The influence of the cage environment on rodent physiology and behavior: Implications for reproducibility of pre-clinical rodent research

- A clearly defined stable environment is essential to generating consistent experimental outcomes.
- The purpose of this article is to help investigators gain a better understanding of how even seemingly minor environmental changes on the animals and the data.
- The cage environment is highly complex; the perceptions and experiences of cage occupants may not conform to human assumptions.
- A complete and detailed description of the animal environment is a vital part of any research methods section.

The reproducibility of pre-clinical research is an important concern that is now being voiced by constituencies that include the National Institutes of Health, the pharmaceutical industry, Congress, the public and the scientific community. An important facet of performing and publishing well-controlled reproducible pre-clinical research is to stabilize and more completely define the environment of the animal subjects. Scientists who use rodents in research generally recognize the importance of maintaining a stable animal environment. However, despite a theoretical and general awareness of these issues, many may lack a true appreciation of how significantly even seemingly minor variations in the environment can affect research outcomes. The purpose of this article is to help investigators gain a more comprehensive and substantiated understanding of the potentially significant impact of even seemingly minor environmental changes on the animals and the data. An important caveat to this article is that the examples presented were selected from a very large literature, admittedly in order to illustrate certain points. The goal of this article is not to provide an overview of the entire literature on how the environment affects rodents but rather to make preclinical scientists more aware of how these factors can potentially influence the experimental data and contribute to poor reproducibility of research.