Appropriate animals may include mice, rats, guinea pigs, rabbits, cats, dogs, etc. Characteristics of the animals such as strain, sex, age and holding conditions should be specified.
Disease models can be made by treating animals with certain chemicals or other modalities. For example, immunologically depressed mice can be made by treating them with an immunosuppressive agent, such as cyclophosphamide. Such animals can be used to evaluate immunostimulating activity of a test medicine.
Animals with genetic defects can also be useful: for example the autoimmune mouse (NZB W/F1, MRL/1) and the hypertensive rat (SHR), etc. For study of those herbal medicines which are used under the principles of traditional medicine, animal models may need to be established according to those principles.
Test assays can use
• whole animals;
• isolated organs and tissues;
• blood and its components;
• ex vivo and tissue culture cells; and
• subcellular constituents.
Careful attention must be given to the selection of the test system since in vitro assays, although less expensive, may not provide such factors as metabolic activation which may be necessary for the biological activity of a herbal medicine. On the other hand, body fluids from test animals may contain such biologically active metabolites and be used successfully in less complex test systems.
Special attention should be given to the sensitivity, reproducibility and general acceptance of the test animals or test systems selected.
An examination of the literature may help to select the species and test systems considered to be most predictive of clinical results and therefore provide the most useful information.