The influence of buspirone, and its metabolite 1-PP, on the activity of paroxetine in the mouse light/dark paradigm and four plates test

Although numerous animal procedures have been employed in the study of antidepressants (ADs) in anxiety, the results following acute administration remain highly variable. The present study investigated the effect of the SSRI paroxetine (4, 8, and 16 mg/kg, IP) in two tests of anxiety in mice: the light/dark test paradigm, and the four plates test (FPT). In both tests, it was found that paroxetine resulted in an anxiolytic-like effect at doses that did not modify motor performance (at the doses of 4 and 8 mg/kg in the light/dark test and at the doses of 4, 8, and 16 mg/kg in the four plates test). In the light/dark paradigm, both doses of buspirone significantly potentiated paroxetine, while in the four plates only one dose of buspirone (a 5HT(1A) partial agonist) (0.06 mg/kg) increased the anxiolytic-like effect of paroxetine. Prior administration of 1-PP was without effect in the light/dark paradigm but antagonized the effect of paroxetine (at the dose of 0.06 and 0. 5 mg/kg) in the FPT. The results suggested that a balance between pre- and postsynaptic 5-HT(1A) receptor was implicated in the anxiolytic-like effect of paroxetine. Buspirone seemed to emphasize the role of paroxetine in 5-HT(1A) receptor modulation and exerted a biphasic influence in the two tests.