Locomotor activity pattern induced by diazepam in control and caffeine-treated mice

The effect of diazepam on locomotor activity was tested by measuring the number of crossings between two compartments of a toggle-floor box, in control mice (water drinking) and in mice receiving caffeine solution (0.5 g/I) instead of drinking water. In control mice, diazepam did not produce any significant change in total activity measured on the whole 60-min test, but animals showed phases of increased activity broken by periods of immobility. After chronic ingestion (18 days) of caffeine, doses of 0.5, 1 and 2 mg/kg ip diazepam significantly increased total locomotor activity. Caffeine slightly reduced diazepam-induced immobility and increased the frequency of crossings in active periods. Taken together, these two effects may explain the significant increase in total activity induced by diazepam in caffeine-treated mice. Mixed stimulatory-depressant action was also produced by 3 mg/kg diazepam, a dose that slightly decreased the total activity.