Effects of SCH 23390, Raclopride, and Haloperidol on Morphine Withdrawal-Induced Aggression in Male Mice

Abstract

RODRÍGUEZ-ARIAS, M., J. PINAZO, J. MIÑARRO AND L. STINUS. Effects of SCH 23390, raclopride, and haloperidol on morphine withdrawal-induced aggression in male mice. PHARMACOL BIOCHEM BEHAV 64(1) 123–130, 1999.—Dopamine seems to play a very important role in aggressive behavior observed in morphine withdrawal. The effect of SCH 23390 (0.5 mg/kg), raclopride (0.3 mg/kg), and haloperidol (0.1 mg/kg) on morphine withdrawal-induced aggression has been studied in this work. Mice were rendered dependent by a daily injection of morphine (2.5 mg/kg) for 14 days. Three different experiments were carried out with the objective to evaluate the antiaggressive effect of the dopamine antagonists on: first, spontaneous morphine withdrawal; second, naloxone-induced withdrawal; and third, naloxone-induced withdrawal after previous administration of the neuroleptics. Thirty minutes after injection of the dopamine antagonists, experimental animals were confronted in a neutral area with anosmic, group-housed conspecifics (standard opponents), and aggression was evaluated by estimation of times allocated to 11 different behavioral categories. Morphine withdrawal produced an increase in aggressive behavior and a decrease in social and nonsocial behaviors. The three neuroleptics counteracted this aggression, but when SCH 23390 (selective D 1 antagonist) and haloperidol (mixed D 1/D 2 antagonist) were administered in naloxone-induced withdrawal, the effect was greater in comparison to the spontaneous withdrawal. However, no changes were observed after raclopride administration (selective D 2 antagonist). In conclusion, the alterations in the dopaminergic system produced by opiate withdrawal depend on the type of withdrawal produced, and this produces a change in the antiaggressive potency of the dopamine antagonists.