Figure 2. Attenuation of the antidepressant-like effects of dextromethorphan, but not imipramine, by σ₁ receptor antagonism.

Pretreatment with the σ₁ receptor antagonist BD1063 (10 mg/kg, i.p.) prevented the dextromethorphan (30 mg/kg, i.p.)-induced decrease in immobility time (A). BD1047 (10 mg/kg, i.p.) pretreatment also produced a noticeable, albeit not statistically significant, trend toward the prevention of the decreased immobility time induced by dextromethorphan (B). In contrast, the antidepressant-like effect of imipramine (20 mg/kg, i.p.) in the forced swim test was not significantly prevented by BD1063 pretreatment (C). Data shown are expressed as mean ± S.E.M. *P<0.05, ***P<0.001, compared with the saline-treated group; #P<0.05, compared with the dextromethorphan-treated group; one-way ANOVA followed by post-hoc Tukey's tests. IM, imipramine. DM, dextromethorphan.