Effect of curcumin on expression of μ opioid receptors in the spinal cord of morphine-dependent male rats

Introduction: Opioid drugs are the most potent analgesic drugs which are used as the first-line therapy for the management of acute severe pain. Long-term use of these drugs can lead to physical dependence and tolerance to their analgesic effect. Recent studies have shown that curcumin, the active ingredient of turmeric, reduces the symptoms of withdrawal syndrome in morphinedependent mice. Considering the important role of μ opioid receptors in the development of dependence, we hypothesized that the attenuating effect of curcumin on morphine dependence is mediated through the regulation of μ opioid receptors. Thus, the aim of this study was to evaluate the effect of curcumin on the expression of μ opioid receptors in the spinal cord of morphinedependent rats.Methods: Fifty male Wistar rats were treated with intraperitoneal (i.p.) injection of morphine for 9 days. Animals were randomly divided into 5 groups (n=10) as follows: control/saline group (morphine + normal saline), control/DMSO group (morphine + DMSO), and treatment groups (morphine + curcumin at doses of 2.5, 5 and 10 mg/kg, i.p.). On the 19th day, 5 animals from each group were randomly selected to assess withdrawal syndrome. The other animals were sacrificed and their spinal cord were removed and used to investigate the protein expression of μ receptors by using western blotting method.Results: Treatment with curcumin resulted in a significant and dose-dependent attenuation of withdrawal syndrome along with a decrease in the expression of spinal μ opioid receptors in morphine-dependent rats. The maximum effect was obtained from curcumin at the dosage of 10 mg/kg.Conclusion: The results of this study indicate that curcumin is capable of attenuating morphine dependence in rats through decreasing the expression of spinal opioid μ receptors.

Keywords:

Morphine , Curcumin , Opioid μ receptor , Withdrawal syndrome , Spinal cord , Western blot