Fig. 2.

Locomotor activating effects of opioids with differing MOR efficacy. (A) Effects of opioids administered alone. (B) Effects of nalbuphine, NAQ and naltrexone administered as a pretreatment to 10 mg/kg morphine. Abscissae: Dose in mg/kg. Ordinates: Locomotor counts per 60 minutes. In general, all points show mean±S.E.M. for N = 12 mice, and filled symbols indicate a significant difference compared with vehicle within each drug as determined by repeated-measures one-way ANOVA followed by the Holm-Sidak post hoc test, P < 0.05. There were two exceptions. The dashed line to 3.2 mg/kg of buprenorphine indicates low sample size (N = 6) and a different cohort of mice for this dose, and the filled point indicates different from vehicle by unpaired t test. The dashed line at 100 mg/kg hydrocodone indicates low sample size (N = 6) but in the same cohort of mice for this dose, and the filled symbol indicates different from vehicle by paired t test. A different group of four male and female mice tested with a higher hydrocodone dose (320 mg/kg) all died, so further studies at this dose were not conducted, and these data are not included in the graph. Statistical results for Panel A are shown in Table 1. For Panel B, one-way ANOVA results were as follows. Nalbuphine: F(1.64, 18.02) = 14.42; P = 0.0003; NAQ: F(4.15, 45.68) = 8.67; P < 0.0001; naltrexone: F(2.59, 28.45) = 27.35; P < 0.0001.