One of the main aims of basic biological and medical research is to obtain an image as comprehensive as possible of the complex interactions that take place in the human body. This is essential to gaining an understanding of diseases and to the development of corresponding drugs and treatment methods. Although a large part of biomedical basic research involves animal-free testing methods, some questions can only be answered with the help of animal research. Alternative methods, such as computer models and cell cultures, can only reveal part of the overall picture. The reason for this is that cells in culture only express a small portion of all the features that cells in a whole tissue or an animal express. Thus, a cell in a dish would often not response in the same way as the same cell in a living animal.
Given the extensive biological similarity between humans and animals, laboratory animals offer the best possible alternative when it is not possible to study complex processes and interactions in the body directly on humans. All of the cells and organs, for example the heart, liver, kidneys, nerves and brain, fulfil the same tasks in two-legged and four-legged beings. Many diseases that pose a threat to humans also arise in the same or similar form in animals. Dogs get diabetes, some rats develop high blood pressure and mice and rats suffer from cancer and viral infections. Therefore, many questions can be answered with the help of tests in so-called "animal models". The differences between humans and animals are, of course, taken into account in the design of the tests – for example, in the dosage or way in which drugs are administered.
Moreover, such research often results in the discovery of treatments that can be used on both humans and animals. Almost 90 percent of all drugs used to treat humans and house pets are identical.