Effects of sleep deprivation on sleepiness and increased REM sleep in rats selectively bred for cholinergic hyperactivity.

In this study we employed a modification of the multiple sleep latency test (MSLT) to determine whether rats of a strain with increased cholinergic activity were sleepier compared to randomly bred control rats. Seven rats each from the Flinders sensitive line (FSL, hypercholinergic) and Flinders resistant line (FRL, age-matched controls) were kept awake for 20 min and then allowed to sleep ad libitum for 20 min. The regimen of 20 min of wakefulness followed by 20 min of sleep was repeated 12 times during the day. There were no differences in latency to sleep or to rapid eye movement (REM) sleep or in percent total sleep time, drowsy, or slow-wave sleep between FSL rats and FRL rats. However, FSL rats showed a significant increase in REM sleep compared to FRL rats. This selective increase in REM sleep may be coupled to an increase in brain muscarinic receptors in the FSL rats.