Laboratory rat

A laboratory rat is a rat of the species "Rattus norvegicus" which is bred and kept for scientific research. Laboratory rats have served as an important animal model in research in psychology, medicine, and other fields.

History

In 1895, a population of domesticated, white "Rattus norvegicus" rats was established at Clark University for research on diet and physiology. Over the years, rats have been used in many experimental studies, which have added to our understanding of genetics, diseases, the effects of drugs, and other topics in health and medicine. Laboratory rats have also proved valuable in psychological studies of learning and other mental processes.

Domestic rats differ from wild rats in many ways. They are calmer and less likely to bite, they can tolerate greater crowding, they breed earlier and produce more offspring, and their brains, livers, kidneys, adrenal glands, and hearts are smaller.

Scientists have bred many strains or "lines" of rats specifically for experimentation. Most are derived from the albino Wistar rat, which is still widely used. Other popular strains are the Sprague Dawley, Fischer 344, [cite web | url = http://www.afip.org/vetpath/POLA/POLA96/oldrats.txt | title = 43rd Annual Pathology of Laboratory Animals Course] , Holtzman albino strains, the Long-Evans, and Lister black hooded rats. Inbred strains are also available but are not as commonly used as inbred mice.

Rat strains are generally not transgenic, or genetically modified, because the easy techniques of genetic transformation that work in mice do not work for rats. This has disadvantaged many investigators, who regard many aspects of behavior and physiology in rats as more relevant to humans and easier to observe than in mice and who wish to trace their observations to underlying genes. As a result, many have been forced to study questions in mice that might be better pursued in rats. In October 2003, however, researchers succeeded in cloning two laboratory rats by the problematic technique of nuclear transfer. So rats may begin to see more use as genetic research subjects. Much of the genome of "Rattus norvegicus" has been sequenced. [cite web | url = http://www.ensembl.org/Rattus_norvegicus/index.html | title = Genome project | accessdate = 2007-02-17 | last = | first = | date = |work = www.ensemble.org | quote = ]

Wistar rat

"Wistar rats" are an outbred strain of albino rats belonging to the species "Rattus norvegicus". This strain was developed at the Wistar Institute for use in biological and medical research, and is notably the first rat strain developed to serve as a model organism at a time when laboratories primarily used "Mus musculus", or the common House mouse. Most laboratory rat strains are descended from a colony of rats established at the Wistar Institute in 1906 by American physiologist Henry Donaldson, scientific administrator Milton J. Greenman, and genetic researcher/embryologist Helen Dean King. [* [http://www.amphilsoc.org/library/mendel/1998.htm Clause, B. T. (1998). The Wistar Institute Archives: Rats (Not Mice) and History, "Mendel Newsletter" February, 1998.] ]

The Wistar rat is currently one of the most popular rat strains used for laboratory research. It is characterized by its wide head, long ears, and having a tail length that is always less than its body length. The Sprague Dawley rat and Long-Evans rat strains were developed from Wistar rats.

Sprague Dawley rat

The "Sprague Dawley rat" is an outbred multipurpose breed of albino rat used extensively in medical research. [cite journal
author=Drachman RH, Root RK, Wood WB Jr.
title=Studies on the effect of experimental nonketotic diabetic mellitus on antibacterial defense
journal=J Exp Med
year=1966
volume=124
pages=227–40
doi=10.1084/jem.124.2.227] [cite journal
author=Hsu CC, Lai SC
title=Matrix metalloproteinase-2, -9 and -13 are involved in fibronectin degradation of rat lung granulomatous fibrosis caused by "Angiostrongylus cantonensis"
journal=Int J Exp Pathol
year=2007
volume=88
pages=437–43
pmid=18039280
doi=10.1111/j.1365-2613.2007.00554.x] [cite journal
author=Horiuchi N, Suda T, Sasaki S, Takahashi H, Shimazawa E, Ogata E.
title=Absence of regulatory effects of 1alpha25-dihydroxyvitamin D3 on 25-hydroxyvitamin D metabolism in rats constantly infused with parathyroid hormone
journal=Biochem Biophys Res Commun
year=1976
volume=73
pages=869–75
pmid=15625855
doi=10.1016/0006-291X(76)90202-3] [cite journal
author=Sukov W, Barth DS
title=Three-dimensional analysis of spontaneous and thalamically evoked gamma oscillations in auditory cortex
journal=J Neurophysiol
year=1998
volume=79
pages=2875–84
pmid=9636093] Its main advantage is its calmness and ease of handling. [cite web|title="Online Medical Dictionary"|url=http://cancerweb.ncl.ac.uk/cgi-bin/omd?rats,+sprague-dawley|date=1998-12-12|accessdate=2007-12-15] This breed of rat was first produced by the Sprague Dawley farms in Madison, Wisconsin (later to become the Sprague Dawley Animal Company). The breeding facilities were purchased first by Gibco and then by Harlan (now Harlan Sprague Dawley) in January 1980. [cite web|title=Harlan Sprague Dawley|url=http://www.harlan.com/models/spraguedawley.asp|accessdate=2007-12-15]

Sprague Dawley rats possess several interesting anatomical features. Because the esophagus enters the stomach at the lesser curvature through a fold of tissue of the stomach, these rats are unable to vomit. They have no gall bladder. The left lung has only one lobe, while the right has four. During periods of stress, they produce dark tears, which contain a pigment which is fluorescent under UV light. [cite web|title=Ace Animals, Inc.|url=http://www.aceanimals.com/SpragueDawley.htm|accessdate=2008-10-06]

The average litter size of the Sprague Dawley rat is 10.5. The adult body weight is 250-300g for females, and 450-520g for males. The typical life span is 2.5 - 3.5 years. [ [http://aceanimals.com/SpragueDawley.htm Ace Animals website] Retrieved on 2008-3-15.]

Long-Evans rat

"Long-Evans rats" are an outbred strain of rats belonging to the species "Rattus norvegicus". This strain was developed by Drs. Long and Evans in 1915 by crossing several Wistar females with a wild gray male. Long Evans rats are white with a black hood, or occasionally white with a brown hood. They are utilized as a multipurpose model organism, frequently in behavioral and obesity research.

Zucker rat

"Zucker rats" were bred to be a genetic model for research on obesity and hypertension. They are named after Lois M. Zucker and Theodore F. Zucker, pioneer researchers in the study of the genetics of obesity. Zucker rats are also known as Zucker Fatty rats for their tendency toward obesity.

See also

*Morris water maze
*Rat genome database

References

External links

* [http://www.nature.com/nature/focus/ratgenome/ Nature: Rat Genome]
* [http://rgd.mcw.edu/ Rat Genome Database]
* [http://www.criver.com/research_models_and_services/research_models/Long_Evans.html Charles River Laboratories]
* [http://www.harlan.com/models/longevans.asp Harlan Sprague Dawley]