Changes in sleep after acute and repeated administration of nicotine in the rat

Rationale: Acetylcholine clearly Flays a role in regulating sleep. This influence may involve nicotinic systems because several studies have demonstrated that nicotine treatment alters sleep. However, the literature that suggests an effect of nicotine treatment on sleep is contradictory, perhaps because different doses and routes of administration were used. Objective: The studies reported here evaluated the effects of several doses of nicotine on REM sleep in the rat. Methods: Male Wistar rats were prepared with a set of sleep recording electrodes and, following habituation to the test chamber, were used in one of three studies: a) a dose-response analysis of an acute dose of nicotine on REM sleep measured during the first 4 h after injection; b) a chronic treatment experiment; or c) a mecamylamine blockade experiment. Results: Acute nicotine administration decreased REM sleep in a dose-dependent fashion; significant effects were observed following injection with the 0.5 and 1.0 mg/kg doses. A decrease in slow wave sleep and an increase in wakefulness were also observed. Mecamylamine by itself did not affect REM sleep, but it blocked the effects on sleep produced by nicotine when given 30 min before a 1 mg/kg dose of nicotine. Rats that had been injected once daily with a 0.1 mg/kg dose of nicotine showed an increase in REM sleep after the third injection, whereas rats that had been chronically treated with a higher dose (0.5 mg/kg) displayed a reduction in REM and total sleep time. Conclusion: These findings argue that the effects of both acute and chronic nicotine treatment on sleep are influenced by the dose of nicotine used.