The Endocannabinoid System Helps Regulate Uterine Contractions, and Its Activity Shifts Across the Menstrual Cycle

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.

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 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.

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.