This work presents the design and synthesis of a series of novel 2-benzylquinuclidine derivatives, comprising 12 methiodide and 11 hydrochloride salts, and their structural and pharmacological characterization at the human (h) alpha 7 and alpha 4 beta 2 nicotinic receptors (nAChRs). The antagonistic potency of these compounds was tested by Ca2+ influx assays on cells expressing the h alpha 7 or h alpha 4 beta 2 nAChR subtype. To determine the inhibitory mechanisms, additional radioligand binding experiments were performed. The results indicate that the methiodides present the highest affinities for the flea nAChR agonist sites, while the same compounds bind preferably to the h alpha 4 beta 2 nAChR ion channel domain. These results indicate that the methiodides are competitive antagonists of the h alpha 7 nAChR but noncompetitive antagonists of the h alpha 4 beta 2 subtype. Docking and molecular dynamics simulations showed that the methiodide derivative 8d binds to the h alpha 7 orthosteric binding sites by forming stable cation-pi interactions between the quaternized quinulinuim moiety and the aromatic box in the receptor, whereas compounds 7j and 8j block the h alpha 4 beta 2 AChR ion channel by interacting with a luminal domain formed between the serine (position 6') and valine (position 13') rings that overlaps the imipramine binding site. (C) 2013 Elsevier Ltd. All rights reserved.