Table 5. ED50 Values for Morphine and UMB 425 in the Tolerance Treatment Paradigmsa.
| morphine |
UMB
425 |
|||
|---|---|---|---|---|
| ED50 (mg/kg) | tolerance | shift | tolerance | shift |
| hot plate | 21.31 | 7.8 | 12.96 | 3.0 |
| tail-flick | 44.11 | 6.4 | 11.58 | 1.3 |
a
Summary of antinociceptive activity obtained for the tolerance paradigm for morphine and UMB 425 for the hot plate and tail-flick assays. Mice were treated with the ED90 dose of morphine (15 mg/kg, s.c.) or UMB 425 (15 mg/kg, s.c.) determined in the acute treatment paradigm, twice a day for 5 days. ED50 values for the tolerance paradigm were obtained during a dose–response challenge on Day 6 of treatment, whereby latencies were determined 30 min after drug administration (tolerance columns). The shifts represent fold-shifts in the ED50 determined in the acute vs tolerance treatment paradigms.