The Natural History of Model Organisms: The Norway rat, from an obnoxious pest to a laboratory pet

  1. Klaudia Modlinska  Is a corresponding author
  2. Wojciech Pisula
  1. Polish Academy of Sciences, Poland
1 figure and 1 table


A laboratory-bred wild rat.

R. norvegicus is a relatively small rodent with a brown fur and sparsely haired tail. Its head is stout with a pointed muzzle and darkly pigmented, slightly bulging eyes. Characteristic of all rodents, rats have large and continuously growing front teeth. The durable enamel on the front surface of these teeth contains an iron-based pigment, which gives them an orange color. This individual belongs to the Warsaw Wild Captive Pisula Stryjeck (WWCPS) colony in Poland. 

Image credit: Klaudia Modlinska and Rafał Stryjek.


Table 1
The most common stocks and strains of the laboratory rat.
Coat colorOrigineUse and characteristics
WistaroutbredalbinoThe Wistar Institute, Philadelphia, Pennsylvania, USA (1906)The most-popular general multi-purpose models. Studies of infectious diseases, aging and as a surgical model.
Wistar HanoutbredalbinoZentralinstitute für Versuchstierzucht, Hannover, GermanyA general multi-purpose model, popular in preclinical safety assessments, and as an aging, oncological and surgical model.
Wistar Kyotooutbredalbinothe Kyoto School of Medicine, JapanNormotensive controls for the spontaneous hypertensive line, a depression and autism model.
Sprague DawleyoutbredalbinoThe Sprague-Dawley farms, Madison, Wisconsin, USA (1925). Derived from a hybrid Hooded male and a female Wistar.Behavioral studies and as models in obesity, oncology and surgical research.
Long EvansoutbredhoodedThe University of California, USA. Created by Herbert McClean Evans and Joseph Abraham Long (1915–1922). A result of crossbreeding albino females and wild males caught near the University.Behavioral studies. Known for their docility and ease of breeding but prone to spontaneous seizures.
Brown NorwayinbredpigmentedDerived from a pen-bred colony of wild-caught rats maintained by King and Aptekman at the Wistar Institute in the 1930s. The strain was created by Silvers and Billingham in 1958 (Hedrich, 2000).Immunological and transplantation studies. Selected as the sequencing target in Gibbs et al. (2004).
LewisinbredalbinoDeveloped by Margaret Lewis from the Wistar rats in the early 1950sEnhanced susceptibility to many experimental inflammatory conditions, such as PGPS-induced arthritis, adjuvant-induced arthritis, collagen-induced arthritis, autoimmune encephalitis, autoimmune thyroiditis and enterocolitis (Zhang, 2010). Characterized by their docile behavior but relatively low fertility.
Zucker fatty ratsoutbredhoodedDeveloped by crossing the Sherman strain with the Meck stock 13M strain (Kava et al., 1990)Most often used as a model of genetic obesity. Relatively insensitive to leptin due to a mutation in the long form of the leptin receptor (van der Spek et al., 2012). Characterized by hyperlipidemia, hypercholesterolemia and hyperinsulinemia (Kava et al., 1990).
Nude ratsinbredalbino hooded greyThe nude mutation first encountered in 1953 in an outbred colony of hooded rats at the Rowett Research Institute in Aberdeen, Scotland. The mutation reappeared independently in Aberdeen in 1977 and in New Zealand in 1979 (Hanes, 2006). Since than numerous new strains have been developed. For instance, a spontaneous mutation model isolated from a Crl:CD(SD) colony in Charles River in the late 1980s.Characterized by almost complete absence of fur. Experimental models for a variety of immunological, surgical, infectious, transplant-related and oncological procedures. Uniquely capable of maintaining increased tumours without visible distress and enlarged body weight (Hanes, 2006). Also useful in wound healing and dermatology.
  1. *Inbred rat strains are created by brother-sister or parent-offspring mating for at least 20 generations. It produces almost genetically identical individuals (after 20 generations rats are homozygous at 98.7% of all alleles and the residual heterozygosity decreases as inbreeding continue; Lohmiller and Swing, 2006). Outbred rat stocks are developed from large colonies with males and females selected randomly from different breeding groups; stock animals are genetically different, which can represent inter-individual differences occurring in natural environment (Lohmiller and Swing, 2006; Olson and Graham, 2014).

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  1. Klaudia Modlinska
  2. Wojciech Pisula
The Natural History of Model Organisms: The Norway rat, from an obnoxious pest to a laboratory pet
eLife 9:e50651.