The efficient preparation and pharmacological characterization of different families of (bis)guanidine and
(bis)2-aminoimidazoline derivatives (“twin” and “half” molecules) as potential α2-adrenoceptor antagonists
for the treatment of depression is presented. The affinity toward the α2-adrenoceptor of all the compounds
prepared was measured in vitro in human brain tissue. Additionally, the activity as agonist or antagonist of
those compounds with a pK
i larger than 7 was determined in functional [35S]GTPγS binding assays in
human brain tissue. Finally, the activity of the most promising compounds was confirmed by means of in
vivo microdialysis experiments in rats. Compounds 1, 2b, 3b, 12b, 13b, 17b, 18b, 22b, 25b, 26b, 28b, and
30 showed a good affinity toward the α2-ARs. In general, the 2-aminoimidazoline derivatives displayed
higher affinities than their guanidine analogues. Finally and most importantly, compounds 18b and 26b
showed antagonistic properties over α2-ARs not only in vitro [35S]GTPγS binding but also in vivo
microdialysis experiments. Moreover, both compounds have shown to be able to cross the blood−brain
barrier and, therefore, they can be considered as potential antidepressants.