Journal of Applied Physiology, Vol 59, Issue 4 1254-1257, Copyright © 1985 by American Physiological Society
A study of the variability in the febrile responses of rabbits to endogenous pyrogen
J. T. Stitt
The range of body temperature increases elicited by a standard dose of
endogenous pyrogen (0.5 ml/kg iv) was examined in a population of 26 male
New Zealand White rabbits. Although the mean maximum increase in rectal
temperature was 0.88 +/- 0.06 degree C (SE), individual responses varied
from 0.4 degree to 1.5 degree C. Three representative animals that
responded to the standard dose of pyrogen with small, intermediate, and
large febrile responses were selected and challenged with the same dose of
pyrogen on eight separate occasions, and the variability of these responses
was examined. There was little variability within the characteristic
responses of any particular animal to the repeated challenges. The
variability of the febrile responses elicited by both intravenous and
intracerebroventricular administration of the same pyrogen was examined and
compared using another group of 11 rabbits. The variability in response to
the intravenous route was similar to that found in the larger population,
whereas the variation in response to the intracerebroventricular route was
smaller, and all 11 animals had fevers that were greater than 1 degrees C.
It is concluded that the variability of the febrile responses of rabbits to
intravenous pyrogen was due to differences between individual sensitivities
of animals to the intravenously administered pyrogen. This difference in
sensitivity may be due to a difference in the amount of pyrogen that
reaches the putative receptor sites, or to a difference in the density or
effectiveness of receptor sites in translating the pyrogenic stimulus into
a fever response.
