The ability of various Gi/o α-subunit mutants to restore the superactivation of adenylyl cyclase activity after chronic DPDPE and PTX treatment N2A cells were infected with various adenovirus and treated with DPDPE and PTX chronically as described under Materials and Methods. The superactivation of adenylyl cyclase in these cells was then measured in the presence of various concentrations of naloxone. The values represent the average naloxone concentrations needed to induce 50% maximal superactivation ± S.D. from four separate experiments. Values in parentheses represent the maximal agonist-induced increase in adenylyl cyclase activity after long-term DPDPE treatment.
| EC50 | ||
|---|---|---|
| –PTX | +PTX | |
| nM | ||
| + Adeno-GFP (Control) | 2.0 ± 0.1 | N.E. |
| (215 ± 12) | ||
| + Adeno-Gαi2-Leu | 1.2 ± 0.2 | 2.5 ± 0.2 |
| (204 ± 14) | (155 ± 6) | |
| + Adeno-Gαi3-Leu | 0.4 ± 0.1 | N.E. |
| (200 ± 7) | ||
| + Adeno-Gαo-Leu | 0.9 ± 0.1 | N.E. |
| (230 ± 11) | ||
N.E., no excitation when naloxone ≤10-4 M