AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 6 1125-R1132, Copyright © 1993 by American Physiological Society
Vigilance states, EEG spectra, and cortical temperature in the guinea pig
I. Tobler, P. Franken and K. Jaggi
Institute of Pharmacology, University of Zurich, Switzerland.
Vigilance states, electroencephalogram (EEG) power spectra (0.25-25.0 Hz),
and cortical temperature (TCRT) were obtained in nine guinea pigs for 24 h
in a 12:12-h light-dark (LD 12:12) schedule. Sleep was markedly polyphasic
and fragmented and amounted to 32% of recording time, which is a low value
compared with sleep in other rodents. There was 6.8% more sleep in the
light period than in the dark period. EEG power density in non-rapid eye
movement (NREM) sleep showed no significant temporal trend within the light
or the dark period. The homeostatic aspects of sleep regulation, as
proposed in the two-process model, can account for the slow-wave activity
(SWA) pattern also in the guinea pig: The small 24-h amplitude of the
sleep-wakefulness pattern resulted in a small, 12% decline of SWA within
the light period. In contrast to more distinctly nocturnal rodents, SWA in
the dark period was not higher than in the light period. TCRT showed no
difference between the light and the dark period. TCRT in REM sleep and
waking was higher than TCRT in NREM sleep. TCRT increased after the
transition from NREM sleep to either REM sleep or waking, and decreased in
the last minute before the transition and after the transition from waking
to NREM sleep. Motor activity measured in six animals for 11 days in
constant darkness showed no apparent rhythm in three animals and a
significant circadian rhythm in three others. Our data support the notion
that guinea pigs exhibit only a weak circadian rest-activity rhythm.
