Brain dopamine receptors and sleep in the rat: effects of stimulation and blockade.

A high dose of apomorphine, a stimulator of brain dopamine receptors, caused a reduction in total sleep, intermediate sleep and a delayed appearance of paradoxical sleep. With a lower dose, a small and not significant trend toward an increase of paradoxical sleep was observed. Spiroperidol, considered as a specific blocker of dopamine receptors, produced a dose-dependent increase of total sleep and a decrease of paradoxical sleep. Chlorpromazine induced a different effect, that is a clear enhancement of paradoxical sleep. Taken together, these results indicate that an activation of dopamine systems in the brain is partly involved not only in behavioral activation, but also in cortical activation of waking and paradoxical sleep. The effect of chlorpromazine on paradoxical sleep cannot be attributed to the antidopaminergic properties of this drug.