Adrenergic alpha(2) agonist (clonidine) and its antagonist (yohimbine)
were locally applied to the medial preoptic area (mPOA), to find out
the role of alpha(2) receptors at this brain region in the regulation
of sleep-wakefulness. Clonidine produced arousal, whereas yohimbine in
duced sleep in freely moving animals. Behavioural arousal produced by
clonidine administration was accompanied by EEG synchronization. The a
lpha(2) receptors as the probable site of action of externally applied
norepinephrine (NE), is discussed.