Compounds represented by the general formula (I): ##STR00001## wherein Ar.sup.1 and Ar.sup.2 are each aryl or heteroaryl; R.sup.1 is lower cycloalkyl, --Ar.sup.3, or a group of the general formula (a), (b) or (c): ##STR00002## and R.sup.2 and R.sup.3 are each hydrogen, lower cycloalkyl, lower alkenyl, or optionally substituted lower alkyl (with the proviso that when R.sup.2 and R.sup.3 are simultaneously hydrogen, Ar.sup.1, Ar.sup.2 and R.sup.1 do not simultaneously represent unsubstituted phenyl). The compounds are useful as treating agents for various NPY-related diseases, for example, circulatory diseases including hypertension, kidney diseases, cardiac diseases, vasospasm and arteriosclerosis; central nervous system diseases including hyperphagia, depression, anxiety, convulsion, epilepsy, dementia, pain, alcohol dependence, and withdrawal symptoms due to abstinence from drugs; metabolic diseases including obesity, diabetes, hormonal disorders, hypercholesterolemia, and hyperlipidemia; sexual dysfunction and reproductive function disorders; digestive diseases including enterokinetic disorders; respiratory diseases; inflammation; or glaucoma.