The neuroactivities of kynurenines — the endogenous metabolites of tryptophan have been studied in our laboratory since the begin of 70-ies (ref. see Lapin, 1989). Initially, the major subjects of our pharmacological experiments on mice and rats were the interaction with monoamines (Lapin, 1972–1976) and the convulsant effect of quinolinic acid (QUIN) and kynurenine (KYN) as well as their excitatory action (Lapin, 1978a, 1978b, 1980, 1981) and the anticonvulsant effect of kynurenic (KYNA), picolinic and xanthurenic acids (Lapin, 1985, Lapin et al., 1986)). Later several experimental evidences have promted the studies of the relevance of kynurenines to anxiety (ref. see — Lapin, 1989):