Effects of a D-2 receptor agonist RO 41-9067 alone and with clonidine on sleep parameters in the rat

The effects of RO 41-9067, a D-2 dopamine receptors agonist, on different sleep parameters were studied in the rat. RO 41-9067 dose dependently decreased paradoxical sleep, and only at the higher dose increased waking during the light period. In contrast, the higher dose of RO 41-9067 increased paradoxical sleep and decreased waking during the dark period. Finally, the combination of RO 41-9067 and clonidine significantly prevent the decrease of total sleep time and paradoxical sleep found after clonidine alone. These results, compared with those of classical D-2 dopamine receptors agonists, suggest an action for RO 41-9067 on D-2 dopamine receptors depending on the cerebral structure, a different action particularly on the striatum and/or on the structures responsible for paradoxical sleep. An active role for D-2 dopamine receptors and an interaction between noradrenergic and dopaminergic systems in the regulation of sleep is proposed.