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. Author manuscript; available in PMC: 2016 Oct 22.
Published in final edited form as: J Psychopharmacol. 2015 Jun 4;29(7):812–821. doi: 10.1177/0269881115586937

Figure 1.

Figure 1

Antinociceptive effects of buprenorphine (Bup, 1mg/kg) and U50,488 (U50, 10 mg/kg) are blocked by naltrexone (NTX) in the mouse tail withdrawal assay. The time course of the experiments is shown (A,C, E). Bar charts highlight the antagonist effects of naltrexone (NTX) at 60 min post-administration of agonist (B, D). (A,B) Naltrexone (NTX) dose-dependently blocked buprenorphine-induced antinociception (**p< 0.01; ***p< 0.001 Bup compared to saline control; $$p< 0.01; $$$p< 0.001 Bup alone compared to combination Bup + NTX 1 and 3 mg/kg). (C,D) Naltrexone (NTX) dose-dependently blocked U50,488-induced antinociception (*p< 0.05; **p< 0.01; ***p< 0.001 U50 compared to saline control; $$p< 0.01; $$$p< 0.001 U50 alone compared to combination U50 + NTX 1 and 3 mg/kg). (E) Duration of κ-antagonist effects of naltrexone alone or naltrexone/buprenorphine combination. Significant blockade of U50,488 induced antinociception is evident at 1 h post-administration and reversed by 24 h. At 8h post-administration, the combination of buprenorphine/naltrexone, produced a significant potentiation of U50-488-induced antinociception (^^^p<0.001 compared to all other treatment groups; ### p<0.001 for all treatment groups compared to NTX/Bup/saline controls; && p<0.01 compared to NTX/Bup/saline controls and compared to NTX/Saline/U50 group. (F) The irreversible μ-antagonist CCAM (3 mg/kg) administered 24 h before testing blocked the NTX/Bup mediated potentiation of U50,488-induced antinociception at 8h post-administration (*p< 0.05 compared to U50 alone). All values are mean ± SEM, n= 5 per group.