Table 2.
Operational parameters (estimates ± standard errors) for the G protein-dependent pathway.
| Em | n | Log (KA) | Log (τ) | Log(τ/KA) | |
|---|---|---|---|---|---|
| Morphine | 98.33 ± 1.41 | 1.04 ± 0.05 | −5.96 ± 0.11 | 2.12 ± 0.12 | 8.08 ± 0.04 |
| Fentanyl | 93.99 ± 1.01 | 1.22 ± 0.08 | −7.74 ± 0.10 | 2.23 ± 0.11 | 9.97 ± 0.05 |
| TRV130 | 98.15 ± 1.44 | 0.90 ± 0.04 | −7.63 ± 0.07 | 1.82 ± 0.09 | 9.45 ± 0.05 |
| Endomorphine-2 | 96.64 ± 2.12 | 1.02 ± 0.07 | −7.38 ± 0.17 | 1.97 ± 0.20 | 9.35 ± 0.07 |
| Buprenorphine | 96.75 | 0.98 ± 0.21 | −9.35 ± 0.23 | 0.85 ± 0.20 | 10.20 ± 0.10 |
Data obtained from concentration-response curves of µ-opioid agonists in presence of various concentrations of the irreversible antagonist β-FNX analyzed with the operational model of agonism (Fig. 3). Parameter estimates and standard errors of operational parameters Em, n, log(KA) and log(τ) were produced by global fitting. Common Em, n and KA parameters were shared between curves whereas a τ parameter was defined for each β-FNX concentration-dependent curve. In the Table, log(τ) for β-FNX concentration equal to 0 is shown. For buprenorphine, the fitting did not converge when Em was included as a free parameter; thus, we set Em equal to the mean of the values obtained for the other ligands (96.75) and kept it fixed as such in the fitting process. Log (τ/KA) values and their standard errors were calculated from estimated τ and KA parameters (see Parameter estimation in Methods).