Figure 2.

Oxycodone-induced locomotion is absent in constitutive MOR KOs. A, Oxycodone (10 mg/kg, s.c.) induces hyperlocomotion in WT mice (WT) that is absent in mice lacking all MORs (KO) on the first (**p < 0.01 vs WT) and third (***p < 0.001 vs WT) days of three consecutive days of oxycodone. There was no difference between the effect of oxycodone in KO mice with that of saline in WT mice (p = 0.92). B, The intrasession data (shown here in 5-min timebins for the 60-min test) further show the lack of effect of oxycodone in KO mice on days 1 and 3 (p < 0.0001 vs WT at all timepoints for both days). WTs demonstrated a sensitization of this locomotor response (p < 0.01) from day 1 to day 3 that was absent in KOs. Refer to Table 3 for statistical analyses. All data are shown as mean ± SEM, and the individual datapoints are shown in Extended Data Figure 2-1 for which this legend also applies.