Natural hypothermia and sleep deprivation: common effects on
recovery sleep in the djungarian hamster.
Deboer, Tom, and Irene Tobler.
Institute of Pharmacology, University of Z[umlaut]urich,
Z[umlaut]urich, Switzerland
APStracts 3:0196R, 1996.
Sleep, daily torpor, and hibernation have been considered to be
homologous processes. However, in the Djungarian hamster, daily
torpor is followed by an increase in slow-wave activity (SWA; EEG
power density 0.75-4.0 Hz) which is similar to the increase observed
after sleep deprivation. A positive correlation was found between
torpor episode length and the subsequent increase in SWA which was
highest when SWA was assumed to increase with a saturating
exponential function. Thus the increase in SWA propensity during
daily torpor followed similar kinetics as during waking, supporting
the hypothesis that when the animal is in torpor it is incurring a
sleep debt. An alternative hypothesis, proposing that the mode of
arousal causes the subsequent SWA increase, was tested by warming the
animals during emergence from daily torpor. Irrespective of mode of
arousal more NREM sleep and a similar SWA increase was found after
torpor. The data are compatible with a putative neuronal restorative
function for sleep associated with the expression of SWA in NREM
sleep. During torpor, when brain temperature is low, this function is
inhibited, whereas the need for restoration accumulates. Recovery
takes place only after return to euthermia.
Received 16 November 1995; accepted in final form 1 May 1996.
APS Manuscript Number R720-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96