Conformational analysis, pharmacophore identification, and comparative molecular field analysis of ligands for the neuromodulatory sigma 3 receptor.
Molecular modeling studies were carried out on a series of 1-phenyl-3-amino-1,2,3,4-tetrahydronaphthalenes (phenylaminotetralins, PATs), several PAT structural analogs, and various non-PAT ligands that demonstrate a range of affinities for a novel sigma 3 receptor linked to stimulation of tyrosine hydroxylase and dopamine synthesis in rodent brain. In an effort to develop a ligand-binding model for the sigma 3 receptor, a pharmacophore mapping program (DISCO) was used to identify structural features that are common to ligands that exhibit moderate to high binding affinity for sigma 3 sites. DISCO then was utilized to propose a common pharmacophoric region that included one low-energy conformation of each compound in the training set. The resulting alignment was utilized in a comparative molecular field analysis (CoMFA) study in an attempt to correlate the steric and electrostatic fields of the molecules with the respective binding affinities at the sigma 3 receptor. A suitably predictive model was obtained from the CoMFA analysis which will be employed in the development of additional PAT analogs that could potentially display high affinity and selectivity for the sigma 3 receptor. The excluded volumes which resulted from comparing molecular volumes of active and inactive compounds were visualized to examine the limits of steric tolerance imposed by the sigma 3 receptor.