The role of fever in appetite suppression after endotoxin administration.

In order to test the hypothesis that fever, and not some other aspect of the acute phase response, decreases food intake after administration of endotoxin, food intake of rats was studied under conditions of 1) fever, 2) antipyresis, and 3) endotoxin tolerance. Injection of endotoxin resulted in a significant elevation in rectal temperature and a significant reduction in food intake. Administration of the antipyretic drug sodium salicylate to endotoxin-injected animals lowered rectal temperatures to control levels, but food intake was still suppressed. When rats were made tolerant to endotoxin by repeated injections, an attenuated fever was observed, and food intake was not significantly different from that of control animals. We conclude that the effects of endotoxin on body temperature can be dissociated from its effects on food intake. We speculate that the failure of endotoxin to suppress food intake in endotoxin-tolerant rats may be due to a decreased production of endogenous pyrogen.