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Golmohammadi H, Ghalandari-Shamami M, Haghparast A. Comparing the Effects of the Intra-DG Administration of Dopamine Receptor Antagonists’ Effects on Stress-induced Antinociception in Wistar Rats. BCN 2026; 17 (2) :323-336
URL: http://bcn.iums.ac.ir/article-1-3493-en.html

Introduction: The mesolimbic dopamine system is important in the modulation of pain and is activated under stress. Various types of stress can induce analgesia through the release of neurotransmitters and neuropeptides, such as dopamine. Accordingly, the present study investigated the role of dopamine receptors in the dentate gyrus (DG) of the hippocampus in two stress models of analgesia. 
Methods: One hundred and thirty-three adult male rats underwent stereotaxic surgery to place a unilateral cannula into the DG. After a one-week recovery period, separate groups of animals received different doses of the D1 receptor antagonist SCH-23390 (0.25, 1 and 4 μg/0.5 μL) or D2 receptor antagonist sulpiride (0.25, 1, and 4 μg/0.5 μL) or vehicle (0.5 μL DMSO or saline) into the DG, respectively. Animals were then exposed to forced swim stress (FSS) for 6 min or restraint stress (RS) for 3 hours, and then, pain thresholds were assessed in the tail-flick test over a 60-min period.
Results: Exposure to RS and FSS reduced pain responses in the tail-flick test, which was reduced by the inhibition of dopamine receptors. Intra-DG administration of SCH-23390 significantly reduced antinociceptive behaviors in the RS compared to the FSS. 
Conclusion: On the other hand, the effect of D2-like dopamine receptors in reducing FSS-induced analgesia was more prominent than RS.