The D1 dopamine receptor antagonist SCH 23390 enhances REM sleep in the rat

The effect of the D1 dopamine receptor antagonist SCH 23390 on sleep patterns was studied in rats by means of the electroencephalographic (EEG) technique. Haloperidol, an established D2 antagonist neuroleptic, was used for comparison. Over a very small dose range (0.003-0.03 mg/kg, subcutaneously), SCH 23390 significantly increased the time spent in total sleep, including rapid eye movement (REM) and non-REM sleep. The magnitude of the overall change of REM sleep was considerably greater than that of non-REM sleep. Enhancement of the amount of REM was characterized by increase in number of episodes but no change of latency to the first period of REM. Haloperidol increased non-REM sleep at 0.3-3 mg/kg, orally, but did not affect other measures of REM. Considering the small dose range at which SCH 23390 was effective, and the fact that REM and non-REM sleep may be unrelated events, it is suggested that promotion of REM sleep is a specific effect induced by selective blockade of D1 receptors.