Nicotine and fluoxetine induce arousing effects on sleep–wake cycle in antidepressive doses: A possible mechanism of antidepressant-like effects of nicotine

A number of studies have reported an association between smoking and depression, and several reports suggest that nicotine (NIC) may act as an antidepressant. The present study was designed to determine whether the effects of NIC on sleep–wake patterns in rats are similar to those of the antidepressant fluoxetine (FLX), a selective serotonin reuptake inhibitor. Male rats were chronically implanted with a standard set of electrodes for sleep recording. We compared the effects of antidepressive doses of NIC, FLX and the combination of both drugs on sleep–wake pattern in rats subjected to one day, one week and two weeks of administration, as well as after the withdrawal of the two-week treatment. The changes observed in our study in an 8-h sleep recording period during one day, one week and two weeks of NIC administration are very similar to those observed in the rats that received FLX, which led to a decrease in both slow wave sleep II and rapid eye movement (REM) sleep as a consequence of an increase in wakefulness. In addition, all treatments also induced a significant lengthening of REM sleep latency onset. These data suggest that the antidepressant-like action of NIC could be caused by its arousing properties.