A method for treating a central nervous system disorder, which involves administering to a patient in need a therapeutically effective amount of a compound of formula (I): wherein Ar1 represents an aryl or heteroaryl which may be substituted, the substituent being selected from the group consisting of halogen, nitro, lower alkyl, halo(lower) alkyl, hydroxy(lower) alkyl, cyclo(lower) alkyl, lower alkenyl, lower alkoxy, halo(lower) alkoxy, lower alkylthio, carboxyl, lower alkanoyl, lower alkoxycarbonyl, lower alkylene optionally substituted with oxo, and a group represented by the formula —Q—Ar2; Ar2 represents an aryl or heteroaryl which may be substituted, the substituent being selected from the group consisting of halogen, cyano, lower alkyl, halo(lower) alkyl, hydroxy(lower) alkyl, hydroxy, lower alkoxy, halo(lower) alkoxy, lower alkylamino, di-lower alkylamino, lower alkanoyl and aryl: n represents 0 or 1; Q represents a single bond or carbonyl; 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; Y represents an imino which may be substituted with lower alkyl, or oxygen; or a salt or ester thereof