Table 1 Comparison of Binding Affinities at Opioid Receptors of N-Methylmorphinans 1–4 and Their N-Phenethyl Analogues 1a–4a.

From: N-Phenethyl Substitution in 14-Methoxy-N-methylmorphinan-6-ones Turns Selective µ Opioid Receptor Ligands into Dual µ/δ Opioid Receptor Agonists

Compound

Ki (nM)a

µOR

δOR

κOR

Ki ratio  δOR/µOR

Ki ratio κOR/µOR

Morphine (1)

3.35 ± 0.30

195 ± 26

96.4 ± 0.5

58

29

1a

0.25 ± 0.09***

24.5 ± 8.7*

93.5 ± 2.9

98

374

Oxymorphone (2)

1.41 ± 0.30

79.1 ± 9.3

32.6 ± 9.8

56

23

2a

0.12 ± 0.07*

10.7 ± 5.1*

42.2 ± 7.3

89

352

14-OMO (3)

0.27 ± 0.09

9.08 ± 0.31

10.3 ± 1.8

34

38

3a

0.19 ± 0.02

1.81 ± 0.68***

15.8 ± 8.8

9.5

83

14-MM (4)

0.25 ± 0.04

18.6 ± 0.98

12.8 ± 1.5

74

51

4a

0.24 ± 0.03

1.45 ± 0.31***

35.3 ± 5.5**

6.0

147

  1. aDetermined in competition binding assays using membranes from CHO cells stably expressing the human opioid receptors. Values represent the mean ± SEM (n = 3–4). *P < 0.05, **P < 0.01 and ***P < 0.001 for N-methylmorphinans vs. respective N-phenethyl analogues (unpaired t-test).
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