Provided is a kynurenine production inhibitor comprising a nitrogen-containing heterocyclic compound represented by formula (I): (wherein R 50 and R 51 may be the same or different and each represent a hydrogen atom or the like, G 1 and G 2 may be the same or different and each represent a nitrogen atom or the like, X represents formula (III): (wherein m 1 and m 2 may be the same or different and each represent an integer of 0 or 1, Y represents an oxygen atom or the like, and R 6 and R 7 may be the same or different and each represent a hydrogen atom or the like), R 1 represents optionally substituted lower alkyl or the like, R 2 represents a hydrogen atom or the like, and R 3 represents optionally substituted lower alkyl or the like), and the like.本發明提供一種犬尿胺酸產生抑制劑等，其係含有由下列式(I)所表示之含氮雜環化合物：(式中，R50及R51係相同或不同，而表示氫原子等；G1及G2係相同或不同，而表示氮原子等；X表示上列式(III)(式中，m1及m2係相同或不同，而表示0或1之整數；Y表示氧原子等；R6及R7係相同或不同，而表示氫原子等)；R1表示可具有取代基之低級烷基等，R2表示氫原子等，R3表示可具有取代基之低級烷基等)。
