The dopamine D3 antagonist U-99194A maleate increases social behaviors of isolation-induced aggressive male mice

Rationale: Blockade of D1/D2 dopamine receptors produce an antiaggressive action commonly associated with an impairment of other motor behaviors. The D3 receptor seems to present opposite actions to the D1 and D2, since the blockade of this receptor produces stimulation of motor activity which has been associated with an increase in dopamine neurotransmission. Objective: In this work, the action of the dopamine D3 antagonist U-99194a maleate on locomotor activity and in a social interaction test in male mice was evaluated. Methods: Animals isolated during 30 days were treated with U-99194a maleate (20–40 mg/kg) or saline and locomotor activity was measured 20 min after drug administration. The behavioral interaction test was performed afterwards, between the experimental isolated animal and a standard opponent. Results: The higher dose used produces a significant decrease in spontaneous motor activity and presents an antiaggressive action without impairment of other behaviors, such as non-social exploration or immobility. At all doses tested, U-99194a maleate significantly increases social investigation. Conclusions: Our results give support to the hypothesis that the D3 receptor could play a role in emotional behaviors.