The between-laboratory effects on behavioral phenotypes and spatial learning performance of three strains of laboratory mice known for divergent behavioral phenotypes were evaluated in a fully balanced and synchronized study using a completely automated behavioral phenotyping device (IntelliCage). Activity pattern and spatial conditioning performance differed consistently between strains, i.e. exhibited no interaction with the between-laboratory factor, whereas the gross laboratory effect showed up significantly in the majority of measures. It is argued that overall differences between laboratories may not realistically be preventable, as subtle differences in animal housing and treatment will not be controllable, in practice. However, consistency of strain (or treatment) effects appears to be far more important in behavioral and brain sciences than the absolute overall level of such measures. In this respect, basic behavioral and learning measures proved to be highly consistent in the IntelliCage, therefore providing a valid basis for meaningful research hypothesis testing. Also, potential heterogeneity of behavioral status because of environmental and social enrichment has no detectable negative effect on the consistency of strain effects. We suggest that the absence of human interference during behavioral testing is the most prominent advantage of the IntelliCage and suspect that this is likely responsible for the between-laboratory consistency of findings, although we are aware that this ultimately needs direct testing.

In many countries the process of toxicity testing of environmental chemicals is ruled by a framework of OECD guidelines. The present paper will give an overview over the relevant OECD guidelines and guidance documents and mainly focus on methodological issues related to the prenatal toxicity testing guideline. Relevant guideline text will be provided, and practical recommendations will be given both for critical issues of experimental methodology and data interpretation.

The objective of juvenile animal toxicity studies of pharmaceuticals is to obtain safety data, including information on the potential for adverse effects on postnatal growth and development. Studies in juvenile animals may assist in identifying postnatal developmental toxicities or other adverse effects that are not adequately assessed in the routine toxicity evaluations and that cannot be safely or adequately measured in pediatric clinical trials. Unlike the traditional reproductive and developmental toxicology studies that have been discussed in the accompanying reports, the design requirements for toxicity studies in juvenile animals are not explicitly defined in regulatory guidance. However, studies in juvenile animals can be useful in providing safety information necessary to enable pediatric clinical trials in pediatric patients or when there are special concerns for toxicities that cannot be safely or adequately measured in clinical trials. These juvenile animal toxicity studies are designed on a case-by-case basis. General design considerations and examples of study designs for assessment of juvenile animal toxicity are discussed.

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