Abstract
Background and aim: The academic research involving animal testing is struggling with problems of reproducibility and a few of the specific reasons pointed out are for example insufficient reporting of animal strains and protocol details. It is everyone’s responsibility to follow the 3R’s (Replace, Reduce, Refine) and to ensure that the model used is well characterized. In this work we investigated how activity data collected from automated home-cage monitoring can be used to characterize behavior patterns and how well the results could be reproduced in a multi-center setup. We also studied if we can detect changes in behavior patterns through aging, using the same system. Finally, the impact of dietary restriction on behavior patterns and activity levels.
Material and Methods: We used C57BL/6J male and female mice from young age and kept them in the study for as long as up to 70 weeks. Groups of both male and female mice were subjected to modest dietary restriction from the age of 3 months and throughout the study. The DVC TM system uses standard IVC cages and has an external board of sensor electrodes in each cage slot that can detect activity on the cage floor in cages of group-held mice.
Results and conclusion: By analyzing activity data from the DVC system we could identify daily activity patterns with increased activity during lights off and also around the time for lights on in the holding room. We could also document the impact of husbandry procedures such as cage change. In addition, we identified additional behavioral rhythms with weekly variations and, importantly, a seasonal-like oscillation in activity with highs and lows and a periodicity of about 40 days. We hypothesized that activity levels would decrease with increasing age, and there is a small but highly significant decrease in overall activity between young adulthood and middle age. Monitoring mice on dietary restriction, we show that the diet regime is able to completely change the activity patterns, but we were not able to detect clear differences in activity levels between dietary restricted and ad libitum fed mice.
