Cholinergic brainstem mechanisms of REM sleep in the rat.

Injection of carbachol into the brainstem of rats produced an increase in rapid eye movement (REM) sleep which was site- and dose-dependent. Effective locations for carbachol to stimulate REM sleep included the pontine reticular formation at the level of the trigeminal motor nucleus and the dorsal parabrachial area in the caudal midbrain. The carbachol effect in the caudal pons was dose-dependent. Additionally, this effect was blocked by concomitant administration of the muscarinic antagonist atropine. Control experiments suggested that the drug-induced phenomenon appeared to be an increase in normal physiological REM sleep.