ENHANCEMENT OF RAPID EYE-MOVEMENT SLEEP IN THE RAT BY CHOLINERGIC ANDADENOSINERGIC AGONISTS INFUSED INTO THE PONTINE RETICULAR-FORMATION

The cholinergic agonist carbachol (1.1 mM) and the adenosinergic agoni st cyclohexyladenosine (0.1 mM) were microinjected (60 nl) into the re gion of the caudal, oral pontine reticular formation of the rat. Local intracerebral infusion of each receptor agonist resulted in significa nt, long-lasting (at least 8 h) elevations in rapid eye movement sleep without reduction in latency to onset. The effects of carbachol were reduced by the muscarinic receptor antagonist atropine, while those of cyclohexyladenosine were reduced by the adenosinergic receptor antago nist 8-cyclopentyltheophylline. Atropine failed to antagonize the long -term induction of rapid eye movement sleep following cyclohexyladenos ine, but did appear to suppress increases in the first 2 h. Similarity of effects on sleep parameters and the lack of additivity when inject ed consecutively are consistent with these agonist ligands targeting t he same cellular mechanisms through their respective receptors. These findings suggest that transitory increases in the pens of either acety lcholine or adenosine may underlie Long-lasting elevations in the amou nt of rapid eye movement sleep. Adenosine may play a role in the incre ased rapid eye movement sleep following prolonged wakefulness, as well as following conditions of stress and learning. (C) 1998 IBRO. Publis hed by Elsevier Science Ltd.