Anxiolytic-like effects of olanzapine, risperidone and fluoxetine in the elevated plus-maze test in rats

In the present study was examined the effect of treatment with olanzapine or risperidone, given separately or in combination with fluoxetine, in the elevated plus-maze test (an animal model of anxiety) in male Wistar rats. The obtained results showed that treatment with olanzapine (1 mg/kg), risperidone (0.1 and 0.3 mg/kg) or fluoxetine (5 and 10 mg/kg) induced an anxiolytic-like effect in the elevated plus-maze test. Olanzapine, risperidone and fluoxetine, tested in doses effective in the model of anxiolytic-like actions, did not affect motor coordination, while olanzapine (3 mg/kg) and risperidone (0.3 mg/kg) produced a significant reduction of exploratory activity in the open field test. In a combination study, the anxiolytic-like effect of olanzapine or risperidone was significantly antagonized by co-treatment with fluoxetine. Additionally, co-treatment with olanzapine or risperidone and fluoxetine disturbed the motor coordination of rats in a rota-rod test. These findings indicate that olanzapine, risperidone and fluoxetine per se may be clinically effective in treating anxiety disorders, but their effects may be attenuated when they are used in combination with other medications.