Behavioral traits are affected by selective breeding for increased wheel-running behavior in mice

Abstract

Voluntary physical activity may be related to personality traits. Here, we investigated these relations in two mouse lines selectively bred for high voluntary wheel-running behavior and in one non-selected control line. Selection lines were more explorative and "information gathering" in the open-field test, either with increased upright positions or horizontal locomotion toward the middle ring. Furthermore, one of the selection lines had an increased risk-taking behavior relative to the control line in approaching a novel object placed in the center of the open field. However, anxiety behavior was increased in selection lines during the plus-maze test. Maze learning was not statistically different among lines, but routine behavior was increased in both selection lines when the maze exit after 2 days of testing was displaced. Specifically, in the displaced maze, selected mice traveled more frequently to the old, habituated exit, bypassing the new exit attached to their home cage. Although the generality of the results would need to be confirmed in future studies including all eight lines in the selection experiment, the increased routine and exploratory behavior (at least in the lines used in the present study) may be adaptive to sustain high activity levels.

Fig. 1

The complex maze adapted from Rabinovitch and Rosvold (1951), with the entry on the left hand side and the exit on the right

Fig. 2

Configuration of the complex maze during the first 2 days (a), and during the last trial on the third day (b), where the entrance and exit were laterally inverted. Note that the on the third day the mouse bypasses the “new” displaced exit (configuration b) when searching for the “old” exit (configuration a)

Fig. 3

Open-field behavior of mouse lines 2 (control), 7 (selectively bred for high voluntary wheel running), and 8 (also selected) during the first 4 min (left panels) and during the last minute after which a novel object was introduced in the center of the open field (right panels). The top panels show the percentage of time the animals spent in the different areas, the middle panels show the number of visits to the different areas, and the lower panels show the total number of rearings. * indicate significant difference between means at p < 0.05

Fig. 4

Plus-maze behavior of mouse lines 2 (control), 7 (selectively bred for high voluntary wheel running), and 8 (also selected). Top panel shows the percentage of time spent in the open arms, closed arms and in the center. Middle panel shows the percentage of arm entries into the open and closed arms. Lower panel shows total arm entries. Asterisks indicate significant difference between means at p < 0.05 (*), and p < 0.01 (**)

Fig. 5

Complex maze behavior of mouse lines 2 (control), 7 (selected), and 8 (selected) on first day (left panels), and on the second day (right panels). Top panels show the duration in the maze to find the exit, and the lower panels show the number of mistakes the mice made. * indicate significant difference between means at p < 0.05

Fig. 6

Complex maze behavior of mouse lines 2 (control), 7 (selected), and 8 (selected) during the final trial on the third day during which the entrance and exit were inverted laterally. Top panel shows the time spent in the maze. The middle panel shows the number of mistakes the mice make in the maze, and the lower panel shows the percentage of mice going directly at the first attempt to the new inverted exit. * Indicate significant difference between means at p < 0.05