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

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).

This study aimed to investigate the possible interaction of morphine and sulpiride on DA synapses in CA1.

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.

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.

The interaction effect of sulpiride and morphine in the CA1 region may decrease DA synapses.