh M, Yamazaki S, Sato H, Umino A, Wakiyama Y, Arai M, Sanbo M, Hirabayashi M & Nakauchi H. (2011). Generation of germline-competent rat induced pluripotent stem cells. PLoS ONE , 6, e22008. PMID: 21789202 DOI.
  3. Fujinaga M, Brown NA & Baden JM. (1992). Comparison of staging systems for the gastrulation and early neurulation period in rodents: a proposed new system. Teratology , 46, 183-90. PMID: 1440421 DOI.
  4. Hubscher CH, Brooks DL & Johnson JR. (2005). A quantitative method for assessing stages of the rat estrous cycle. Biotech Histochem , 80, 79-87. PMID: 16195173 DOI.
  5. Otis EM and Brent R. Equivalent ages in mouse and human embryos. (1954) Anat Rec. 120(1):33-63. PMID 13207763
  6. Webb RL, Findlay KA, Green MA, Beckett TL & Murphy MP. (2010). Efficient activation of reconstructed rat embryos by cyclin-dependent kinase inhibitors. PLoS ONE , 5, e9799. PMID: 20333307 DOI.
  7. Furukawa S, Hayashi S, Usuda K, Abe M, Hagio S & Ogawa I. (2011). Toxicological pathology in the rat placenta. J Toxicol Pathol , 24, 95-111. PMID: 22272049 DOI.
  8. Val P, Lefrançois-Martinez AM, Veyssière G & Martinez A. (2003). SF-1 a key player in the development and differentiation of steroidogenic tissues. Nucl. Recept. , 1, 8. PMID: 14594453 DOI.



Kito S, Yano H, Ohta Y & Tsukamoto S. (2010). Superovulatory response, oocyte spontaneous activation, and embryo development in WMN/Nrs inbred rats. Exp. Anim. , 59, 35-45. PMID: 20224168

Sheng Y, Lin CC, Yue J, Sukhwani M, Shuttleworth JJ, Chu T & Orwig KE. (2010). Generation and characterization of a Tet-On (rtTA-M2) transgenic rat. BMC Dev. Biol. , 10, 17. PMID: 20158911 DOI.

Ahmed RP, Haider KH, Shujia J, Afzal MR & Ashraf M. (2010). Sonic Hedgehog gene delivery to the rodent heart promotes angiogenesis via iNOS/netrin-1/PKC pathway. PLoS ONE , 5, e8576. PMID: 20052412 DOI.

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Search Pubmed: Rat Development

Additional Images

Historic Images

Links: Bailey, F.R. and Miller, A.M. (1921)

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

  • Rat Genome Database RGD

Simon N Twigger, Mary Shimoyama, Susan Bromberg, Anne E Kwitek, Howard J Jacob, RGD Team The Rat Genome Database, update 2007--easing the path from disease to data and back again. Nucleic Acids Res.: 2007, 35(Database issue);D658-62 PubMed 17151068

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Cite this page: Hill, M.A. (2018, August 21) Embryology Rat Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Rat_Development

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© Dr Mark Hill 2018, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G