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Updated: May 18, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
07:23

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities

Published on: July 29, 2014

Regulation of mammalian MOR-1 gene expression after chronic treatment with morphine

Rose V Prenus1, Ebens Luscar, Zhi-Ping Zhu

  • 1College of Pharmacy and Pharmaceutical Sciences, Florida A__AMB__M University, Tallahassee, FL 32307, USA.

International Journal of Molecular Medicine
|September 21, 2012
PubMed

Insights

Morphine

Area of Science:

  • Neuroscience
  • Pharmacology
  • Molecular Biology

Background:

  • Morphine is a potent analgesic acting on the µ-opioid receptor (MOR), encoded by the OPRM1 gene.
  • Understanding MOR regulation is crucial for pain management and opioid tolerance.
  • SH-SY5Y neuroblastoma and CHO cells are used as in vitro models.

Purpose of the Study:

  • To investigate the effect of morphine on µ-opioid receptor (MOR-1) mRNA levels in differentiated and undifferentiated SH-SY5Y cells.
  • To examine MOR-1 mRNA regulation in morphine-treated Chinese hamster ovary (CHO) cells.
  • To determine if naloxone can block morphine-induced downregulation of MOR-1.

Main Methods:

  • Real-time quantitative RT-PCR was used to measure MOR-1 mRNA levels.
  • SH-SY5Y cells were differentiated with all-trans-retinoic acid.
  • Cells were treated with 10 µM morphine for 24 hours, with or without naloxone pretreatment.

Main Results:

  • Morphine did not affect MOR-1 levels in undifferentiated SH-SY5Y cells.
  • Differentiated SH-SY5Y cells showed higher MOR-1 levels than undifferentiated cells.
  • Morphine significantly downregulated MOR-1 in differentiated SH-SY5Y cells but not in CHO cells.
  • Naloxone pretreatment blocked morphine-induced MOR-1 downregulation in differentiated SH-SY5Y cells.

Conclusions:

  • µ-opioid receptor (MOR-1) gene expression regulation is cell-type specific in response to morphine.
  • Findings suggest a mechanism contributing to morphine tolerance.
  • This study provides insights into the complex regulation of opioid receptors.

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