Effect of interleukin-1b on eeg power density during sleep depends
on circadian phase..
Lancel, Marike, Stefan Mathias, Johannes Faulhaber, and Thomas
Schiffelholz.
Max-Planck Institute of Psychiatry, Dept. of Neuroendocrinology,
Clinical Institute, D-80804 Munich
APStracts 2:0317R, 1995.
The cytokine interleukin-1 (IL-1) is a key mediator of the somnogenic
response to immune challenge. In this vehicle-controlled study we
evaluated circadian interference with the sleep promoting effects of
IL-1b. In two randomized experiments, rats were injected
intracerebroventricularly with 5 ng IL-1b either at the beginning of
the rest phase or at the beginning of the activity phase. Recordings
were made during 24 hours preceding the injections (baseline) and
during the first 12 post injection hours. To avoid masking effects of
light, the rats were maintained under a skeleton photoperiod during
recording. During both the rest and activity phase, IL-1b induced
fever and initially promoted nonREMS and suppressed REMS. The effect
of IL-1b on the duration of nonREMS and EEG power densities within
nonREMS was related to circadian phase. During the rest phase, IL-1b
resulted in a minor increase in nonREMS-duration but a prominent
enhancement in EEG activity in the delta (0.5-4 Hz), and most other
frequency bands. During the activity phase, IL-1b evoked a larger
increase in the duration of nonREMS, but hardly affected EEG activity
within this state. Thus, the effects of IL-1b on nonREMS are strongly
influenced by diurnal phase. The alterations in EEG power density are
in contrast to those elicited by sleep deprivation, which are largely
independent of time of day. It is concluded that IL-1b activates EEG
regulatory mechanisms mediated by processes which depend on circadian
phase.
Received 7 August 1995; accepted in final form 7 November 1995.
APS Manuscript Number R499-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95