Laboratory Rats

Animal models in Bio-Medical Research

Animal models have been used in biomedical research since the beginning of scientific investigations. They contribute to our understanding of physiology, disease, behavior and mapping the genome. Rats have been a favorite laboratory animal because they are readily available, inexpensive, easy to house and breed, and easy to handle. Laboratory rats are brown rats (Rattus norvegicus) bred specifically for performing scientific research. They have been used as animal models in many fields of research including medicine, psychology, environmental science, and toxicology, since the mid-19th century.

Breeding of Rats by Rat Baiters

Although Laboratory rats are physiologically and psychologically different from their wild relatives, they are not a different species. To understand where they come from we must go back in history to the 1800’s when records first appear about the sport of Rat-Baiting. This blood sport provided entertainment and gambling opportunities by placing rats in a pit and allowing people to place bets on how long it takes for a dog, often a terrier, to kill them. Over time brown rats were bred specifically for rat-baiting. It is generally thought that albino rats were selectively removed from breeding groups for use in rat shows and to propagate more albino rats. Since these rats were smaller than feral rats, relatively docile (making them easy to handle), can tolerate overcrowding in cages without fighting, and are prolific breeders, they were favored by rat baiters and were enjoyed by people who were beginning to keep pet rats as a hobby.

Rat Facts – Did You Know

Some scholars have speculated that lab and fancy rats are related to the wild brown rat (Rattus novegicus) through Queen Victoria’s rat catcher, Jack Black. He caught and ridded the royal court of rats, and kept interesting rats for himself. He sold “fancy rats” to rat baiters and to people interested in the new fad of keeping rats as pets. Jack Black also bred a strain of albino rats that he sold to French scientists. The progenitor of today’s laboratory rats, the Wistar rat, from the Wistar Institute in Philadelphia, was started from these albino rats supplied from France. [Sullivan]

Strains of Rats and Morphology

A strain of rats is a group of rats that are inbred from brothers and sisters, thus sharing a common ancestry. All the rats in a strain are all morphologically similar (they look alike) and are almost clones of each other. Strains of rats are favored in research since the effects of research are likely to be the result of the study and not because of the individuality of a single rat.

Rats Preferred to Mice in Laboratory Research

Although mice too are frequently used as laboratory animals, rats are frequently the preferred choice by researchers. Even though rats look outwardly similar to mice, their evolutionary differences have been compared by anatomists as being as different as old-world monkeys are to humans. Rats are larger with a more human-like physiology. Their large size makes it easier to study their anatomy and physiology and to operate on cancerous tumors. Their circulatory system is similar to humans, allowing for hypertension and arterial scleroses studies. They metabolize drugs more like humans and are far more intelligent than mice, making them more likely to display behaviors like Parkinson’s, Alzheimer’s, schizophrenia, and autism. And recently, researchers developed techniques to modify a rat’s genetic makeup, allowing researchers to design rats that better model human disease.

Some History on Rats as an Animal Model

Rats first become an important animal model for research around 1906. Henry Donaldson, of Philadelphia’s Wistar Institute, obtained albino rats from a lab in France and standardized them to produce an animal model to study the nervous system. Wistar Rats were very successful and the Wistar Institute continued supplying “Wistar Rats” to other labs until the rights were sold to a commercial supplier in 1960. Other rat strains were developed from albino brown rats. Herbert Evans and Joseph long developed the Long-Evans strain around 1920 at the University of California at Berkley. The strain was favored for studying reproductive physiology. The Sprague-Daelwy strain, a multi-purpose rat for medical research, known for its calm nature, was bred at the University of Wisconsin around 1925.

Albinism in Rats

Over time albinism became a useful genetic marker to identify a healthy, docile, and physically stable strain of rats. Using a genetic marker, like albinism helps researchers identify variations within a strain. This way when research is performed on a Wistar Rat, we know the side effects are due to the drug, not because of individual variations within each rat.

Hooded Rat

Albino rats, of course, are not the only rat used in research. The hooded rat is a long established stable strain. The black coloration on the rats head and shoulder is the genetic marker to help identify this rat.

Ethical Concerns About Using Lab Rats

People have developed ethical concerns over the years about using animals in research and medical education. This has been especially true in toxicology and bio-medical research, though concerns are articulated about less invasive research such as behavioral studies. Although extreme views are held by small minorities, the general view is that research animals will be treated humanely. Research and educational institutes are now often required to justify the use of animals in their programs.

Legislation for the Humane Treatment of Research Animals

Legislation in many countries regulates the humane treatment for research animals. It is expected that animals will be maintained in clean, uncrowded housing, adequately fed, and maintained in good health. Many recognize that it is difficult to establish guidelines for maintaining an animal’s psychological health. There are many strategies to maintain the ethical treatment. On is the application of the “Three Rs of ethical treatment of lab animals”. They are…

• Replacement, which refers to using less sentient species rather than more sentient species, or that animals should not be used at all if there is a “no-animal” alternative for research or educational use.
• Reduction, which refers to reducing the number of animals to only the minimum necessary amount to achieve the goal of a research or education.
• Refinement, which refers reducing the pain or suffering imposed on every animal used in research or education. It does not differentiate between the pains and suffering between animals, so one species would not be substituted for another.

Examples of Rat Strains

Here are a few popular and unusual laboratory rat strains: Wistar Rat, an Albino Rat used for general research. Long-Evans Rat (Hooded Rat), multipurpose, favored in behavioral and obesity research. Also a favorite fancy rat pet. Sprague-Dawley, an unusually docile albino rat with a low incidence of spontaneous tumors. Zucker Rat Strain, bred to be prone to diabetes and obesity are favored for weight and hypertension research. Hairless rat, favored for immune system and genetic kidney disease research. This guy is growing a human ear on an artificial frame under it’s skin. Shaking rat Kawaski, mutant Wistar strain (also an albino) that is predisposed to neurological abnormality. Spontaneous Dwarf Rat (SDR) next to a normal sized rat. The SDR has a mutation in growth hormone. Favored for some cancer studies. Knockout Rats (KO), are very recent innovations in rat husbandry. There are many KO strains. KO rats have a selected gene turned off through targeted mutation. Green fluorescent protein (GFP) transgenic rat (in cage with albino rat for comparison), used in transplant research. See this amazing video on the discovery of a closeness between rat hair cells and brain stem cells. Listen to what flashes in the mind of a scientist when he sees this creature light up!

Evolving Rats – Observing Rats in the Natural Environment

This documentary film shows released, domesticated rats of different strains, are compared and contrasted with feral rats in a controlled, yet natural environment. See how they hunt, nest and compete for resources and survival. Call today at 1-800-986-1006 for a free rodent inspection. You’re also welcome to complete the form below and a caring Hearts Pest Management representative will contact you shortly.

References on “Lab Rats”

Please click on the links below for more information on Laboratory rats. And look for the RatsMania article on keeping pet rats. This author wants a pet green fluorescent protein transgenic rat for a nightlight.

Bibliography on Lab Rats

Ethical Treatment of Animals in Applied Animal Behavior Research. The International Society for Applied Ethology. Web. 2014. < http://www.applied-ethology.org/ethical_guidelines.html> Hakamata, et el. Green fluorescent protein-transgenic rat: a tool for organ transplant research. Biochemistry and Biophysical Research Communications. Aug. 31, 2001; 286(4): 779-785. Laboratory rat. Wikipedia. Web. January 14, 2014. http://en.wikipedia.org/wiki/Laboratory_rat> Rat Species, Strains, Breeds, and Varieties. Rat Systematics. Anne’s Rat Page. Web. ND. < labome.com/> Rat. Wikipedia. Web. January 6, 2014. < http://en.wikipedia.org/wiki/Rat> Robert Sullivan. Rats; observations on the Histories and Habitat of the Cities Most unwanted inhabitants. Bloomsbury. Book. Pg. 6. 2002. The Laboratory Rat. Institutional Animal Care & Use Committee. Web. ND. <http://www.lssu.edu/faculty/jroese/AnimalCare/laboratory%20rats.htm> Three R’s Alternative. Canadian Council on Animal Care in Science. CCAC. Web. ND. http://www.ccac.ca/en_/threer