AJP - Regulatory, Integrative and Comparative Physiology, Vol 272, Issue 2 682-R690, Copyright © 1997 by American Physiological Society
Operant control of ambient temperature during sleep deprivation
P. J. Shaw, B. M. Bergmann and A. Rechtschaffen
Department of Psychiatry, University of Chicago, Illinois 60637, USA.
Rats subjected to total sleep deprivation (TSD) by the disk-over-water
method were provided with a continuously available operant by which they
could increase ambient temperature (T(amb)). TSD rats progressively
increased operant responses for heat to 700% of baseline levels. During the
last quarter of sleep deprivation, they maintained mean T(amb) at 9 degrees
C above baseline and held T(amb) over 40 degrees C for 35% of the day. In
contrast, yoked control rats (TSC) did not change mean T(amb). Although
both TSD and TSC rats showed a progressive decline in intraperitoneal
temperature (T(ip)), TSD rats maintained an elevated T(amb) even during
periods when T(ip) and brain temperatures (T(br)) were above baseline
levels. Thus these results confirm and extend earlier findings that rats
subjected to TSD show an increase in temperature set point (T(set)). The
earlier studies, which utilized short daily trials in a thermal gradient,
demonstrated an increase in T(set) early in the deprivation period. The
present study, which obtained more extensive data on thermal preference at
a range of body temperatures demonstrated an increasing T(amb) for almost
all T(ip) and T(br) values, suggesting a progressive increase in T(set)
over the course of sleep deprivation. Surprisingly, survival time was
shorter than in previous TSD studies. Reduced survival could not be
attributed to differences in T(br), T(ip), energy expenditure, or sleep
loss from previous studies.
