Rapid eye movement (REM) sleep deprivation and auditory stimulation (A
DS), separately, increase REM sleep in rats, cats and humans. The main
goal of the present study was to test whether administration of ADS d
uring REM sleep rebound has a synergistic effect on REM sleep elicitat
ion. Male Wistar rats were implanted with standard sleep recording ele
ctrodes. Following the recovery period, animals were randomly assigned
to the following conditions: undeprived (i.e. control) and 24, 48, 96
and 120 hours of REM sleep deprivation by the platform method. Undepr
ived and REM sleep-deprived animals were divided into two groups, with
and without ADS. ADS was a ''beep'' of 80 dB and 2,000 Hz, lasting 20
msec every 10 seconds. This stimulus was applied for the first 4 hour
s of sleep recordings after deprivation. After that, animals were reco
rded for another 4 hours. In the undeprived situation, the group that
received ADS increased REM sleep approximately 70% above the group tha
t did not receive ADS, as has been reported previously (REM sleep with
out ADS: 38.1 +/- 13.84 vs. with ADS: 64.6 +/- 11.8, p < 0.005). No sy
nergistic effect was observed between REM sleep deprivation and ADS fo
r any REM sleep-deprivation schedule. This result may be explained as
an increase in the excitability pattern of pontine neurons and/or chan
ges in the cholinergic system due to REM sleep deprivation that could
not be further increased by ADS.