Treatment | EC50 | Maximal stimulation |
---|---|---|
nm | % over control | |
Control | 28 ± 6 | 367 ± 21 |
DAMGO | 209 ± 14 | 149 ± 10 |
Morphine | 103 ± 10 | 286 ± 16 |
Butorphanol | 58 ± 18 | 325 ± 9 |
Etorphine | >600 | 58 ± 7 |
β-Endorphin | 240 ± 12 | 205 ± 9 |
Confluent cells in medium were incubated with 10 μm of each agonist for 24 hr; then, cells were washed with PBS and collected, and membranes were prepared as described in Experimental Procedures. [GTPγ35S] binding to membranes was measured in the presence of DAMGO (1 nm to 10 μm) at 25° for 30 min. Data are expressed as percentage stimulation over that obtained in the absence of added DAMGO.
Values are mean ± standard error from four or five experiments.