Figure 5
β2-AR antagonist ICI 118,551 blocks OIH after chronic morphine or IBNtxA administration.
C57BL/6J mice received 4 days of morphine (20 mg/kg days 1–3, 40mg/kg day 4, s.c., twice a day, n = 15), or IBNtxA (2 mg/kg days1–3, 4 mg/kg day 4, s.c., twice a day, n = 15) treatment to induce OIH or vehicle (saline, s.c., n = 12). Chronic morphine or IBNtxA administration produces OIH assessed in thermal tests. (a,b) β2-AR antagonist ICI 118,551 (3.25mg/kg, s.c.) restores nociceptive responses to thermal stimuli back to baseline levels. Nociceptive latencies were not affected in vehicle treated animals (n = 8). (a) Thermal hyperalgesia was assessed by hot plate test and (b) cold allodynia by cold plate test. Error bars represent SEM. **p < 0.01, ***p < 0.001 vs. saline; ##p < 0.01, ###p < 0.001 vs. morphine or IBNtxA baseline respectively (two-way ANOVA combined with Tukey’s multiple comparison test).
