Table 1.
Ligand-binding properties of κ–δ heterodimer
| Ligand | Ki (nM) | ||
|---|---|---|---|
| κ | δ | κ–δ | |
| Agonists | |||
| U69593 | 14.4 ± 0.2 | >1,000 | >1,000 |
| DPDPE | >1,000 | 21.8 ± 2.1 | >1,000 |
| Dynorphin A | 1.3 ± 0.41 | 56.8 ± 0.3 | 5.6 ± 0.3 |
| EKC | 5.7 ± 0.79 | 105 ± 1.2 | 2.6 ± 0.2 |
| Etorphine | 1.5 ± 0.73 | 7.9 ± 0.03 | 7.0 ± 0.3 |
| Bremazocine | 0.4 ± 0.11 | 7.5 ± 0.03 | 1.2 ± 0.1 |
| Antagonists | |||
| Norbinaltorphimine | 4.9 ± 0.3 | 31.8 ± 1.2 | 126 ± 9.6 |
| TIPPΨ | >1,000 | 0.28 ± 0.6 | >1,000 |
| BNTX | 172 ± 19 | 5.2 ± 0.6 | 98 ± 19 |
| Naltrindole | 44.3 ± 1.1 | 1.0 ± 0.21 | 44 ± 1.1 |
| Naloxone | 14.9 ± 3.4 | 43.4 ± 0.3 | 7.5 ± 0.4 |
| Diprenorphine | 0.71 ± 0.27 | 1.43 ± 1.1 | 0.3 ± 0.1 |
| Combination of ligands | |||
| U69593 (+10 µM DPDPE) | 14.4 ± 0.4 | – | 9.2 ± 1.4 |
| DPDPE (+10 µM U69593) | – | 24.8 ± 1.6 | 20.0 ± 1.3 |
| Norbinaltorphimine (+10 µM TIPPΨ) | – | – | 0.02 ± 0.003 |
| U69593 (+10 µM TIPPΨ) | – | – | >1,000 |
Ligand affinities were determined by competition assays using 3H-diprenorphine as described. Mean ± s.e.m. (n = 3–4). BNTX, 7-benzylidenenaltrexone; EKC, ethylketocyclazocine;–, not done.