Voluntary Wheel Running in Mice

During the running wheel sessions, mice were single-housed and a running wheel (TSE Systems, Bad Homburg, Germany) was placed in each home cage (Type II long, Ebeco, Germany) in a dedicated room with the same light/dark cycle and environmental conditions as in the housing room. Data of 3 consecutive weeks of wheel running activity were automatically collected and processed with PhenoMaster software (TSE Systems). In week 1 and week 2, mice were exposed to a standard wheel, while during week 3 a “complex” wheel was introduced. This wheel has a fewer number of rods which are irregularly spaced, though with a predictable pattern (Liebetanz and Merkler, 2006 (link); Mandillo et al., 2014 (link)). Food and water were available ad libitum, and nestpaper was provided. Cages were changed every week. Wheel running activity for the 12 h dark phase was included in this study. Parameters measured were weekly values of: (1) total distance (m); (2) average run duration (s), where “runs” are running episodes at a velocity exceeding 30 rpm (~0.18 m/s); (3) average maximum speed (m/s) from daily values calculated as average of maximum speed values sampled every 5 min during the 12 h dark period; (4) total time on wheels (s).