Marble burying and spontaneous motor activity in mice: interactions over days and the effect of diazepam

Spontaneous motor activity of mice was studied in the presence or absence of 24 coloured glass marbles with and without treatment with different doses of the anxiolytic compound, diazepam. The three parameters of motor activity, locomotion, rearing and total activity, were measured in automated test cages. All the groups exposed to the marbles exhibited considerable and comparable marble burying, but there was an important interaction between marble burying and locomotor activity over test days. The "marbles" group performed fewer locomotion counts than the "no marbles" group on Day 1 but more counts on Day 3. The "marbles" group performed more rearing and less total activity than the "no marbles" group generally and this relationship was not altered over test days. Diazepam caused a dose-dependent decrease of both marble burying and the three parameters of motor activity but did not cause further increases in motor activity in the groups exposed to the marbles. These results are discussed with regard to the effects of "coping" behaviours on measures of motor activity. In conclusion, the present motor activity-marble burying test appears to be a suitable animal model for testing potential anxiolytic compounds.