The effects of clonidine on EEG wavebands associated with sleep in the rat.

Clonidine was studied for its effects in rats on the occurrence of several EEG waves that characterize the sleep/waking cycle. Intraperitoneal administration of the drug (0.001-1.0 mg/kg) at the onset of the daily light period induced low frequency (4-7 Hz) rhythmical slow activity (RSA), and suppressed delta-wave occurrence. These effects were more prominent with increasing dose. Clonidine also had a biphasic effect on spindles: at low doses it suppressed, while at high doses it enhanced spindle occurrence. These effects could not be characterized as modifications in any of the classical sleep stages. A clearly non-classical state was induced by the clonidine in these studies. These results suggest that in rat, effects of clonidine cannot simply be interpreted as an alteration in one or more of the classically-defined sleep states.