Table 1.
Receptor Binding Affinities and Functional Bioactivities of Compounds 1–6.
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Receptor affinity a (nM) | Selectivity | Functional bioactivity (nM) | ||||||
Comp. | Structure | R | Kiδ | Kiμ | Kiμ/Kiδ | MVD (IC50)b | MVD (p A2)c | GPI (IC50)b |
Ref. | H-Dmt-Tic-NH-CH2-Bid | ![]() |
0.035d | 0.50d | 14d | 0.94±0.21 | 35.5±7.3 | |
1 | H-Dmt-Tic-NH-CH2-Boa |
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0.283±0.048 (3) | 1.42±0.25 (6) | 5.0 | 9.42 | 169.9±32.2 | |
2 | H-Dmt-Tic-NH-CH2-Bta |
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0.145±0.018 (3) | 1.06±0.11 (4) | 7.3 | 9.37 | 129.1±21.5 | |
3 | H-Dmt-Tic-NH-CH2-Indl |
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0.066±0.013 (3) | 0.7±0.18 (4) | 10.6 | 9.45 | 208.9±48.1 | |
4 | H-Dmt-Tic-NH-CH2-Indn |
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0.199±0.032 (3) | 0.16±0.019 (4) | 1.2# | 129.0±23.9 | 28.41±1.74 | |
5 | H-Dmt-Tic-NH-CH2-ImidPh |
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0.443±0.13 (3) | 6.74±0.98 (5) | 15 | 9.40 | 153.5±10.4 | |
6 | H-Dmt-Tic-NH-CH2-Imid |
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0.114±0.017 (4) | 1.18±0.12 (6) | 10 | 3.63±0.52 | 111.3±37.8 |
μ selectivity Kiδ/ Kiμ.
The Ki values (nM) were determined according to Cheng and Prusoff.20 The mean ± SE with n repetitions in parenthesis is based on independent duplicate binding assays with five to eight peptide doses using several different synaptosomal preparations.
Agonist activity was expressed as IC50 obtained from dose-response curves. These values represents the mean ± SE for at least four tissue samples. DPDPE and PL-017 were the internal standards for MVD (δ-opioid receptor bioactivity) and GPI (μ-opioid receptor bioactivity) tissue preparation, respectively.
The pA2 values of opioid antagonists against the agonists (deltorphin II and endomorphin-2) were determined by the method of Kosterlitz and Watt.21
Data taken from Balboni et al.4