Microinjections of nicotine in the medial pontine reticular formation elicits REM sleep.

Microinfusion of non-specific cholinergic muscarinic-nicotinic agonists, such as carbachol, into the medial pontine reticular formation readily elicits REM sleep. It has generally been assumed that muscarinic receptors mediate the action of cholinergic agonists in triggering rapid eye movement (REM) sleep. Very little is known, however, about the role of nicotinic mechanisms in REM sleep generation. In this study, we administered nicotine and Ringer's solution into the medial pontine reticular formation of freely moving cats. Compared to control Ringer's injections, nicotine increased REM sleep and decreased wake and slow wave sleep (SWS) I percentage. Nicotine also shortened the time to REM sleep onset. These findings suggest a role of nicotinic mechanisms in REM sleep generation.