Dissociation of temperature changes and anorexia after experimental colitis and LPS administration in rats

The acute phase of inflammation induces both anorexia and fever. Because several analyses suggest a linkage between the meal size and body temperature, we assessed whether temperature changes were causal to anorexia in situations involving acute inflammation. Specifically, we evaluated whether elevations of body temperature could account for the reduced food intake after induction of experimental colitis [via intrarectal infusions of trinitrobenzene sulfonic acid (TNB)] or injection of 100 micrograms/kg lipopolysaccharide (LPS). Temperature was monitored telemetrically in rats via implanted temperature transmitters. TNB-treated rats demonstrated a 5-day anorexia that resulted specifically from a decrease in meal size. Although TNB-treated rats were hypothermic on the day of treatment, no other body temperature changes were noted. LPS reduced food intake and elevated temperature, but these two effects were uncorrelated temporally. Although these results do not identify the mechanisms of anorexia, the findings indicate clearly that the anorexia associated with the acute inflammatory response is not secondary to fever.