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. 2003 Nov 12;23(32):10265–10273. doi: 10.1523/JNEUROSCI.23-32-10265.2003

Figure 1.

Figure 1.

Locomotor activity after acute morphine treatment. A, Basal locomotor activity in WT and βarr2-KO mice during a 1 hr habituation period (for time, F(11,1022) = 32.89, p < 0.0001; for genotype, F(1,93) = 8.26, p < 0.005; n = 46-49). B, Effects of an acute dose of morphine. Morphine (10 mg/kg, s.c.) was administered to wild-type (n = 8), heterozygotes (n = 8), and βarr2-KO (n = 8) mice after a 1 hr habituation period. Locomotor activity was assessed as the number of infrared beam breaks in 5 min intervals. The values were averaged across mice, and the means ± SEM are shown here. Morphine-induced locomotor activity in all three groups, yet the genotypes did not differ significantly at this dose (for genotype, F(23,483) = 27.94, p < 0.0001; for dose, F(2,21) = 2.62, p = 0.0965). C, Morphine dose-response curve for locomotor activity. The number of beam breaks was summed over the 120 min test period, and the mean ± SEM after morphine or saline (10 μl/g, s.c.) administration is presented. The sum of the beam breaks in B is included in this graph, representing the 10 mg/kg dose. Overall, morphine produced greater increases in locomotor activity in WT mice than in the βarr2-KO mice (for genotype, F(1,95) = 70.22, p < 0.001; for dose, F(4,95) = 36.07, p<0.0001; n = 8-16). Bonferroni post hoc analysis revealed significant differences between the genotypes at the doses of 5, 20, and 40 mg/kg subcutaneous morphine (WT vs KO; *p < 0.05; **p < 0.001).