THE LABORATORY RAT


The laboratory rat was derived from the European brown rat, Rattus norvegicus, known commonly as the Norway rat.  R. norvegicus most likely had its origins in central Asia, and this adaptable species followed the migration of humans from this area to eventually colonize Europe and most of the world.  Rats were kept and bred as early as 1800 for the sport of terrier rat-baiting.  It is generally believed that albino animals were selectively removed from such groups of animals and were used for rat shows and to propagate additional albino animals.  During the 1800s, the albino Norway rat also found its way into the laboratory, and as such represents the first animal domesticated for scientific research.

The Wistar Institute in Philadelphia is the oldest independent research institute in the United States and was the site where rats became established as an important laboratory animal.  Henry Donaldson and his research staff worked to standardize the albino rat in order to undertake reproducible studies on the growth and development of the nervous system.  Their work provided the foundation for use of the rat in many disciplines, including nutrition, genetics, endocrinology, and biochemistry.  This endeavor was furthered by Helen King, who began work on inbred strains of rats around 1909.  The Wistar Institute supplied the “Wistar rat” to other laboratories until 1960, when breeding stocks and all rights were sold to a commercial company.

The Long-Evans strain (the hooded rat) originated at the University of California at Berkeley around 1920 through the collaborative efforts of Herbert Evans and Joseph Long as they studied reproductive physiology.  The Sprague-Dawley rat was bred through the efforts of Robert Dawley at the University of Wisconsin around 1925.

Like the mouse, the rat has many advantages as a research animal.  The laboratory rat is readily available, is inexpensive, and easy to house.  The genetic uniformity of available strains and stocks makes for reproducible research results.  These animals are intelligent, adaptable, and easy to handle.  The larger size of rats, compared to mice, makes them a more suitable surgical model.  Uses of the rat in research include, but are not limited to, studies of physiology, nephrology, endocrinology, nutrition, metabolism, drug evaluation and toxicology, and transplantable tumors.

Only the mouse is more widely used in research in terms of numbers of animals.  To give some idea of the importance of rodents in research, during 1998 17.2 million mice and 5.5 million rats were used at 1200 U.S. research institutions compared to a total of 1.2 million animals of other species.  Mice and rats together constitute approximately 90% of the total animals used for all research purposes.

Behavior

Housing

Diet and Nutrition

Animal Identification

Acclimatization

Special Anatomical and Physiological Features

Reproduction

Handling and Restraint

Injection Sites

Blood Collection

Miscellaneous Techniques

Recognition of Pain and Distress in Rats

Euthanasia

Occupational Health Concerns