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. Author manuscript; available in PMC: 2011 Feb 1.
Published in final edited form as: Chem Biol Drug Des. 2009 Dec 17;75(2):182–188. doi: 10.1111/j.1747-0285.2009.00919.x

Table 2.

Opioid receptor binding data of N-methylated cyclic enkephalin analogues

Ki (nM)a
 Ki ratio
Compound μ b δ b κ c μ/δ/κ
1 0.496 ± 0.037 2.29 ± 0.09 0.447 ± 0.070 1/5/1
2 0.354 ± 0.038 2.36 ± 0.48 0.855 ± 0.087 1/7/2
3 0.504 ± 0.039 0.525 ± 0.059 1.01 ± 0.06 1/1/2
4 0.586 ± 0.011 0.776 ± 0.050 0.894 ± 0.126 1/1/2
5 0.876 ± 0.059 6.07 ± 0.39 1.42 ± 0.16 1/7/2
6 0.641 ± 0.010 1.79 ± 0.03 0.875 ± 0.015 1/3/1
7 0.412 ± 0.035 0.202 ± 0.005 0.602 ± 0.152 1/1/1
8 0.282 ± 0.041 0.306 ± 0.011 0.677 ± 0.055 1/1/2
9 14.4 ± 1.0 35.9 ± 3.5 29.5 ± 1.4 1/2/2
a

Values represent means of 3-6 determinations ± SEM.

b

Displacement of [3H]DAMGO (μ-selective) and [3H]DSLET (δ-selective) from rat brain membrane binding sites.

c

Displacement of [3H]U69,593 (κ-selective) from guinea pig brain membrane binding sites.