Effect on (−)U50,488H-stimulated [35S]GTPγS binding and [3H]diprenorphine binding to the κ receptor of 4-h pretreatment with 0.1 μM (−)U50,488H, 1 μM (+)U50,488H, 1 μM naloxone and 0.1 μM (−)U50,488H + 1 μM naloxone, and 4 h of 0.1 μM (−)U50,488H followed by 24-h recovery
| [35S]GTPγS binding | [3H]Diprenorphine binding | |||
|---|---|---|---|---|
| EC50 | Maximal binding | Kd | Bmax | |
| nM | fmol/mg protein | nM | fmol/mg protein | |
| Control | 3.8 ± 0.5 | 191 ± 3 | 0.16 ± 0.02 | 1217 ± 48 |
| (−)U50,488H, 0.1 μM | 9.2 ± 1.34-a | 109 ± 64-a | 0.20 ± 0.01 | 858 ± 294-a |
| (+)U50,488H, 1 μM | 2.7 ± 0.7 | 204 ± 6 | 0.14 ± 0.01 | 1158 ± 21 |
| Naloxone, 10 μM | 3.2 ± 1.2 | 193 ± 10 | 0.21 ± 0.02 | 1166 ± 36 |
| (−)U50,488H, 0.1 μM + Naloxone, 10 μM | 3.3 ± 1.1 | 179 ± 7 | 0.23 ± 0.01 | 1283 ± 36 |
| (−)U50,488H, 0.1 μM + 24-h recovery | 3.4 ± 1.3 | 189 ± 8 | 0.24 ± 0.03 | 1282 ± 25 |
CHO-hkor cells were subjected to various treatments as indicated and washed; the (−)U50,488H-induced increases in [35S]GTPγS binding and [3H]diprenorphine binding to the receptor were conducted as described under “Materials and Methods.” Each datum represents mean ± S.E.M. of three to six experiments. Data were analyzed by analysis of variance followed by the SheffeF-test.
↵4-a P < .05 compared with the control.