GABAergic hypnotics are known to depress non-rapid eye movement delta and r
apid eye movements and to stimulate non-rapid eye movement sigma (spindles)
and beta EEG. This study addressed the question of whether the magnitudes
of these effects are significantly correlated. Data were from a study in 16
normal subjects whose sleep was recorded for five nights under placebo and
for three nights each under zolpidem (10 mg), triazolam (0.25 mg) and tema
zepam (30 mg). EEG was analyzed with both period-amplitude and power spectr
al (FFT) analysis. The magnitudes of the EEG and eye movement density respo
nses were not significantly correlated for any of the three drugs. It is th
erefore unlikely that sleep responses to GABAergic drugs can be explained b
y the common cellular action (increased chloride conductance) of these drug
s. We suggest that the sleep EEG responses are manifestations of complex (b
ut consistent) interactions of excitation and inhibition in large brain sys
tems although certain aspects of these responses (e.g. the different time c
ourses of delta vs sigma and eye movement responses) may reflect molecular
adaptations. A separate observation in this study was the strong traitlike
characteristics of the sleep variables studied. These variables were highly
correlated across nights of baseline sleep; in addition, individual differ
ences in baseline sleep were significantly retained on the third night of t
emazepam administration. (C) 2000 Elsevier Science Ltd. All rights reserved
.