Table 1.
Morphine-induced antinociceptive tolerance (%MPE) in the tail-flick (mean ± SEM, n = 7–9 per group) and hot-plate (mean ± SEM, n = 3–4 per group) assays
| Assay | Mouse | Repeated saline ED50 (95% CI) |
Repeated morphine ED50 (95% CI) |
Sig. | Potency ratio (95% CI) |
|---|---|---|---|---|---|
| Tail flick | Tat(−) | 8.6 (7.0–10.5) | 26.6 (20.3–34.8) | * | 3.2 (2.3–4.4)a |
| Tat(+) | 7.8 (6.2–9.8) | 91.3 (60.7–137.4)1 | * | 6.7 (4.6–10.8)a§ | |
| Hot plate | Tat(−) | 6.1 (4.3–8.7) | 14.5 (8.1–26.1) | n.s. | 2.7 (0.5–8.7) |
| Tat(+) | 5.4 (4.2–7.0) | 23.0 (11.4–46.3) | * | 4.4 (0.7–28.9) |
ED50 values (mg/kg) and potency ratio values are derived from acute cumulative dose-response curves obtained for repeated short-term saline- and morphine-exposed mice.; n.s. not significant; *p < 0.05 saline vs. corresponding morphine group; ap < 0.05; §Indicates significance from Tat(−) in the tail-flick assay based on non-overlapping 95% CI. Note, as the potency ratio of 6.7 is based on an estimated ED50 value caution should be exercised when interpreting the data. CI confidence interval
1Estimated ED50