INDUCTION OF RAPID EYE-MOVEMENT SLEEP BY CARBACHOL INFUSION INTO THE PONTINE RETICULAR-FORMATION IN THE RAT

CHOLINERGIC regulation of sleep and wakefulness was studied in freely moving rats locally infused with various doses of carbachol into the p ontine reticular formation. Induction of REM sleep occurred when carba chol was infused specifically into the posterior oral pontine reticula r nucleus (PnO). This effect was observed with 1-10 ng of carbachol, a nd lasted for at least 6 h. It was antagonized by atropine (100-200 ng ) infused into the same site 15 min before carbachol (10 ng), indicati ng that REM sleep induction resulted from the stimulation of pontine m uscarinic receptors. High doses of carbachol (500 ng) did not affect R EM sleep but enhanced wakefulness. Cholinergic mechanisms within the P nO may play a critical role in the regulation of REM sleep in the rat.