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Summary: SLEEP, Vol. 29, No. 10, 2006 1327
LOCUS COERULEUS AND AROUSAL
INTRODUCTION
THE IMPULSE ACTIVITY OF NORADRENERGIC LC
NEURONS DURING WAKEFULNESS PROGRESSIVELY
DECREASES DURING SLOW WAVE SLEEP (SWS) AND
becomes practically silent during paradoxical sleep (PS), reflect-
ing interactions with other aminergic, peptidergic, GABAergic,
and cholinergic systems in the hypothalamus and brain stem.1,2,3
Multidisciplinary studies have shown that a decrease in LC ac-
tivity facilitates sleep, whereas activation of LC neurons drives
wakefulness and modulates associated behaviors such as atten-
tion, performance, stress, and anxiety.2
In agreement with these
findings, a specific lesion of the noradrenergic LC system by N-
(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) facilitates
SWS and decreases wakefulness during the active period in rats
kept in light-dark (LD) conditions.4
It has also been shown that
noradrenergic LC neurons fire tonically faster during the active
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