SLEEP-INDUCING FUNCTION OF NORADRENERGIC FIBERS IN THE MEDIAL PREOPTIC AREA

The aim of the investigation was to find out the role of noradrenergic (NE) terminals of the medial preoptic area (mPOA), in the regulation of sleep-wakefulness. Studies were conducted on free-moving adult male rats with chronically implanted cannulae in the mPOA. Sleep-wakefulne ss was assessed on the basis of EEG, EMG, and EOG recordings along wit h behavioral observations. Lesioning of catecholamine terminals (with 6-hydroxydopamine) in the mPOA produced an increase in quiet wakefulne ss. Prevention of NE fiber destruction, by pretreating the rats with i mipramine, prevented this effect. This demonstrated that the increased quiet wakefulness produced by 6-OHDA was the result of NE fiber destr uction. Changes in sleep-wakefulness were also assessed after microinj ection of NE into the mPOA, in normal and ventral noradrenergic bundle (VNA)-lesioned rats. NE administration induced sleep in VNA-lesioned rats, and arousal in normal rats. The findings suggest that the NE ter minals in the mPOA, projecting via VNA, play a role in the induction o f sleep.