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Intra-accumbal administration of the mGlu8 receptagonist,(S)-3,4-DCPG, inhibit the acquisition but has no effect on the expression of morphine-induced CPP
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Nazanin Kahvandi   , Zahra Ebrahimi , Seyed Asaad Karimi , Siamak Shahidi , Iraj Salehi , Abdolrahman Sarihi |
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Abstract: (213 Views) |
Introduction: The nucleus accumbens (NAc) plays a critical role in drug reward. It has been reported that metabotropic glutamate receptors (mGlu receptors) play a key role in the rewarding pathway(s). Previous studies have shown the vast allocation of the different types of mGlu receptors, including mGlu8 receptors, in regions that are associated with opioid rewards, such as the NAc. The present study aimed to evaluate the role of mGlu8 receptors within the NAc in the acquisition and expression phases of morphine-induced conditioned place preference (CPP).
Methods and Materials: Adult male Wistar rats were bilaterally implanted by two cannulas in the NAc and were evaluated in a CPP paradigm. To investigate the effects of mGlu8 agonist on the acquisition of morphine-induced CPP, bilaterally intra-accumbal injection of S-3,4-DCPG (0.03, 0.3, and 3 μg/0.5 μL) was done 5 min before each morphine injection (5 mg/kg) during the 3 days of conditioning phase. To examine the effects of the S-3,4-DCPG on the expression of morphine-induced CPP, the highest dose (3 μg/ 0.5 μL) of S-3,4-DCPG was bilaterally administered into the NAc 5 min before the CPP test.
Results: The results revealed that intra-accumbal administration of S-3,4-DCPG (0.3 and 3 μg) markedly decreased the acquisition in a dose-dependent manner but had no effect on the expression of morphine-induced CPP.
Conclusion: Repeated exposure to opioids enhances the function of mGlu receptors and presynaptic. Stimulation of these receptors results in reduced glutamate release. The findings suggest that activation of mGlu8 receptors in the NAc dose-dependently blocks the establishment of morphine-induced CPP and reduces the rewarding properties of morphine which may be related to the glutamate activity into the NAc and in reward pathway(s).
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| Keywords: Metabotropic glutamate receptor type 8, Nucleus accumbens, Conditioned place preference, Morphine, Rat |
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Full-Text [PDF 321 kb]
(25 Downloads)
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Type of Study: Research |
Subject:
General
Received: 2024/02/11 | Accepted: 2023/08/23 | Published: 2023/08/23
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