The dopamine D1 receptor agonists, A68930 and SKF 38393, induce arousal and suppress REM sleep in the rat

The effects of the dopamine D1 receptor full agonist, A68930, on sleep-wake patterns and grooming behaviour were studied in the rat. The partial dopamine D1 receptor agonist, SKF 38393, was used for comparison. A68930 (0.003-0.3 mg/kg s.c.) increased waking time, reduced the amount of rapid eye movement (REM) sleep and enhanced spontaneous grooming dose dependently. The ED50 were 0.06, 0.02 and 0.05 mg/kg, respectively. The D1 antagonist, SCH 23390 (0.003 mg/kg s.c.), blocked the effects of A68930 on wakefulness and grooming but not those on REM sleep. SKF 38393 (0.1-10 mg/kg s.c.) increased grooming with an ED50 of 1.4 mg/kg and a dose-response relationship similar to that of A68930 (potency ratio 28). Conversely, the increase of wakefulness and reduction of REM sleep caused by SKF 38393 had dose-response curves different from those of A68930. The results support the view that D1 receptors may have a physiological function in producing arousal.