Involvement of Basolateral Amygdala Dopamine D1 Receptors in the Acquisition and Expression of Morphine-Induced Place Preference in Rats

BACKGROUND: In the present study, the effects of intra-basolateral amygdala (BLA) blockade of dopamine D1 receptor on morphine-induced conditioned place preference (CPP) were investigated in male Wistar rats. MATERIALS AND METHODS: A 5-day CPP paradigm was used. Morphine was injected subsequently at effective (5 mg/kg) and ineffective (0.5 mg/kg) doses. SCH 23390 (0.5– μg/rat), as a selective D1 receptor antagonist, was microinjected bilaterally into the BLA. RESULTS: Effective dose of morphine induced a significant CPP, and increased the locomotor activity during the testing phase. The results showed that morphine-induced CPP was significantly suppressed by D1 receptors antagonist in BLA in the acquisition phase and caused an aversion even at high doses. The antagonist also significantly prevented CPP expression. Morphine increased the motor activity, but the D1 receptors blockade, significantly reduced it. CONCLUSIONS: The findings of this study suggest a possible role for BLA dopamine D1 receptors in reward responses in morphine dependency.