Compound of the formula: (I) [wherein each of X.sup.1, X.sup.2 and X.sup.3 independently represents N or CH, W represents the formula (II):(II) or the formula (III):(III) and Y represents a group of the formula (IV):(IV)], or a pharmacologically acceptable salt thereof. This compound exhibits histamine receptor H3 antagonist or inverse agonist activity and is useful of the treatment and/or prevention of obesity, diabetes, hormonal secretion abnormality, sleep, disorder, etc. ##STR00001##