Laboratory rats, or lab rats, is a term that refers to specific strains of domestic brown rats (fancy rats) who are bred and used for scientific research. While less commonly used for research than laboratory mice, rats have served as an important animal model for research in psychology and biomedical science. "Lab rat" is commonly used as an idiom for a test subject.
Origins of rat breeding
In 18th-century Europe, wild brown rats (Rattus norvegicus) ran rampant and this infestation fueled the industry of rat-catching. Rat-catchers would not only make money by trapping the rodents, but also by selling them for food or, more commonly, for rat-baiting. Rat-baiting was a popular sport, which involved filling a pit with rats and timing how long it took for a terrier to kill them all. Over time, breeding the rats for these contests may have produced color variations, notably the albino and hooded varieties. The first time one of these albino mutants was brought into a laboratory for a study was in 1828 for an experiment on fasting. Over the next 30 years, rats were used for several more experiments and eventually the laboratory rat became the first animal domesticated for purely scientific reasons.
In Japan, there was a widespread practice of keeping rats as a domesticated pet during the Edo period and in the 18th century guidebooks on keeping domestic rats were published by Youso Tamanokakehashi (1775) and Chingan Sodategusa (1787). Genetic analysis of 117 albino rat strains collected from all parts of the world carried out by a team led by Takashi Kuramoto at Kyoto University in 2012 showed that the albinos descended from hooded rats and all the albinos descended from a single ancestor. As there is evidence that the hooded rat was known as the "Japanese rat" in the early 20th century, Kuramoto concluded that one or more Japanese hooded rats might have been brought to Europe or the Americas and an albino rat that emerged as a product of the breeding of these hooded rats was the common ancestor of all the albino laboratory rats in use today. Domestic rats often differ from wild rats (various spp. of Rodentia) in several ways: they are calmer and significantly 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.
Use in research
Research labs in the late 19th and early 20th centuries used rats to study nutrition, genetics, psychology, reproduction, and cancer. Over the years, rats have been used in many experimental studies that have advanced human health and wellbeing.
The historical importance of this species to scientific research is reflected by the amount of literature on it: roughly 50% more than that on laboratory mice. Laboratory rats are frequently subject to dissection or microdialysis to study internal effects on organs and the brain, such as for cancer or pharmacological research. After studies end, laboratory rats may be euthanized or, rarely, become pets. During food rationing due to World War II, British biologists had eaten laboratory rats, creamed.
Nutrition In 1895, Clark University in Worcester, Massachusetts, established a population of domestic albino brown rats to study the effects of diet and for other physiological studies. The first rat colony in America used for nutrition research was started in January 1908 by Elmer McCollum and then, nutritive requirements of rats were used by Thomas Burr Osborne and Lafayette Mendel to determine the details of protein nutrition.
Genetics The genetics of rats was studied by William Ernest Castle at the Bussey Institute of Harvard University until it closed in 1936. Much of the genome of Rattus norvegicus has been sequenced. In October 2003, researchers succeeded in cloning two laboratory rats by nuclear transfer. This was the first in a series of developments that have begun to make rats tractable as genetic research subjects, although they still lag behind mice, which lend themselves better to the embryonic stem cell techniques typically used for genetic manipulation. Many investigators who wish to trace observations on behavior and physiology to underlying genes regard aspects of these in rats as more relevant to humans and easier to observe than in mice, giving impetus to the development of genetic research techniques applicable to rats.
Psychology W. S. Small suggested that rats could measure the rate of learning in a maze; a suggestion employed by John B. Watson for his Ph.D. dissertation in 1903.
Laboratory rats have also proved valuable in psychological studies of learning and other mental processes, as well as to understand group behavior and overcrowding (with the work of John B. Calhoun on behavioral sink). A 2007 study found rats to possess metacognition, a mental ability previously only documented in humans and some primates.
Reproduction The reproductive function of rats was studied at the Institute for Experimental Biology at the University of California, Berkeley by Herbert McLean Evans and Joseph A. Long.
Neoplasms Rats have long been used in cancer research; for instance, at the Crocker Institute for Cancer Research. A 1972 study compared neoplasms in Sprague Dawleys from six different commercial suppliers and found highly significant differences in the incidences of endocrine and mammary tumors. There were even significant variations in the incidences of adrenal medulla tumors among rats from the same source raised in different laboratories. All but one of the testicular tumors occurred in the rats from a single supplier. The researchers found that the incidence of tumors in Sprague Dawleys from different suppliers varied as much from each other as from the other strains of rats. The authors of the study "stressed the need for extreme caution in evaluation of carcinogenicity studies conducted at different laboratories and/or on rats from different sources."
… excerpt ends here. Continue reading the full article.
