The atomic determination of the acetylcholine binding protein (AChBP), a molluscan cholinergic protein, homologous to the amino-terminal extracellular domain of nicotinic receptors (nAChRs), offers opportunities for the modeling of the acetylcholine binding site and its ligands. Recently, we constructed three-dimensional models of the N-terminal part of nAChR and docked in the putative ligand-binding pocket, different agonists (acetylcholine, nicotine and epibatidine) and antagonist (snake alpha-bungarotoxin). These hypothetical docking models offer a structural basis for rational design of drugs differentially binding to resting and active (or desensitized) conformations of the receptor site. These models thus pave the way to investigate, at the molecular level, the exciting challenge of the fast ion channel gating mechanisms by nicotinic agonists.