Salicylate, tryptophan, and tyrosine hypothermia

The intraperitoneal administration of sodium salicylate, L-tryptophan, and tyrosine resulted in significant hypothermia when rats were exposed to a 4degree C ambient temperature. Salicylate and tryptophan increased plasma levels of nonprotein-bound tryptophan while total and bound tryptophan were reduced in salicylate-treated rats. Tryptophan concentrations were unaffected by tyrosine administration. Concomitant with increases in free plasma tryptophan, there occurred significant rises in brain levels of tryptophan in both groups of rats, while brain tyrosine levels were increased in those rats receiving tyrosine. Similarly, significant increments in hypothalamic serotonin levels in rats receiving salicylate or L-tryptophan and increases in hypothalamic norepinephrine in tyrosine-treated rats seem to reflect the increased availability of tryptophan and tyrosine for monamine synthesis. However, alternative mechanisms of hypothermiaseem to be operative since oxygen consumption studies demonstrate dissimilar results for tryptophan and salicylate administration.