Noradrenaline is involved in the regulation of the sleep/waking cycle by acting through various receptor types. In previous studies we investigated the role of beta- and alpha 2-adrenergic receptors through local microinjections of various drugs into the dorsal pontine tegmentum (DPT) of the cat. This region is known to be crucially involved in desynchronized sleep execution. In this study we examined the role of alpha 1-adrenergic receptors. The alpha 1-agonist methoxamine and the alpha 1-antagonist prazosin were injected into the DPT of freely moving, unanaesthetized cats. We found that methoxamine notably reduced desynchronized sleep, and that this effect was both dose-dependent and site-specific. These effects were prevented by the subsequent injection of prazosin. On the other hand, the injection into the DPT of prazosin alone produced scarce or inconsistent effects on the sleep/waking cycle.