On the role of brain alpha-adrenergic systems in the production of paradoxical sleep.

In order to reinvestigate the role of brain alpha-adrenergic systems in the regulation of paradoxical sleep (PS), we recorded chronically implanted rats under the effect of various neuroactive substances. The functions describing the evolution of PS during sleep were calculated. The following substances were studied at different doses, alone and in various combinations: clonidine, phenoxybenzamine, chlorpromazine, yohimbine, piperoxane and desipramine. Chlorpromazine, yohimbine, piperoxane and desipramine were also studied after pretreatment with alpha-methylparatyrosine. The results are discussed in terms of the known pharmacological properties of these compounds, and indicate that brain alpha-adrenergic systems, probably mainly noradrenergic systems, are positively involved in the maintenance of PS. However, the activity of these systems is controlled by powerful regulatory mechanisms: inhibitory control of transmitter release at the effector site, collateral inhibition within the locus coeruleus and control of transmitter release at the site of collateral inhibition.