Potencies and efficacies of various ligands for stimulating [35S]GTPγS binding
| Drug | n | EC50 | % Maximal Stimulation |
|---|---|---|---|
| nM | |||
| Etorphine | 11 | 0.973 ± 0.195 | 100 |
| Morphine | 6 | 36.3 ± 7.1 | 82 ± 23-a |
| Fentanyl | 8 | 59.7 ± 11.1 | 77 ± 23-a |
| RTI-1a | 4 | 1.01 ± 0.25 | 103 ± 6 |
| RTI-1b | 5 | 4.46 ± 0.49 | 105 ± 7 |
| RTI-1c | 8 | ND | 13 ± 43-a |
| RTI-1d | 8 | ND | 8 ± 23-a |
| Buprenorphine | 8 | ND | 21 ± 33-a |
Measurement of the ability of various ligands to stimulate [35S]GTPγS binding was performed as described inExperimental Procedures. The maximal amount of stimulation caused by each ligand is expressed as a percentage of the maximal amount of stimulation caused by etorphine. Curves were fitted to a standard four-parametric logistic equation with SigmaPlot (SPSS Inc., Chicago, IL). Results for RTI-1c, RTI-1d, and buprenorphine were based on treatment with 10 μM of each drug. Values are means ± S.E.
ND, not determined.
↵3-a Significantly less than etorphine-induced stimulation,P < .05 by Student's t test.