The Endocannabinoid System Is Present in Embryos Before Brain Development Begins | Research

The takeaway

Researchers found that the endocannabinoid system, including CB1 receptors and the enzymes that make and break down endocannabinoids, is active in embryos before nerve cells even begin forming.

Read this if you are interested in how cannabis exposure during early pregnancy might affect embryonic development.

All major endocannabinoid system components were present before neurogenesis

What the researchers found

Using chick and mouse embryo models, researchers demonstrated that all major components of the endocannabinoid system are present during very early embryonic development, before neurogenesis (the formation of nerve cells) begins. This included CB1 receptors, the endocannabinoids anandamide and 2-AG, and the enzymes responsible for their production and breakdown.

The finding suggests the endocannabinoid system plays a role in fundamental embryonic development processes that precede brain formation, and that exposure to THC during this early window could disrupt these processes.

Why it matters

In utero THC exposure has been associated with increased risk of neurodevelopmental problems in offspring. This study provides a biological mechanism: if the endocannabinoid system is active even before brain development begins, cannabis exposure during the earliest stages of pregnancy could interfere with fundamental developmental processes.

The numbers in context

CB1 receptors, anandamide (AEA), 2-AG, and five metabolic enzymes (NAPE-PLD, DAGL-alpha, DAGL-beta, MAGL, FAAH) were all detected in pre-neurogenesis embryos in both chick and mouse models.

How the study worked

The study used biochemical techniques including analysis of receptor levels, endocannabinoid concentrations, and enzyme presence in chick and mouse embryo models at developmental stages before and during neurogenesis.

What this study cannot tell us

The study used animal models (chick and mouse), which may not perfectly mirror human embryonic development. Detecting the presence of endocannabinoid system components does not prove they are functionally critical at this stage. The study did not test the effects of THC exposure at these early timepoints.

How to read the evidence

Animal study in chick and mouse embryos; demonstrates presence of the system but does not test functional consequences of disruption.

When this study was published

Published in 2012. Research on endocannabinoid signaling in early development has continued to expand.

The bigger picture

This research extends the window of potential vulnerability to cannabis exposure further back in development than previously understood. If the endocannabinoid system is critical for pre-neurogenesis development, the earliest weeks of pregnancy, often before a woman knows she is pregnant, could represent a particularly sensitive period.

Questions still open

What specific developmental processes does the endocannabinoid system regulate before neurogenesis? Does THC exposure during this pre-neurogenesis window produce different outcomes than later exposure? Are these findings replicated in human embryonic tissue?

Common questions

Why does it matter that the endocannabinoid system exists before brain development?

If the endocannabinoid system is active before nerve cells even begin forming, it likely plays a role in fundamental embryonic processes. THC from cannabis use could interfere with these processes during the very earliest weeks of pregnancy, potentially before a woman is aware she is pregnant.

Does this prove cannabis causes birth defects?

No. This study showed the endocannabinoid system is present in early embryos, which is a necessary prerequisite for THC to have an effect, but it did not directly test whether THC exposure at this stage causes developmental problems. It identifies a potential vulnerability window that needs further investigation.

Read the original research

Cannabinoid receptor 1 signaling in embryo neurodevelopment.

Birth defects research. Part B, Developmental and reproductive toxicology, 95(2), 137-50

View on PubMed ↗Publisher’s paper ↗

Citation

Psychoyos, Delphine; Vinod, K Yaragudri; Cao, Jin; Xie, Shan; Hyson, Richard L; Wlodarczyk, Bogdan; He, Weimin; Cooper, Thomas B; Hungund, Basalingappa L; Finnell, Richard H. (2012). Cannabinoid receptor 1 signaling in embryo neurodevelopment.. Birth defects research. Part B, Developmental and reproductive toxicology, 95(2), 137-50. https://doi.org/10.1002/bdrb.20348