Use of Calculated Cation-π Binding Energies to Predict Relative Strengths of Nicotinic Acetylcholine Receptor Agonists

doi: 10.1021/cb800189y Agonists and antagonists of the nicotinic acetylcholine receptor (nAChR) are used to treat nicotine addiction, neuromuscular disorders, and neurological diseases. In designing small molecule therapeutics with the nAChR as a target, it is useful to identify chemical parameters that correlate with ability to activate the receptor. Previous studies have shown that cation-π interactions at the transmitter binding sites of the nAChR are important for receptor activation by strong agonists such as acetylcholine. We hypothesized that a calculated estimate of cation-π binding ability could be used to predict the efficiency for channel opening (i.e., the gating efficiency) associated with activation of the acetylcholine receptor by a series of structurally related organic cations. We demonstrate that the calculated cation-π energy is strongly correlated with gating efficiency but only weakly correlated with closed-state binding affinity. Our results suggest that cation-π interactions contribute significantly to the open-state affinity of these cations and that the calculated cation-π energy will be a useful parameter for designing nAChR agonists and antagonists.