Chronic exercise conditioning has been shown to alter basal thermoregulatory processes as well as the response to inflammatory agents. Two such agents,
lipopolysaccharide (LPS) and
turpentine (
TPT) are inducers of
fever in rats. LPS, given intraperitoneally (i.p.), involves a systemic inflammatory response whereas
TPT given intramuscularly (i.m.) elicits a localized
inflammation. We assessed if chronic exercise training in the rat would alter the thermoregulatory response to LPS and
TPT. Core temperature (T (c)) and motor activity were monitored by radiotelemetry. Female Sprague Dawley rats were divided into two groups (trained and sedentary) and housed at an ambient temperature of 22 degrees C. Animals voluntarily trained on running wheels for 8 weeks. In the first study, trained and sedentary female rats were injected i.p. with LPS (50 microg/kg) or an equal volume of 0.9%
normal saline. In another study, trained and sedentary female rats were injected i.m. with
TPT (10 microl)/rat or an equal volume of 0.9%
normal saline. The time course of the LPS
fever was very short compared to
TPT.
TPT injected animals displayed a smaller but more prolonged
fever compared to LPS; however, training accentuated the febrile response to LPS (DeltaT (c)=0.6 degrees C in sedentary and 1.2 degrees C in trained). Training had a slight suppression on
TPT-induced
fever during the daytime but had no effect on motor activity or nighttime T (c). In contrast, exercise training led to a marked increase in the pyrogenic effects of LPS. We conclude that the effect of exercise training and source of
infection (i.e., systemic versus localized in muscle) on
fever is directly linked to type of pyrogenic agent.