Plant-derived and synthetic cannabinoids worked through different receptor combinations in mice
THC required both CB1 and CB2 receptors for its full effects in mice, while the synthetic cannabinoid XLR11 worked through CB1 alone, and GPR55 receptors appeared to oppose cannabinoid effects.
Quick Facts
What This Study Found
CB1 deletion abolished tetrad effects for all three cannabinoids. CB2 deletion abolished THC and WIN55,212-2 analgesia and catalepsy but not XLR11's. GPR55 deletion enhanced responses to THC and WIN55,212-2. These findings held for both systemic and central (intraventricular) administration.
Key Numbers
Three cannabinoids tested across four mouse genotypes. CB2 knockout abolished THC analgesia and catalepsy but not XLR11's. GPR55 knockout enhanced responses to phytocannabinoids. Pharmacological results matched genetic findings.
How They Did This
Compared tetrad effects (analgesia, hypothermia, catalepsy, locomotor suppression) of THC, WIN55,212-2, and XLR11 in wildtype, CB1-knockout, CB2-knockout, and GPR55-knockout mice. Pharmacological antagonists confirmed genetic findings.
Why This Research Matters
The assumption that all cannabinoid effects are mediated solely through CB1 is incomplete. Plant cannabinoids and synthetic cannabinoids may engage different receptor combinations, which has implications for both therapeutic development and understanding synthetic cannabinoid toxicity.
The Bigger Picture
Understanding that plant and synthetic cannabinoids work through different receptor mechanisms could explain why synthetic cannabinoids produce more severe and unpredictable effects than plant cannabis, and could guide safer therapeutic development.
What This Study Doesn't Tell Us
Animal study using knockout mice, which may develop compensatory mechanisms. Only three cannabinoids tested from a large and diverse class. Tetrad effects are a simplified measure of cannabinoid pharmacology.
Questions This Raises
- ?Could GPR55 antagonists enhance the therapeutic effects of medical cannabis?
- ?Do the different receptor requirements explain the different toxicity profiles of plant vs. synthetic cannabinoids?
- ?Would these receptor distinctions hold in human pharmacology?
Trust & Context
- Key Stat:
- CB2 needed for THC's effects but not for synthetic cannabinoid XLR11
- Evidence Grade:
- Well-designed preclinical study using both genetic and pharmacological approaches, but limited to mouse models and three compounds.
- Study Age:
- 2020 animal study. Challenges the CB1-centric model of cannabinoid pharmacology.
- Original Title:
- Different receptor mechanisms underlying phytocannabinoid- versus synthetic cannabinoid-induced tetrad effects: Opposite roles of CB1 /CB2 versus GPR55 receptors.
- Published In:
- British journal of pharmacology, 177(8), 1865-1880 (2020)
- Authors:
- Wang, Xiao-Fei(2), Galaj, Ewa(6), Bi, Guo-Hua(8), Zhang, Cindy, He, Yi, Zhan, Jia, Bauman, Michael H, Gardner, Eliot L, Xi, Zheng-Xiong
- Database ID:
- RTHC-02905
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
What is the tetrad test?
The cannabinoid tetrad is a standard set of four behavioral tests in rodents: analgesia (pain relief), hypothermia (temperature drop), catalepsy (immobility), and locomotor suppression. All four are characteristic effects of cannabinoid receptor activation.
What is GPR55?
GPR55 is a receptor sometimes called the "third cannabinoid receptor." This study found it appears to oppose the effects of CB1 and CB2, as removing it enhanced responses to THC and WIN55,212-2.
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Cite This Study
https://rethinkthc.com/research/RTHC-02905APA
Wang, Xiao-Fei; Galaj, Ewa; Bi, Guo-Hua; Zhang, Cindy; He, Yi; Zhan, Jia; Bauman, Michael H; Gardner, Eliot L; Xi, Zheng-Xiong. (2020). Different receptor mechanisms underlying phytocannabinoid- versus synthetic cannabinoid-induced tetrad effects: Opposite roles of CB1 /CB2 versus GPR55 receptors.. British journal of pharmacology, 177(8), 1865-1880. https://doi.org/10.1111/bph.14958
MLA
Wang, Xiao-Fei, et al. "Different receptor mechanisms underlying phytocannabinoid- versus synthetic cannabinoid-induced tetrad effects: Opposite roles of CB1 /CB2 versus GPR55 receptors.." British journal of pharmacology, 2020. https://doi.org/10.1111/bph.14958
RethinkTHC
RethinkTHC Research Database. "Different receptor mechanisms underlying phytocannabinoid- v..." RTHC-02905. Retrieved from https://rethinkthc.com/research/wang-2020-different-receptor-mechanisms-underlying
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.