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 D۲ receptor (DAD۲) antagonist widely used in clinics to treat DArelated disorders. DAD۲ receptors are abundant at hippocampal cornu ammonis (CA۱). Objectives: This study aimed to investigate the possible interaction of morphine and sulpiride on DA synapses in CA۱. Materials & Methods: In this study, ۴۸ Wistar rats weighing ۲۲۰ to ۲۵۰ g were used. These animals were classified into eight groups (۶ rats per group): saline control group (۱ ml/kg), morphine group (۵ mg/kg), sulpiride groups alone (۱, ۲, and ۴ mg/kg) and sulpiride groups (۱, ۲, and ۴ mg/ kg)+morphine (۵ mg/kg). Saline or substances were injected once intraperitoneally. After ۴۸ h, the animals’ brains were removed under anesthesia and placed in ۱۰% formalin for fixation. Then, ۳- to ۴-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 CA۱ region may decrease DA synapses.

Keywords:

Morphine , CA۱ region , Hippocampus , Sulpiride , Dopamine , Synapses