How Has Science Advanced as a Result of Animal Experimentation?
Scientists use animals to do both basic and applied research. Applied research seeks to answer specific questions about a given disease or condition, usually in the context of a specific prevention therapy or treatment. Basic research seeks to build a base of knowledge about living organisms and how they function. Both forms of research are essential to continued medical progress.
Some people contend that scientists should use animals only for applied research, since that way the use of animals can be clearly associated with immediate benefits. But such a contention does not take into account the way scientific research works. Basic research provides the foundation on which applied research is built, and without the former the latter would cease.16 For example, research that examines the nerve cells responsible for vocalization in rhesus monkeys may seem far removed from any practical applications. But over 6 million people in the United States suffer from some kind of speech impairment, and without this fundamental research into speech mechanisms the hope for new treatments is slim.
It is difficult to predict which basic research will lead to eventual applications. But much of it eventually does, sometimes in areas far removed from the original research. All living things share certain characteristics, and basic research on one organism often produces knowledge that applies to many other organisms.
Both basic and applied research using animals are subject to a number of safeguards that make it very unlikely that the research will be unnecessary or poorly done. Before an experiment using a vertebrate animal is carried out, the protocol for that experiment must be reviewed by an institutional committee that includes a veterinarian and a member of the public, and during the research the animal's health and care are monitored regularly. Researchers need healthy animals for study in science and medicine, because unhealthy animals could lead to erroneous results. This is a powerful incentive for scientists to make certain that any animals they use are healthy and well-nourished. 17 Furthermore, research involving animals is expensive, and because funding is limited in science, only high-quality research is able to compete effectively for support.
Myasthenia gravis is a disease that causes excessive fatigue and muscle weakness, in some cases leading to death. The history of how researchers have come to understand the disease, which afflicts about 150,000 people in the United States, illustrates how a number of seemingly unrelated strands of biological knowledge can merge to form a significant advance.
An important part of the story begins with curare, a poison derived from plants, insects, and snake toxins that the Indians of Central and South America used on the tips of their arrows to immobilize and kill prey and enemies, in the nineteenth century, French researchers showed in frogs and other animals that curare blocks the transmission of signals from the nervous system to muscles. However, the transmission process itself was not well understood until the 1930s, when English researchers demonstrated in animals that nerves communicate with muscles by releasing a chemical, acetylcholine, that activates receptor molecules on the muscles. Curare somehow blocked the action of acetylcholine, paralyzing the muscle.
Next, two chemists from Taiwan isolated a powerful toxin from snake venom that paralyzed animals by blocking the receptors for acetylcholine. Other investigators used this toxin to obtain large quantities of the receptor from electric eels, which have many receptors in their electricity-generating organs. When researchers injected this receptor into rabbits, the rabbits developed a syndrome virtually identical to myasthenia gravis. The rabbits were making antibodies to the injected receptors, and these antibodies were attacking the rabbits' own receptors, causing the muscle weakness characteristic of the disease.
In this way, scientists came to realize that myasthenia gravis was an autoimmune disease, in which a person's own immune system attacks acetylcholine receptors on muscles. Treatments have been available for some time to lessen the effects of the disease—by improving the transmission of signals, for instance, or by suppressing the effects of the immune system. Further research, again being conducted in animals, is seeking a permanent cure by focusing on what causes the immune system to attack the body's own acetylcholine receptors.