Introduction: Agonists of the Mu-opioid receptors (MOR), such as morphine are lengthily used for the treatment of moderate to pain, depression and anxiety. But the dose involved achieving adequate pain relief often elicits multiple unwanted side effects, including addiction and tolerance. Opioids produce their actions at a cellular level by activating MOR. These receptors are distributed throughout the central nervous system (CNS). The target of this study was the effect of Smyrnium cordifolium extract (SCE) on the hippocampus Cornu Ammonis 1 (CA1) aria MOR compared to clonidine.
Materials and methods: Extract of the aerial parts S.cordifolium was extracted by Soxhlet method. Addiction was created using the subcutaneous injections of morphine for 7 days. To evaluate the effects of SCE, the mice were divided up 5 groups. The first group (Control) received just morphine. The 2th group received morphine and Clonidine (0.2mg/kg). Groups 3, 4 and 5 were treated morphine and SCE (E1, E2 and E3). In all groups, on the seventh day 30 min after naloxone injection, their brains were perfusion with formaldehyde and removed for immunohistochemical investigation.
Results: The present immunohistochemical of the CA1 hippocampus study showed that group E1, there is a significant difference in MOR optical density compared to the control group at the level (P<0.05) and relative to the CLO group at the level (P<0.001). However, in groups E2, and E3 the MOR optical density increased compared to the control group and had a significant difference in level (P<0.001) and did not have a significant difference compared to the CLO group.
Conclusion: The study showed that with increasing S.cordifolium extract concentration, the optical density of MOR in the hippocampus increased, and this increase was dose-dependent. This increase in the CA1 hippocampus MOR optical density may be due to endocytosis or desensitization of MOR in neurons.