Effects of norBNI, (1,10 mg/kg), 5’-AMN (1 mg/kg), and 5’-MABN (1,10 mg/kg) on depression-related behaviour in mice. The time spent immobile (A), swimming (B) and climbing (C) during a 6 min FST is shown. In the TST, a decrease in average force corresponds to increased immobility (D). Depression-related behaviours were measured in the same groups of animals on successive days following a single injection of antagonist, and 30 min after U50,488 (5 mg/kg) or fluoxetine (10 mg/kg) administration. Data are expressed as mean ± SEM, n = 10 per group. Comparisons to saline: *P < 0.05, **P < 0.01, ***P < 0.001.