YQA14: a novel dopamine D3 receptor antagonist that inhibits cocaine self-administration in rats and mice, but not in D3 receptor-knockout mice

ABSTRACT The dopamine (DA) D3 receptor is posited to be importantly involved in drug reward and addiction, and D3 receptor antagonists have shown extraordinary promise as potential anti‐addiction pharmacotherapeutic agents in animal models of drug addiction. SB‐277011A is the best characterized D3 receptor antagonist in such models. However, the potential use of SB‐277011A in humans is precluded by pharmacokinetic and toxicity problems. We here report a novel D3 receptor antagonist YQA14 that shows similar pharmacological properties as SB‐277011A. In vitro receptor binding assays suggest that YQA14 has two binding sites on human cloned D3 receptors with Ki‐High (0.68 × 10−4 nM) and Ki‐Low (2.11 nM), and displays > 150‐fold selectivity for D3 over D2 receptors and > 1000‐fold selectivity for D3 over other DA receptors. Systemic administration of YQA14 (6.25–25 mg/kg) or SB‐277011A (12.5–25 mg/kg) significantly and dose‐dependently reduced intravenous cocaine self‐administration under both low fixed‐ratio and progressive‐ratio reinforcement conditions in rats, while failing to alter oral sucrose self‐administration and locomotor activity, suggesting a selective inhibition of drug reward. However, when the drug dose was increased to 50 mg/kg, YQA14 and SB‐277011A significantly inhibited basal and cocaine‐enhanced locomotion in rats. Finally, both D3 antagonists dose‐dependently inhibited intravenous cocaine self‐administration in wild‐type mice, but not in D3 receptor‐knockout mice, suggesting that their action is mediated by D3 receptor blockade. These findings suggest that YQA14 has a similar anti‐addiction profile as SB‐277011A, and deserves further study and development.