Dose dependent effects of serotonergic agents on anxiety.

The role of serotonin in depression and anxiety is still highly controversial. In this experiment the effect of two substances upon anxiety was studied in rats. Forty adult (45-55 weeks old) male Wistar rats were used to study the following behavioral parameters on elevated plus maze test: open arm and closed arm entries; open arm, closed arm and central square activity duration, open arm preference and total distance traveled. A single injected dose of the antidepressant fluoxetine had no significant effect on animals' activity in the open-arm test, neither in a small dosage (5 mg/kgbw) nor in a higher one (10 mg/kgbw), whereas a single high dose of buspirone significantly impeded the open-arm activity of the rats. None of the substances influenced the general locomotor activity significantly, but the higher doses of buspirone mainly blocked the closed-arm entries and they even decreased the total distance traveled. Acute fluoxetine and buspirone administration influenced the rats' behavior in the elevated plus-maze test in a dose dependent manner. Anxiolytic effects occur after small doses but anxiogenic-like effects were noticed in rodents when higher doses were used.