Target Discovery and Validation Reviews and Protocols

274 Iversen and Sørensen
the core of the body and the body surface. This regulation may affect the metabolic
rate of the animal and consequently result in different experimental results
compared with an animal in its thermoneutral zone. It is important that the environmental
temperature is precisely defined and kept within the defined range. The
temperature must be recorded and published. Environmental parameters are listed
in Appendix A in the Convention of the Council of Europe. Most rodents may be
kept at room temperatures between 20 and 24°C. It is important that the temperature
is kept constant, and it must be recorded and published.
2. Relative humidity should be kept in the range of 55±5%. Higher levels of relative
humidity may lead to disturbances in the metabolic rate, and excessively high
levels of relative humidity predispose for pathological conditions.
3. The light cycle has an important effect on the animal’s physiology and behavior.
Although most animals have their periods of highest activity during daylight
hours, the majority of laboratory animals are nocturnal and sleep during day. In
general 12 h of light and 12 h of dark is recommended for most laboratory animal
species. The light intensity must be adjusted to the need of the species and should
be constant in all parts of the room.
4. Exposure to chemicals may be a part of the procedure in an experiment or it may
be unintentional in the laboratory animal facility. The most important sources of
chemical contamination are animal excretions, bedding, cage or enclosure materials,
feed, and household chemicals.
5. We prefer to study male mice because these are generally larger than the females.
Size is a critical aspect because the induction of myocardial infarction requires
surgery on the coronary vessels of the small murine heart.
6. The ligature is tightened so the myocardial tissue is blanched on visual inspection.
7. The use of microtipped transducer catheters is preferable to avoid pressure artifacts.
8. Any weight should be adjusted for possible edema, e.g., by expressing the weight
relative to a bone length.
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