Allosteric potentiation of acetylcholine nicotinic receptors is considered to be one of the most promising approaches for the treatment of Alzheimer's disease. However, the exact localization of the allosteric binding site and the potentiation mechanism at the molecular level are presently unknown. We have performed the "blind docking" of three known allosteric modulators (galanthamine, codeine and eserine) with the Acetylcholine Binding Protein and models of human alpha7, alpha3beta4 and alpha4beta2 nicotinic receptors, created by homology modeling. Three putative binding sites were identified in the channel pore, each one showing different affinities for the ligands. One of these sites is localized opposite to the agonist binding site and is probably implicated in the potentiation process. On the basis of these results, a possible mechanism for nicotinic acetylcholine receptor (nAChRs) activation is proposed. The present findings may represent an important advance for understanding the allosteric modulation mechanism of nAChRs. [Figure: see text].

A new highly selective inhibitor of acetylcholinesterase (AChE) was discovered by high-throughput screening. Compound 1 was synthesized from a natural product, the N-3-isobutyrylcycloxobuxidine-F 2. A new extraction protocol of this compound is described. The hemisynthesis and optimization of 1 are reported. The analogs of 1 were tested in vitro for the inhibition of both cholinesterases (AChE and BuChE). These compounds selectively inhibited AChE. Extensive molecular docking studies were performed with 2 and AChE employing Discover Biosym software to rationalize the binding interaction. The results suggested that ligand 2 binds simultaneously to both catalytic and peripheral sites of AChE.