Highly selective and high-affinity mu (μ) opioid receptor (MOR) antagonist in vitro and in vivo.
NAQ is a highly selective and high-affinity mu (μ) opioid receptor (MOR) antagonist with 241- & 48-fold selectivity over the delta (δ) and kappa (K) opioid receptor, respectively (MOR/DOR/KOR Ki = 0.55/132.5/26.45 nM) and little MOR agonist activity (Emax = 15.83% of th at of DAMGO by GTP[γS] binding using membrane from MOR-expressing cells). NAQ effectively antagonizes morphine antinociceptive effects in mice in vivo (warm-water tail immersion test AD50 = 0.45 mg/kg s.c. 5 min prior to 10 mg morphine/kg s.c.; no agonist efficacy up to 100 mg/kg).
