Screening Of Novel Dopamine D 3 Receptor Antagonist And The Pharmacological Evaluation

Objective: Dopamine D₃ receptors (D₃R) are preferentially localized in the mesolimbic DA system in rodent and human brain which are related to drug addiction. In recent years, most studies have focused on the role of D3R in drug dependence, and researcheres gradually paid much attention to the development of new anti-relapse drugs targeted D₃R. More than 80 kinds of high selective D₃R ligand have been found, some of which have been in clinical trail. However, they have severe adverse effects. In our present study, a series of new compounds have been synthesized and screened to find highly selective D3 receptor antagonists, and the efficency on psychological dependence models have been evaluated.Methods: First we transfect the recombinant DNA of GRCRs stably or transiently into CHO or HEK293 cells to construct 32 cell lines expressing different kinds of GRCRs. Radioliand receptor binding assays were used to evaluate the inhibition of compounds at hD3R compared with hD2R for primary screening.[35_S]GTPγS filtration assay was used to determine the activity of ligand to Gi/Gs protein coupled receptors; characterization of the changes in [Ca²⁺]i in the cells stably expressing Gq protein coupled receptors was measured using the Ca⁽2+0 indicator fluo-3.Preliminary pharmacokinetics properties including the bioavailability and the stability in human liver microsome of the compounds have been studied. The effect of the compounds on the expression of morphine induced behavior sensitization.Results:1 32 cell lines expressed different GPCRs have been set up.2 Y-QA31 showed high affinity for hD₃R and displays 2690-fold selectivity for D3 over D2 receptors, which were better than SB-277011A.3 Y-QA31 dispalys more than 1000-fold selectivity for D3 over other DA receptors and other 28 GPCR, with moderate affinity (about 100-fold) for 5-HT_1A receptor (IC₅₀=3.5±0.2 nM),α1A adrenoceptor (IC₅₀=86.3±1.2 nM),α1B adrenoceptor (IC₅₀=170.8±3.2 nM) and H1 histamine receptor (IC₅₀=568.5±0.1 nM).4 Functional assays showed Y-QA31 (10^-10-10^-5M) did not stimulate D3R and D2R; partial stimulate D2R ; but antagonized the stimulation effect of quinpirole in a dose dependent manner.5 Y-QA31 inhibited [(35)^S] GTPγS binding assay on 8-OH-DPAT stimulated G protein activation in rat hippocampal membranes. Y-QA31 antagonized NA-stimulated effect on humanα1A adrenoceptor; and moderate antagonize NA-stimulated effect on humanα1B adrenoceptor, as well as histamine stimulated effect on H1 histamine receptor.6 Pharmacokinetics studies showed that bioavailability of Y-QA31 is 44.48% and keep stable in rat liver microsome.7 Y-QA31 (3.125-12.5 mg·kg^-1) had no significient influence on mice locomotor acivity. However, Y-QA31 (6.25, 12.5 mg/kg, i.p.) inhibited the expression of morphine (5 mg/kg) induced behavior sensitization in a dose dependent manner.Conclusions: Y-QA31 is a novel seletive D3R antagonist,Y-QA31 inhibited morphine dependence significantly. Therefore, Y-QA31 is promising to be a leading compound for the prevention and therapy of drug dependence. The effect of Y-QA31 on drug dependence still needs forther study.