Compounds of formula (A): wherein: W is a residue which imparts antagonistic and/or agonistic activity at histamine H3-receptors when attached to an imidazole ring in 4(5) position. R1 and R2 may be identical or different and represent each independentlya lower alkyl or cycloalkyl, or taken together with the nitrogen atom to which they are attached,a saturated nitrogen-containing ring (i) as defined,a non-aromatic unsaturated nitrogen-containing ring (ii) as defined,a morpholino group, ora N-substituted piperazino group as defined. Compounds (A) are useful for preparing medicaments acting as antagonists and/or agonists at the H 3 -receptors of histamine.