Morphine is an effective analgesic that acts by binding to the μ-opioid receptor (MOR) coded in the human by the OPRM1 gene. In the present study, we investigated the regulation of μ-opioid receptor (MOR-1) mRNA levels in all-trans-retinoic acid-differentiated SH-SY5Y human neuroblastoma cells under in vitro conditions with 10 μM morphine treatment for 24 h. In addition, we measured the MOR-1 levels in recombinant Chinese hamster ovary (CHO) cells, transfected with human μ-opioid receptor gene (hMOR) with 10 μM morphine treatment for 24 h. The isolated mRNA from these cells was subjected to real-time quantitative RT-PCR analysis to determine the regulation of μ-opioid receptor gene expression. It was observed that morphine treatment did not alter MOR-1 levels in undifferentiated SH-SY5Y cells compared to undifferentiated control cells. However, the MOR-1 levels in all-trans-retinoic acid-differentiated cells were significantly higher compared to the undifferentiated cells. Morphine treatment in differentiated SH-SY5Y cells caused significant downregulation of MOR-1 expression compared to the control cells. In the morphine-treated CHO cells, the hMOR-1 mRNA levels remained the same as the untreated control. Finally, pretreatment of SH-SY5Y cells with 10 μM naloxone, the antagonist of μ-opioid receptor, for 1 h significantly blocked the downregulation of MOR-1 mRNA levels with morphine treatment. These findings suggest that regulation of MOR-1 gene expression is cell-type specific after chronic morphine treatment and provide some evidence in the understanding of morphine tolerance.
Scientific advances have been made in various areas of medicine. However, morphine remains the leading opioid analgesic of choice for the treatment of moderate and severe pain. Although morphine has very potent analgesic actions, it also has adverse side effects which include the development of tolerance which is the reason for its limited use. The exact mechanisms underlying the development of opioid tolerance is unclear, but in recent years studies have shown that the phosphorylation of G‐coupled protein receptors by various kinases has been linked to receptor internalization. Preliminary studies in our lab yielded results indicative of a significant decrease in the gene expression of Src and EGFR after chronic 24 hrs morphine treatment in differentiated SH‐SY5Y human neuroblastoma cells. The present study was conducted to validate the expression of Src and EGFR by western blot analysis after chronic morphine exposure (10 μM) in the absence and presence of naloxone (10 μM) for 1 hr. Additional studies will determine the involvement of Src and EGFR in morphine‐induced MOR‐1 gene expression. The overall results from this study will provide an understanding on the molecular mechanisms of opioid tolerance and the role that the AKT pathway plays in the development of morphine tolerance. Research supported by NCRR/RCMI G12 RR03020 and G12 MD007582–28
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.