AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 3 499-R507, Copyright © 1988 by American Physiological Society
Pyrogenicity of interferon and its inducer in rabbits
S. J. Won and M. T. Lin
Department of Microbiology and Physiology, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China.
The effects of intracerebral administration of interferon (IFN) or its
inducer polyriboinosinic acid-polyribocytidylic acid (poly I:C) on
thermoregulatory responses were assessed in conscious rabbits.
Administration of IFN (10(2)-10(6) IU) or poly I:C (0.012-12 micrograms)
into the preoptic anterior hypothalamus or the third cerebral ventricle
caused a dose-dependent fever in rabbits at three ambient temperatures (Ta)
tested. In the cold (Ta = 8 degrees C), the fever was due to increased
metabolism, whereas in the heat (Ta = 32 degrees C) the fever was due to a
reduction in respiratory evaporative heat loss and ear skin blood flow. At
the moderate environmental temperature (Ta = 22 degrees C), the fever was
due to increased metabolism and cutaneous vasoconstriction. Compared with
the febrile responses induced by cerebroventricular route injection of IFN
or poly I:C, the hypothalamic route of injection required a much lower dose
of IFN or poly I:C to produce a similar fever. Furthermore, the fever
induced by intrahypothalamic injection of IFN or poly I:C was reduced by
pretreatment of animals with a systemic dose of indomethacin (an inhibitor
of all prostaglandins formation) or cycloheximide (an inhibitor of protein
synthesis). The data indicate that IFN or its inducer may act through the
endogenous release of a prostaglandin or a protein factor of an unknown
chemical nature in the preoptic anterior hypothalamic region to induce
fever in rabbits. The fever induced by IFN or its inducer is brought about
by a decrease in heat loss and/or an increase in heat production in
rabbits.
