Abstract

It has been proposed that central nervous system norepinephrine (NE) is essential for the occurrence of rapid eye movement (REM) sleep. We have tested this hypothesis by treating eats with α-metiivltvrosine (α-MT), a drug that lowers brain catecholamine levels by inhibiting the rate-limiting step in catecholamine biosynthesis. In one series of cats. doses ranging from 3.125 to 400 mg/kg and placebo were given, i.p. The drug elevated REM sleep. both absolute minutes and percentage. In a separate set of cats, α-MT (100 mg/kg i.p.) was found to lower NE levels in various regions of the brain. Also, one of the original cats used for the electroencephalographic studies was given α-MT, 100 mg/kg, then sacrificed after eight hours of electroencephalographic recording and the brain analyzed for NE. While REM sleep was elevated, brain NE was depressed. We conclude that in cats whose NE levels have beeti reduced by as much as 70% in brain areas said to be responsible for tile active processes of REM sleep, REM sleep can nevertheless occur in increased amounts. This does not support the NE hypothesis of REM sleep. It also shows that the sedation produced by αMT is akin to the deeper phases of natural sleep.