THE EFFECT OF A 3-DAY INCREASE OF AMBIENT-TEMPERATURE TOWARD THE THERMONEUTRAL ZONE ON RAPID EYE-MOVEMENT SLEEP IN THE RAT

This study examined the effect of a 3-day increase of ambient temperat ure (Ta) from the usual room temperature of 22 degrees C to the rat's thermoneutral zone (TNZ) of 29 degrees C on rapid eye movement (REM) s leep. Other laboratories have reported that brief increases of Ta to t he TNZ increased REM sleep and that long-term increases of Ta produced long-term increases of REM sleep. However, these studies were limited by the lack of controls for order effects or by restricted recording times. In the present study, which controlled for order effects, polys omnographic recordings for 12 male Sprague-Dawley rats were obtained 2 4 hours a day for 3 days at an ambient temperature of 22 degrees C and for 3 days at the TNZ of 29 degrees C. In all rats, REM sleep minutes and REM sleep percentage of total sleep time were significantly great er at the higher temperature than at the lower temperature. The increa se in REM sleep at 29 degrees C was stable over the 3-day recording pe riod. Prolonged increase of ambient temperature towards the TNZ is a s imple, nonpharmacological method of producing a sustained, significant increase of REM sleep in the rat.