5-Substituted Imidazole-4-acetic Acid Analogues: Synthesis, Modeling, and Pharmacological Characterization of a Series of Novel γ-Aminobutyric Acid<sub>C</sub> Receptor Agonists
作者:Christian Madsen、Anders A. Jensen、Tommy Liljefors、Uffe Kristiansen、Birgitte Nielsen、Camilla P. Hansen、Mogens Larsen、Bjarke Ebert、Benny Bang-Andersen、Povl Krogsgaard-Larsen、Bente Frølund
DOI:10.1021/jm070447j
日期:2007.8.1
A series of ring-substituted analogues of imidazole-4-acetic acid (IAA, 4), a partial agonist at both GABA(A) and GABA(C) receptors (GABA = gamma-aminobutyric acid), have been synthesized. The synthesized compounds 8a-1 have been evaluated as ligands for the alpha(1)beta(2)gamma(2S) GABA(A) receptors and the rho(1) GABA(C) receptors using the FLIPR membrane potential (FMP) assay and by electrophysiology techniques. None of the tested compounds displayed activity at the GABA(A) receptors at concentrations up to 1000 mu M. However, the 5-Me, 5-Ph, 5-p-Me-Ph, and 5-p-F-Ph IAA analogues, 8a,c,f,g, displayed full agonist activities at the rho(1) receptors in the FMP assay (EC50 in the range 22-420 mu M). Ligand-protein docking identified the Thr129 in the alpha(1) subunit and the corresponding Ser168 residue in rho(1) as determinants of the selectivity displayed by the 5-substituted IAA analogues. The fact that GABA, 4, and 8a displayed decreased agonist potencies at a rho(1)Ser168Thr mutant compared to the WT rho(1) receptor strongly supported this hypothesis. However, in contrast to GABA and 4, which exhibited increased agonist potencies at a alpha(1)(Thr129Ser)beta(2)gamma(2) mutant compared to WT GABA(A) receptor, the data obtained for 8a at the WT and mutant receptors were nonconclusive.