Effects of the Selective Serotonin Reuptake Inhibitor Fluoxetine on Social Behaviors in Male and Female Prairie Voles (Microtus ochrogaster)

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The selective serotonin reuptake inhibitor fluoxetine modifies social behavior in a number of species, including humans. Because the neural substrates for social behavior in prairie voles are sexually dimorphic, we tested whether the effects of fluoxetine on these behaviors differ by sex. Parental and pair-bonded voles were chronically treated with fluoxetine or saline and subsequently tested for parental responsiveness. Fluoxetine-treated animals displayed a longer latency to exhibit parental responsiveness than did saline-treated controls (p< 0.02), but they did not differ in other aspects of parental care. There were no sex differences in the effects of fluoxetine on parental behavior. After completion of the tests for parental behavior, the subjects were tested for aggressive behavior using the resident–intruder paradigm. Fluoxetine-treated males displayed less aggressive behavior than their saline-treated counterparts (p< 0.02). Although we did not find any effects of fluoxetine on aggressive behavior in females, no significant interaction was found between sex and treatment. Fluoxetine did not alter nonsocial behaviors. The findings suggest that serotonin influences social behavior in prairie voles.