Table 2.
Competition of [3H]DAMGO binding in hMOR-1 and hMOR-1i cells membranes
| Ki value (nM) | ||
|---|---|---|
| Ligand | hMOR-1 | hMOR-1i |
| Morphine | 0.8 ± 0.2 | 1.0 ± 0.1 |
| M6G | 2.5 ± 0.3 | 2.7 ± 0.2 |
| DADLE | 6.6 ± 1.1 | 6.2 ± 1.3 |
| DSLET | 4.9 ± 0.7 | 6.6 ± 1.5 |
| β-Endorphin | 1.4 ± 0.2 | 1.6 ± 0.2 |
| Dynorphin A | 9.3 ± 1.1 | 13.1 ± 2.0 |
| Methadone | 7.7 ± 0.2 | 11.2 ± 5.0 |
| Nalorphine | 1.1 ± 0.2 | 1.5 ± 0.3 |
| Buprenorphine | 1.8 ± 0.04 | 2.0 ± 0.2 |
| Naloxone | 0.6 ± 0.1 | 0.7 ± 0.2 |
| U50,488H | > 500 | > 500 |
| DPDPE | > 500 | > 500 |
Competition studies were performed with at least four concentrations of the indicated drugs against [3H]DAMGO binding in membranes from CHO cells stably transfected with the indicated cDNA clones, as described in Materials and Methods. IC50 values were determined by non-linear regression analysis and converted to Ki values (Cheng and Prusoff 1973). The results are the means ± SEM of at least three independent determinations.