Major metabolites of tryptophan: kynurenine (K), 3-hydroxykynurenine (3-HK), 3-hydroxyanthranilie (3-ttAA), anthranilic (AA), picolinic (PA), quinolinic (QA) and nicotinic (NA) acids injected i.p. or s.c. were studied in rats and mice. In rats 3-HK, 3-HAA, AA and NA in doses of 5--20 mg/kg diminished 5-hydroxytryptophan-produced head-twitches but did not affect hypothermia. PA and NA also diminished tryptophan-produced head-twitches. In mice pretreated with nialamide the metabolites tested (3-ttK and QA were not tested in a wide dose range) decreased tryptamine-produced head twitches and increased hyperthermia. K, 3-ttAA, AA, PA and NA prolonged the latency of oxotremorine tremor in mice and did not influence hypothermia, salivation or diarrhoea.
Antiserotonin and antitryptamine activity of metabolites of kynurenine could possibly enhance the deficiency of brain serotonin and tryptamine which occurs as a result of the "tryptophan drain" under emotional stress when corticosteroids activate liver tryptophan pyrrolase. Diminution of central serotoninergic and cholinergie processes by metabolites of K may be responsible for the shift of a balance between tropho-and ergotropic systems towards predominance of the ergotropic system.