The dopamine D-3 antagonist U-99194A maleate increases social behaviors ofisolation induced aggressive male mice

Rationale: Blockade of D-1/D-2 dopamine receptors produce an antiaggressive action commonly associated with an impairment of other motor behaviors. Th e D-3 receptor seems to present opposite actions to the D-1 and D-2, since the blockade of this receptor produces stimulation of motor activity which has been associated with an increase in dopamine neurotransmission. Objecti ve: In this work, the action of the dopamine D-3 antagonist U-99194a maleat e on locomotor activity and in a social interaction test in male mice was e valuated. Methods: Animals isolated during 30 days were treated with U-9919 4a maleate (30-40 mg/kg) or saline and locomotor activity was measured 20 m in after drug administration. The behavioral interaction test was performed afterwards, between the experimental isolated animal and a standard oppone nt. Results: The higher dose used produces a significant decrease in sponta neous motor activity and presents an antiaggressive action without impairme nt of other behaviors, such as nonsocial exploration or immobility. At all doses tested, U-99194a maleate significantly increases social investigation . Conclusions: Our results give support to the hypothesis that the D-3 rece ptor could play a role in emotional behaviors.