Activity of Inbred and F 1 Mice in a Residential Maze

Male mice of strains A 2 G/Tb, C 57 BL/Tb and the F 1 produced by crossing them were studied singly for 3 days in an artificial environment (a “plus-maze”), in which movement was recorded automatically. There was a central nest box with an opaque cover, from which three passageways led to food, water and soft (balsa) wood, respectively; a fourth arm was left empty. The number of visits to the arms was always highest on the first day. On a given day, the number of visits was much the same for each arm, that is, it was not influenced by the incentives. In contrast, while time spent out of the nest box was about the same from day to day, the time spent in individual arms differed greatly and was in the order food> balsa wood> water> empty arm. In terms of visits, the F 1 and C 57 BL/Tb mice were more active than A 2 G/Tb; and the F 1 mice varied less than either inbred strain. The lack of correspondence between visits and duration of stay is discussed in relation to the concept of neophilia.