Imbutamine (4-(1H-imidazol-4-yl) butanamine) is a potent histamine H3 (H3R) and H4 receptor (H4R) agonist (EC50 values: 3 and 66nM, respectively). Aiming at improved selectivity for the H4R, the imidazole ring in imbutamine was methyl-substituted or replaced by various differently substituted heterocycles (1, 2, 3-triazoles, 1, 2, 4-triazoles, pyridines, pyrimidines) as potential bioisosteres. Investigations in [35S] GTPgS binding assays using ...