Assessing anxiolytic-like effects of selective serotonin reuptake inhibitors and serotonin-noradrenaline reuptake inhibitors using the elevated plus maze in mice.

The anxiolytic-like effects of selective serotonin reuptake inhibitors (SSRIs; paroxetine, fluvoxamine) and serotonin-noradrenaline reuptake inhibitors (SNRIs; milnacipran, venlafaxine) were compared with those of benzodiazepines (diazepam, chlordiazepoxide) and tricyclic antidepressants (imipramine, amitriptyline) using the elevated plus maze in mice. Paroxetine and fluvoxamine had no significant effects on the time spent in open arms and the number of open arm entries, even at a dose of 20 mg/kg p.o. On the other hand, milnacipran and venlafaxine showed a dose-dependent increase in the time spent in open arms and the number of open-arm entries. Significant effects were observed at doses of 10 and 20 mg/kg p.o. for both drugs. Diazepam and chlordiazepoxide showed potent anxiolytic-like effects, whereas imipramine and amitriptyline caused no anxiolytic-like effects. Like diazepam and chlordiazepoxide, milnacipran and venlafaxine increased the distance moved in open arms at the same dose levels showing anxiolytic-like effects. From these results, it may be concluded that SNRIs caused anxiolyic-like effects similar to benzodiazepines.