Effects of morphine on sleep in the cat

The effects of morphine sulfate, 300 g/kg s.c., on the sleep of cats was studied by electroencephalographic techniques. In contrast to placebo experiments the animals were awake for approximately 6 h after administration of morphine; the return of regular sleep patterns occurred after about 11 h. A rebound increase in rapid eye movement (REM) sleep time and percentage was noted during the 11th through the 17th hour of the study. Sleep following manual sleep deprivation for 10 h showed a rebound increase in REM and non-rapid eye movement (NREM) sleep time. NREM sleep rebound after manual sleep deprivation exceeded that occurring after morphine. The alerting actions of morphine could be blocked by naloxone, 100 g/kg s.c., for about 90 min. Naloxone alone increased REM sleep time and percentage. Single (84 mg/kg) or multiple (51 mg/kg for 4 injections) doses of dl--methyltyrosine i.p. did not block the alerting action or REM sleep rebound caused by morphine. 5-Hydrotryptophan (30 mg/kg) i.p. did not antagonize the alerting action of morphine.Publication No. 1044 of the Division of Basic Health Sciences of Emory University. A preliminary report of this work was presented at the Fall Meeting of the American Society for Pharmacology and Experimental Therapeutics, Pittsburgh, Pennsylvania, August, 1969. This work was supported by USPHS grant MH12870-04.A predoctoral fellow of Graduate Pharmacology Training Grant 2T1-GM179.