Diazepam modulates the period of locomotor rhythm in mice (Mus booduga) and attenuates light-induced phase advances.

Experiments were carried out on the continuous action of diazepam (benzodiazepine) offered through drinking water in 2% ethanol on psi and tau of the activity rhythms under LD (12:12) and DD conditions. Under entraining conditions diazepam failed to evoke striking changes in psi. On the other hand, under free-running conditions period-lengthening and period-shortening effects were observed. Further experiments conducted on the continuous effect of diazepam on light pulse evoked phase shifts revealed that phase advances were attenuated significantly in diazepam-treated animals at CT 20 and 24. These results were discussed with regard to the action of diazepam on the light sensitivity of the circadian pacemaker.