Induction and resetting of REM sleep rhythm in normal man by arecholine: blockade by scopolamine.

Arecholine, a cholinergic muscarinic agonist, was administered intravenously 35 min after sleep onset in eight normal volunteers who had been pretreated with either methscopolamine or scopolamine, muscarinic receptor blockers that do not and do cross the blood--brain barrier, respectively. Following pretreatment with methscopolamine, arecholine shortened the REM latency and increased the number of REM periods without altering the duration of individual REM periods or altering the REM--REM intervals. Pretreatment with scopolamine blocked the effects of arecholine. The results support the hypothesis that cholinergic muscarinic mechanisms are involved in the timing but not the duration of REM sleep.