Anxiolytic-like effect of paroxetine in a rat social interaction test.

The effects of short- and long-term administration of the selective serotonin reuptake inhibitor paroxetine were investigated in a rat social interaction test. A single administration of paroxetine at oral doses of 0.3, 1, 3 and 10 mg/kg had no effect on social interaction between pairs of male rats under bright light (high anxiety) conditions. After 21 days of daily administration, paroxetine given orally at 3 mg/kg significantly (p < 0.01) increased the time spent in social interaction by pairs of rats tested under the same conditions, with no effect on locomotor activity, indicating an anxiolytic-like effect. The magnitude of increase (+97%) was comparable to that seen after a single dose of chlordiazepoxide (4 mg/kg orally). Although there was also an increase in time spent in social interaction after 21 days of repeated oral administration of paroxetine at 0.3, 1, and 10 mg/kg (+44, +56, and +54% increases, respectively), statistical significance was not achieved. These results indicate that in the long term paroxetine has an anxiolytic action, and thus support the clinical evidence for its therapeutic use in the treatment of anxiety disorders in addition to its established role as an antidepressant.