Effects of the selective alpha 1-adrenoceptor blocker prazosin on EEG sleep and waking stages in the rat.

In order to gain a better understanding of the role of the noradrenergic system in the control of the EEG sleep-waking stages, the effects of the selective alpha 1-antagonist prazosin was investigated in the rat. Oral doses of prazosin (0.1-10 mg/kg) were administered that have been shown to enter the brain. EEG sleep and waking stages were recorded either during 8 h after drug administration at 8.00 in the morning or during 48 h after drug administration at 16.00 in the afternoon. It was found that prazosin at doses of 0.1-10 mg/kg shortened quiet waking. Starting at 1 mg/kg paradoxical sleep (PS) was shortened and, most interestingly, active waking and slow wave sleep (SWS) were prolonged. PS spindles and dozing were shortened after a latency of some hours during the 48-hour experiment. However, during the 8-hour experiment PS spindles were prolonged at 0.32 and 1 mg/kg. These data suggest that in the rat alpha 1-adrenoceptor inhibition in the brain allows the occurrence of active waking and SWS and suppresses PS.