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Abstract:   (215 Views)
Background:­The periaqueductal gray­(PAG) region plays an essential role in the modulation of nociception. Also, PAG involved in reward circuitry by dopaminergic system in addiction. The present study assessed the blockades of D1-and D2-like receptors modify morphine self-administration via the periaqueductal gray region with and without exercise in rats.
Methods:­Exercise groups were trained to run on a treadmill for 4 weeks before surgery. The jugular vein was cannulated in animals, and they were allowed to access to the self-administration apparatus for daily receiving morphine. The experiment continued for 11 days. The effect of inhibition of D1- and D2 receptors­(via SCH23390 and Sulpiride; respectively) was investigated in morphine self-administration. The animals received the two antagonists earlier at dose of 4µg/0.5 µl by means of a pump injecting the compounds into the PAG region 5 min before receiving morphine. The numbers of lever pressing, infusion times, and withdrawal symptoms were measured.
Results:­The results showed the number of active lever pressing significantly increased in the morphine group compared with other groups in self-infusion during 11 days. Exercise significantly reversed the detrimental effects of morphine self -administration after five days. However, the synergistic effect of injected Sulpiride into the PAG region with exercise training was more pronounced on the amelioration of morphine than the combinatory effect of SCH23390 with exercise.
Conclusion:­The findings suggested that the D2 dopamine receptor in the PAG region involved in the morphine addiction via the dopaminergic system, and exercise training in combination with antagonists could reduce the rewarding properties of morphine.
Types of Manuscript: Original Research | Subject: Nervous system (others)