FIGURE 4-2 UK Home Office–tracked animal procedure data, 1988 and 2009. NHP = non-human primate.
SOURCE: Yates presentation citing UK Home Office Web site.
as chronic recording techniques enables the study of a single animal over a prolonged period of time, leading to greater data collection from single animals. This results in fewer animals needed per study. Thus, the use of non-human primates, which can be trained for more elaborate tasks than cats, has become more economically feasible. Refinement, Yates pointed out, does not always lead to use of a lower species.
Transgenic Mouse Models
The most significant contributor to the increased use of rodents in biomedical research has been the development of transgenic mouse models. In the late 1980s, Capecchi, Evans, and Smithies developed principles for introducing specific gene modifications in mice by the use of embryonic stem cells leading to the development of the first knockout mouse. Today, human genes can be inserted into a mouse or overexpress a particular gene.