Biomedical investigations still has predominant use of animal models, despite the availability of non-animal methods. The most commonly used animal model is the mouse.
The use of animals in physiological scientific investigations, also called vivisection, has been a very old practice. The first extensively documented practice of vivisection was done by Galen of Pergamum (130-200 A.D.) who performed dissections and vivisections on pigs, Barbary apes and dogs to study the physiology of the human body since dissection of the human corpse was prohibited by Roman laws (Nutton, 1973). Since then, the use of animals in medical research has yielded a lot of knowledge, both about the anatomy and physiology of the subject animals and the human body in virtually all areas of medical advances.
However, it should also be noted that there are non-animal methods of medical experimentation (clinical research using human cell lines, observation of patients and human autopsy), which have been noted to pave the way to the key discoveries in such areas as heart disease, cancer, immunology, anesthesia and psychiatry (Anderegg, 2006). It is also argued that experiments using animal models are sometimes misleading and just serve to delay medical advances.
Nevertheless, the use of animals in the laboratory is still a well established practice but has already evolved over the years as a result of changing perception on ethics, animal rights, and animal welfare. These developments are all reflected in the latest edition (7th ed.) of the Guide for the Care and Use of Laboratory Animals of the National Research Council (NRC) of the United States. The preface states that the Guide is intended to assist institutions in caring for and using animals in ways judged to be scientifically, technically, and humanely appropriate and also to assist individual investigators in fulfilling their obligation to plan and conduct animal experiments in accord with the highest scientific, humane, and ethical principles.
The most widely used animal models are mice. These are very common experimental animals in biology and psychology primarily because they are easier to handle and manipulate. Also, mice are mammals and thus share a high degree of homology with humans. However, not just any mouse can be used for research. The strains of mice used in biomedical research are genetically defined. A genetically defined strain is any strain in which the genetic background is known, is similar or identical from one mouse to another, and can be faithfully reproduced over time (Davisson, 1999). This has been accomplished with the use of inbred strains that can be repeatedly accessed as homogeneous experimental individuals, with predictable phenotypes and defined allelic composition.
The origin of mice inbreeding has been credited to the works of Clarence Cook Little (1888-1971) as a result of his works on cancer inheritance in mice. He developed the DBA (Dilute, Brown, Agouti) strain of inbred mice and he founded the Jackson Laboratory, which became the repository of strains of inbred mice (Russell, 1978). The laboratory has produced and/or housed the most common strains of inbred mice used nowadays in biomedical research: A, BALB/c, CBA, C57BL, C57BR, C57L, C58, DBA, N, and I. Over the years though, many substrains of inbred mice have been formed as a result of separation of a certain group from their parent colony (e.g. when housed in a separate laboratory) for more than 20 generations.
A general strain of mice that has been used extensively in medical research is the BALB/c strain. This is an inbred strain of mice from a stock that was obtained from H.J. Bagg of the Memorial Hospital in New York, which he obtained from a mouse dealer in Ohio in 1913 (Les, 1990). Later, this strain was moved to Jackson Laboratory, which now became the stock for all the BALB/c substrains used all over the world. This strain is used as a general-purpose strain in many different disciplines.
Because of the need of disease-specific models, strains of inbred mice have been mutated, knocked-out, or grafted with foreign genes to produce just about any human ailment. Strains of mice that succumb to Alzheimer’s disease, obesity, diabetes, cancer and countless other conditions are being used to study both the illnesses themselves and potential treatments. A recent example is the establishment of a transgenic mouse model forechovirus myocarditis and paralysis (Hughes et al., 2003).
References
Anderegg, C., K. Archibald, J. Bailey, M.J. Cohen, S.R. Kaufman, and J.J. Pippin. 2006. A critical look at animal experimentation. Medical Research Modernization Committee. Accessed on June 23, 2007 at http://www.mrmcmed.org/Critical_Look.pdf.
Davisson, M.T. 1999. Genetic and Phenotypic Definition of Laboratory Mice and Rats / What Constitutes an Acceptable Genetic-Phenotypic Definition. In: Microbial and Phenotypic Definition of Rats and Mice: Proceedings of the 1998 US/Japan Conference. International Committee of the Institute for Laboratory Animal Research
Hilgers J. and Arends J. W. A. 1985. A series of recombinant inbred strains between BALB/cHeA and STS/A strains. Curr. Top. Microbiol. Immunol. 122: 31-37.
Hughes, S.A., H.M. Thacker, and V.R. Racaniello. 2003. Transgenic mouse model for echovirus myocarditis and paralysis. PNAS 100(26):15906-15911
Institute of Laboratory Animal Resources, Commission on Life Sciences, National Research Council. 1996. Guide for the Care and Use of Laboratory Animals, 7th edition. Washington D.C.: National Academy Press.
Les, E.P. 1990. A Brief History of the Two Substrains of BALB/c, BALB/cJ, and BALB/cByJ Available from Animal Resources. JAX Notes Issue 443. Accessed on June 23, 2007 at http://jaxmice.jax.org/library/notes/443a.html
Nutton, Vivian. 1973. The Chronology of Galen's Early Career. Classical Quarterly 23:158-171.
