Presence of a paradoxical sleep (PS) factor in the cerebrospinal fluid of PS-deprived rats.

The lack of paradoxical sleep (PS) observed in rats after pharmacological blockade of the noradrenergic beta-receptors was reversed by intraventricular infusion of cerebrospinal fluid (CSF) from PS-deprived donor rats. The PS restoration in recipient animals was proportional to the duration of the deprivation in donors. It is concluded that some PS-inducing factor progressively accumulates in the CSF during deprivation. This factor acts beyond the noradrenergic step in the regulation of PS.