TABLE 1.
ED50 values for μ-opioid agonists to produce antinociception in the assays of acid-stimulated stretching or acid-induced depression of ICSS
Data are presented as ED50 values with 95% confidence limits.
| Agonist | Acid-Stimulated Stretching | Acid-Depressed ICSS |
|---|---|---|
| mg/kg | ||
| 1.8% Lactic acid | ||
| Methadone | 0.272 (0.145–0.511) | 0.051 (0.030–0.085)a |
| Fentanyl | 0.008 (0.006–0.011) | 0.004 (0.003–0.006)a |
| Morphine | 0.171 (0.097–0.301) | 0.124 (0.070–0.218) |
| Hydrocodone | 0.343 (0.236–0.501) | 0.239 (0.161–0.355) |
| Buprenorphine | 0.002 (0.001–0.005) | 0.004 (0.002–0.008) |
| Nalbuphine | 0.217 (0.152–0.309) | 0.328 (0.130–0.826) |
| 5.6% Lactic acid | ||
| Methadone | Not tested | 0.51 (0.08–3.46) |
| Nalbuphine | Not tested | 4.90 (1.52–15.86)b |
a
Indicates significantly different from acid-stimulated stretching as indicated by nonoverlapping confidence limits.
b
Indicates significantly lower potency to block depression of ICSS by 5.6% than 1.8% lactic acid as indicated by nonoverlapping confidence limits.