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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

From: Escalating morphine dosing in HIV-1 Tat transgenic mice with sustained Tat exposure reveals an allostatic shift in neuroinflammatory regulation accompanied by increased neuroprotective non-endocannabinoid lipid signaling molecules and amino acids

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)
  1. 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
  2. 1Estimated ED50