Compounds represented by the general formula (I) ##STR00001## wherein Ar.sup.1 represents an aryl or heteroaryl which may be substituted; n represents 0 or 1; T, U, V and W each independently represent a nitrogen atom or a methine group which may have a substituent selected from the group consisting of halogen, lower alkyl, hydroxy and lower alkoxy, wherein at least two of which represent said methine group; X represents methine, hydroxy substituted methine or nitrogen atom; Y represents an imino which may be substituted with lower alkyl, or oxygen; and a salt, ester or N-oxide derivative thereof. The compounds exhibit NPY antagonistic activities and are useful as agents for the treatment of various diseases related to NPY, for example, cardiovascular disorders, central nervous system disorders, metabolic diseases, sexual and reproductive dysfunctions, gastro-intestinal disorders, respiratory disorders, inflammation or glaucoma, and the like.