A novel nitrogenous fused bicyclic compound represented by the following general formula [1] or a pharmacologically acceptable salt of the compound. They have excellent SK channel blocking activity and are useful as a medicine. [I] (In the formula, R.sup.0 represents hydrogen, halogeno, etc.; R.sup.1 represents a group represented by the formula (a) or (b); A represents a group represented by the formula (X) or (Y); D.sup.1, D.sup.2 and D.sup.3 each represents N or CH; R.sup.2 represents halogeno or optionally halogenated lower alkyl, etc.; R.sup.3 represents hydrogen or lower alkyl; and Q represents lower alkylene.)