Endocannabinoid levels in the mouse uterus naturally fluctuate across the reproductive cycle, and activating cannabinoid receptors selectively reduced spontaneous uterine contractions during the dioestrus phase.
Readers curious about how cannabis might interact with reproductive physiology.
Endocannabinoid levels were significantly lower during the fertile phase of the cycle
What the researchers found
Anandamide and 2-AG levels in mouse uterine tissue were significantly lower during the oestrus (fertile) phase compared to the dioestrus phase. The uterus only showed spontaneous contractions during dioestrus, and these contractions were driven by prostaglandins.
Activating the CB1 receptor with the agonist ACEA reduced these spontaneous contractions, and CB2 activation with JWH133 had a smaller but similar effect. Neither agonist affected contractions triggered by external prostaglandins during the oestrus phase.
Blocking the enzymes that break down endocannabinoids (FAAH and MAGL) also reduced spontaneous contractions, suggesting that the body's own endocannabinoids naturally help modulate uterine muscle activity.
Why it matters
This research reveals that the endocannabinoid system is actively involved in regulating uterine muscle contractions across the reproductive cycle. For cannabis users, this suggests that THC and other cannabinoids could potentially interfere with normal uterine function by disrupting these finely tuned endocannabinoid fluctuations.
The numbers in context
Anandamide and 2-AG levels were significantly reduced during oestrus compared to dioestrus. CB1 agonist ACEA reduced spontaneous contractions. CB2 agonist JWH133 had a smaller but significant effect. FAAH inhibitor JNJ1661010 reduced contractions. MAGL inhibitor JZL184 had a lesser effect.
How the study worked
Researchers measured endocannabinoid levels in mouse uterine tissue at different cycle stages using liquid chromatography-mass spectrometry. Gene and protein expression of cannabinoid receptors and metabolic enzymes were quantified. Uterine contractility was tested in vitro using isolated tissue strips, with pharmacological tools including CB1 and CB2 agonists, their antagonists, and inhibitors of endocannabinoid-degrading enzymes.
What this study cannot tell us
This was a mouse study, and mouse reproductive cycles differ from human menstrual cycles. The in vitro contractility measurements used isolated tissue strips, which may not fully represent uterine behavior in a living organism. The study did not examine THC directly, instead using selective receptor agonists.
How to read the evidence
Preliminary evidence from a single animal study using selective pharmacological tools rather than cannabis itself.
When this study was published
Published in 2017. Foundational research on endocannabinoid involvement in uterine contractility.
The bigger picture
The endocannabinoid system appears in nearly every organ system, and this study adds reproductive smooth muscle to the list of tissues where it plays a regulatory role. Understanding how endocannabinoids naturally fluctuate in the uterus across the cycle is relevant to broader questions about how cannabis use might affect menstrual health, fertility, and pregnancy.
Questions still open
- Does cannabis use disrupt the natural endocannabinoid fluctuations in the human uterus? Could cannabinoid receptor modulation offer therapeutic benefits for conditions involving abnormal uterine contractions? How does chronic cannabis exposure affect reproductive endocannabinoid signaling?
Common questions
Does this mean cannabis affects periods or fertility?
Could cannabinoids be used to treat menstrual cramps?
Read the original research
Role of the endocannabinoid system in the control of mouse myometrium contractility during the menstrual cycle.
Biochemical pharmacology, 124, 83-93
Citation
Pagano, Ester; Orlando, Pierangelo; Finizio, Stefania; Rossi, Antonietta; Buono, Lorena; Iannotti, Fabio Arturo; Piscitelli, Fabiana; Izzo, Angelo A; Di Marzo, Vincenzo; Borrelli, Francesca. (2017). Role of the endocannabinoid system in the control of mouse myometrium contractility during the menstrual cycle.. Biochemical pharmacology, 124, 83-93. https://doi.org/10.1016/j.bcp.2016.11.023
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