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Updated: Aug 16, 2025
Live-cell Measurement of Odorant Receptor Activation Using a Real-time cAMP Assay
Published on: October 2, 2017
A novel Oprm1-Cre mouse maintains endogenous expression, function and enables detailed molecular characterization of
Juliet Mengaziol1, Amelia D Dunn1, Gregory Salimando2
1Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Abstract:
Key targets of both the therapeutic and abused properties of opioids are μ-opioid receptors (MORs). Despite years of research investigating the biochemistry and signal transduction pathways associated with MOR activation, we do not fully understand the cellular mechanisms underlying opioid addiction. Given that addictive opioids such as morphine, oxycodone, heroin, and fentanyl all activate MORs, and current therapies such as naloxone and buprenorphine block this activation, the availability of tools to mechanistically investigate opioid-mediated cellular and behavioral phenotypes are necessary. Therefore, we derived, validated, and applied a novel MOR-specific Cre mouse line, inserting a T2A cleavable peptide sequence and the Cre coding sequence into the MOR 3'UTR. Importantly, this line shows specificity and fidelity of MOR expression throughout the brain and with respect to function, there were no differences in behavioral responses to morphine when compared to wild type mice, nor are there any alterations in Oprm1 gene expression or receptor density. To assess Cre recombinase activity, MOR-Cre mice were crossed with the floxed GFP-reporters, RosaLSLSun1-sfGFP or RosaLSL-GFP-L10a. The latter allowed for cell type specific RNA sequencing via TRAP (Translating Ribosome Affinity Purification) of striatal MOR+ neurons following opioid withdrawal. The breadth of utility of this new tool will greatly facilitate the study of opioid biology under varying conditions.
Insights
Researchers developed a novel mouse model targeting μ-opioid receptors (MORs) to study opioid addiction mechanisms. This tool enables detailed investigation into cellular and behavioral effects of opioids, advancing addiction research.
Area of Science:
- Neuroscience
- Pharmacology
- Genetics
Background:
- Opioid addiction remains a significant challenge, with μ-opioid receptors (MORs) being central to both therapeutic effects and abuse potential.
- Current understanding of the cellular mechanisms driving opioid addiction is incomplete, despite extensive research on MOR signaling pathways.
- Existing opioid therapies and addictive substances interact with MORs, highlighting the need for precise tools to study these interactions.
Purpose of the Study:
- To develop and validate a novel MOR-specific Cre mouse line for mechanistic investigation of opioid-mediated phenotypes.
- To enable cell-type specific analysis of MOR-expressing neurons in the context of opioid use and withdrawal.
- To facilitate deeper understanding of the cellular and molecular underpinnings of opioid addiction.
Main Methods:
- Generation of a MOR-specific Cre mouse line by inserting Cre recombinase into the MOR 3'UTR.
- Validation of MOR expression specificity and fidelity across the brain.
- Crossing MOR-Cre mice with floxed GFP reporter lines (RosaLSLSun1-sfGFP or RosaLSL-GFP-L10a) for lineage tracing and cell-type specific RNA sequencing via TRAP (Translating Ribosome Affinity Purification).
Main Results:
- The MOR-Cre mouse line demonstrated specific and faithful MOR expression in the brain.
- No significant behavioral differences in response to morphine were observed compared to wild-type mice.
- TRAP RNA sequencing was successfully performed on striatal MOR+ neurons following opioid withdrawal, demonstrating the tool's utility.
Conclusions:
- The novel MOR-specific Cre mouse line is a validated and effective tool for studying opioid biology.
- This mouse line provides unprecedented opportunities to investigate MOR-related cellular and behavioral phenotypes.
- The tool will significantly advance research into the mechanisms of opioid addiction and potential therapeutic strategies.
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