Effect of tryptophan and selected analogues on body temperatur of endotoxin-poisoned mice.

The effect of endotoxin on the body temperature of mice was studied in animals housed without bedding at an environmental temperature of 15 C. Rectal temperatures were measured during the initial 3 to 5 hr of exposure. Doses of endotoxin ranging from 0.01 to 1 ld(50), as determined for mice maintained at 25 C, produce a hypothermia in proportion to dose. Concurrent injection of tryptophan magnified this response in a dose-dependent manner. Cyproheptadine, an antiserotonin drug, antagonized both the hypothermia produced by serotonin alone, and the augmentation of hypothermia produced by tryptophan in endotoxin-poisoned mice. alpha-Methyltryptophan, an analogue of the amino acid that is known to induce tryptophan pyrrolase, also antagonized the increased hypothermia produced by tryptophan. These data support a previous suggestion that inhibition of tryptophan pyrrolase in endotoxin-poisoned mice has the effect of funneling injected tryptophan into the serotonin pathway.