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. 2020 Mar 17;25(6):1370. doi: 10.3390/molecules25061370

Figure 2.

Figure 2

Dose-response curves featuring binding affinity of 14-methoxycodeine-6-O-sulfate (14-OMeC6SU) and codeine-6-O-sulfate (C6SU) to µ-opioid receptor (A), δ-opioid receptor (B) and κ-opioid receptor (C) compared to codeine and morphine in competition binding experiments performed in rat (A and B) and guinea pig (C) brain membrane homogenate. For control the unlabeled form of the applied radioligands are also indicated. All figures represent the specific binding of the corresponding radioligand (A: [3H]DAMGO, B: [3H]Ile5,6-deltorphin II [IleDelt II], C: [3H]U-69593) in percentage (means ± S.E.M.) normalized to total specific binding (100%) in the presence of increasing concentrations (0.1 nM–10 μM) of the indicated unlabeled ligands. Total specific binding was determined in the absence of the indicated unlabeled ligands and indicated with a dotted line. The Ki ± S.E.M. values are presented in Table 1.