Effect of Sulpiride on Dopaminergic Synapse of Dorsal Hippocampus of Morphine-Treated Rats

Background: As previous studies show, several effects of morphine are induced by the dopaminergic system. Sulpiride is a dopamine D2 receptor (DAD2) antagonist widely used in clinics to treat DArelated disorders. DAD2 receptors are abundant at hippocampal cornu ammonis (CA1). Objectives: This study aimed to investigate the possible interaction of morphine and sulpiride on DA synapses in CA1. Materials & Methods: In this study, 48 Wistar rats weighing 220 to 250 g were used. These animals were classified into eight groups (6 rats per group): saline control group (1 ml/kg), morphine group (5 mg/kg), sulpiride groups alone (1, 2, and 4 mg/kg) and sulpiride groups (1, 2, and 4 mg/ kg)+morphine (5 mg/kg). Saline or substances were injected once intraperitoneally. After 48 h, the animals’ brains were removed under anesthesia and placed in 10% formalin for fixation. Then, 3- to 4-μm slices were cut from these tissues, and the DA synapse was examined by histochemistry and immunohistochemistry techniques. The data were statistically analyzed by the analysis of variance. Results: The control group had DA synapses and healthy neurons. A relative increase in DA synapses compared to the control group was observed in the morphine and single sulpiride groups. However, in sulpiride+morphine groups, DA synapses were reduced compared to morphine or sulpiride alone, but neurons were not destroyed. Conclusion: The interaction effect of sulpiride and morphine in the CA1 region may decrease DA synapses.