δ Opioidmimetic Antagonists: Prototypes for Designing a New Generation of Ultraselective Opioid Peptides

Table 3 Receptor binding characteristics to κ ₂ receptor sites

Peptide	K_i^δ(μM)	K_i^δ/K_i^κ	K_i^μ/K_i^κ
1. Dmt-Tic-OH	23,806 ± 2,697 (3)	0.0000009	0.14
2. Dmt-Tic-NH₂	1,943 ± 113 (3)	0.0006	0.14
3. Dmt-d-Tic-OH	9,863 ± 2,621 (3)	0.0014	0.02
4. Dmt-d-Tic-NH₂	5,291 ± 105 (3)	0.011	0.0007
5. Dmt-Tic-CH₂OH	1,107 ± 158 (4)	0.0004	0.14
6. Tyr-Tic-OH	>60,000	−	—
11. Dmt-Tic-Ala-OH	>50,000 (3)	<0.000006	0.12
12. Dmt-Tic-Ala-NH₂	8,694 ± 1,254 (5)	0.000028	0.005
13. Dmt-d-Tic-Ala-OH	9,752 ± 2,418 (3)	0.009	0.008
14. Dmt-d-Tic-Ala-NH₂	7,087 ± 2,181 (3)	0.0007	0.0008
15. Tyr-Tic-Ala-OH	>60,000	−	—
16. Tyr-Tic-Ala-NH₂	>60,000	−	—

K_i, affinity constant. Dynorphin A-(1-13)-OH (porcine) is included as an internal control. The κ selectivities relative to δ (K_i^δK_i^κ) and μ receptors (K_i^μ/K_i^κ) are from the binding data in Table 2. SEM is listed only for n = 3–5 as indicated by the number in the parenthesis.

ISSN: 1528-3658