Alpha adrenergic system in medial preoptic area involved in sleep-wakefulness in rats.

The study is aimed at investigating the possible involvement of adrenergic mechanisms in the medial preoptic area (mPOA) for modulation of sleep-wakefulness in rats. In this study, saline, norepinephrine (NE), phenoxybenzamine (PBZ) and propranolol (PROP) were injected in the mPOA in different groups of male rats during the day and night. NE and PBZ were injected, during the day and the night respectively, in some control areas adjoining the mPOA in two other groups of animals. Arousal was produced by NE, and sleep by PBZ when they were applied in the mPOA. All other procedures, including application of NE and PBZ in the control areas and beta blocker (PROP) in the mPOA, did not produce alterations in sleep-wakefulness. These findings provide support for a physiological role played by the alpha adrenergic system in the mPOA for arousal, and area specificity of action of this system.