Cross-Species Comparison Found Surprisingly Little Overlap in Endocannabinoid Receptor Distribution Between Mice, Rats, and Monkeys | Research

The takeaway

Comparing endocannabinoid receptor gene expression across seven organs in mice, rats, and rhesus macaques, only 5 of 14 receptors had identical expression patterns across all three species, revealing a critical gap in translational cannabinoid research.

Cannabinoid researchers, pharmacologists, drug developers, translational scientists.

Only 5 of 14 endocannabinoid receptors matched across mice, rats, and monkeys

What the researchers found

Of 14 canonical and extended endocannabinoid receptors examined across 7 peripheral organs, only CB2, GPR18, GPR55, TRPV2, and FAAH had identical expression patterns in mice, rats, and rhesus macaques. Species- and organ-specific heterogeneity was substantial and previously unappreciated.

Why it matters

Most cannabinoid research uses rodent models, but if endocannabinoid receptors are distributed differently across species, findings in mice may not translate to primates or humans. This study reveals a fundamental challenge for the entire field.

The numbers in context

14 receptors tested across 7 organs in 3 species. Only 5 receptors (CB2, GPR18, GPR55, TRPV2, FAAH) matched across all species. Substantial species-specific and organ-specific variation in the remaining 9.

How the study worked

Comparative gene expression analysis of 14 endocannabinoid receptors in 7 peripheral organs of C57/BL6 mice, Sprague-Dawley rats, and rhesus macaques using quantitative methods.

What this study cannot tell us

Gene expression does not always correlate with protein levels or functional activity. Focused on peripheral organs, not brain regions. Limited to 3 species. Sample sizes per species not detailed. Preprint status (bioRxiv) means not yet peer-reviewed.

How to read the evidence

Comparative gene expression study across three species. Important finding but preprint (not yet peer-reviewed) and limited to gene expression levels.

When this study was published

Published as preprint in 2023.

The bigger picture

This finding has implications well beyond basic science. If a drug targets a cannabinoid receptor that is expressed differently in rodents than in primates, preclinical safety and efficacy data could be misleading. This may partly explain why some promising cannabinoid drugs fail in human trials.

Questions still open

How does human endocannabinoid receptor distribution compare to rhesus macaques?
Should cannabinoid drug development prioritize primate models over rodents?

Common questions

Do animal cannabinoid studies translate to humans?

This study found surprisingly little overlap in endocannabinoid receptor distribution between mice, rats, and monkeys, suggesting many rodent cannabinoid findings may not directly translate.

Which endocannabinoid receptors are consistent across species?

Only CB2, GPR18, GPR55, TRPV2, and FAAH had identical expression patterns across all three species tested.

Read the original research

Roadmap For The Expression Of Canonical and Extended Endocannabinoid System Receptors and Proteins in Peripheral Organs of Preclinical Animal Models.

bioRxiv : the preprint server for biology

View on PubMed ↗Publisher’s paper ↗

Citation

Rosado-Franco, J J; Ellison, A L; White, C J; Price, A S; Moore, C F; Williams, R E; Fridman, L B; Weerts, E M; Williams, D W. (2023). Roadmap For The Expression Of Canonical and Extended Endocannabinoid System Receptors and Proteins in Peripheral Organs of Preclinical Animal Models.. bioRxiv : the preprint server for biology. https://doi.org/10.1101/2023.06.10.544455