Mice and rats have played an essential role in scientific research throughout history. Indeed, many of the most important advances that have been made in the biological sciences have depended on rodents.
The historical background
Rodents have been used in scientific research since the mid-16th century in the study of basic physiological processes. From the 1850s, they began to be used more widely in laboratory studies and were sourced from British and American dealers who bred different coloured mice as pets. As rodents became increasingly important to medical research during the 20th century specific strains of rodents were bred so that scientists were able to distinguish between animals with different genes and characteristics. They were also bred to be more docile. Many different strains are now available to researchers and mice and rats have proved so useful that they are used in more than 95% of animal studies.
Why we use rodents
While there are obvious differences between the biology of rodents and humans, there is a great deal more similarity than meets the eye. Rodents are anatomically and physiologically very similar to humans so they are appropriate to use as a research tool. They also they share about 90% of the human genome. Almost all human genes that are linked to the development of disease have equivalent genes in rodents.
On a more practical level, scientists study rodents out of convenience. Rats and mice are cheap, easy to care for and don’t take up much space. They breed well in captivity all year round and have large litters. Due to their efficient reproduction and short lifespans of 2-3 years, it is possible to study several generations in a relatively short period of time. They also tolerate inbreeding better than many other mammalian species, which is important for two reasons:
- Firstly, it reduces genetic differences between rodents of the same strain so that the results of medical trials are more uniform and reliable.
- Secondly, it has enabled the development of genetically altered (‘transgenic’) rodents. They can be bred to carry genes that are similar to ones that cause human disease or genes can be made inactive (in ‘knockout’ animals) so researchers can address very specific scientific questions.
Rats vs mice
Mice have historically been more widely used and are normally preferred over rats for studies involving transgenic animals.
However, more research is beginning to be done on rats. They are larger than mice so handling them and performing procedures is much easier. Evidence suggests that rats are physiologically more similar to humans and experience diseases that more closely resemble ours. Finally, rats provide better opportunities for studying human psychology as they are better at learning and remembering new behaviours. They have even been trained how to ride skateboards!
Types of research
Rodents are used in a huge range of specialised fields such as neurology, toxicology, dentistry, immunology, oncology, psychology, genetics, nutrition, reproduction, surgery, physiology and pharmacology.
Rats and mice are used in the study of many human health problems such as hypertension, diabetes, obesity, epilepsy, respiratory disorders, asthma, deafness, Parkinson’s disease, Alzheimer’s disease, cancer, cystic fibrosis, HIV/AIDS, cardiovascular disease, muscular dystrophy and spinal cord injury.
Some rodents are bred to be susceptible to particular disorders – like hypertension or obesity. This has enabled researchers to directly study different health problems and to identify whether there are genetic links for particular diseases. Scientists rely on rodents when developing new drugs, treatments and therapies to improve human health.
Scientists are subject to strict protocols when working with animals and must be granted ethics approval before undertaking any research on mice or rats. They are required to adjust their experimental design to minimise the number of animals that need to be used. They also have to go through training on how to treat the animals with care in order to reduce any suffering or distress that they may go through.
Did you know?
There is no advantage for lab rats and mice to be white rather than their natural brown; they were simply bred to have white fur because scientists thought it looked cleaner!
Have you ever worked with mice or rats? Or maybe kept them as pets? Let me know in the comment section below.
Rick (2008). Lab mouse checkin’ out the camera [Image]. Retrieved from https://www.flickr.com/photos/rick-in-rio/2593063816
Hedrich, H. (Ed). (2004). The handbook of experimental animals: the laboratory mouse. London: Elsevier Academic Press.