Exploring test batteries for depression- and anxiety-like behaviours in female and male ICR and black Swiss mice.

Objective and rationale: Animal models are critical for the study of mental disorders and their treatments but are repeatedly criticized for problems with validity and reproducibility. One approach to enhance validity and reproducibility of models is to use test batteries rather than single tests. Yet, a question regarding batteries is whether one can expect a consistent individual behavioural phenotype in mice across tests that can be presumed to be part of the same construct. This study was designed to explore the relationship between the behaviours of mice across tests in some variations of test batteries for depression- and anxiety-like behaviours. Methods: Female and male healthy, intact, and untreated mice from the ICR and black Swiss strains were used in four separate experiments. With some variations, mice were exposed to a battery of behavioural tests representing affective- and anxiety-like behaviours. Data were analysed for differences between sexes and for correlations between behaviours within and across the tests in the battery. Results: No differences were found between the sexes. With very few exceptions, we found correlations within tests (when one test has more than one measure or is repeated) but not across different tests within the battery. Conclusions: The results cast some doubt on the utility of behavioural test batteries to represent different facets of emotional behaviour in healthy intact outbred mice, without any interventions or treatments. Additional studies are designed to explore whether stronger relationship between the tests will appear after manipulations or drug treatments.

Individual variability in female and male mice in a test-retest protocol of the forced swim test.

BACKGROUND: The challenges to embody the complexity of symptoms and biological mechanism of affective disorders question the value of animal models as well as their reproducibility and validity. Validity is further hindered by large individual variability in many models. Whereas individual variability presents a challenge, it can also be used to study susceptibility and resistance. One of the frequently used models for screening antidepressants and interventions related to depression is the forced swim test (FST). The FST is typically performed only once. METHODS: The current study was designed with a number of objectives: (1) Examine the group effects of repeated FST (2) Examine the interaction between sex and repeated FST and (3) examine the consistency of individual variability across test and retest in the FST. We exposed ICR female and male mice to the FST 3 or 5 times with two days between exposures. Immobility time was analyzed across exposures at the group and the individual levels using repeated measures ANOVA as well as Pearson's correlations. RESULTS: As expected, repeated exposure to the FST resulted in increased immobility across exposures with no consistent effect of sex. At the level of individual mice, immobility time showed correlation across exposures. DISCUSSION: The current study demonstrates the effects of repeating the FST in both sexes with attention to individual variability. The results suggest that the FST can be used more than once and that mice show a consistent individual pattern of responding in the test.