Cannabinoids and the human uterus during pregnancy

Area of Science:

• Reproductive biology
• Pharmacology
• Molecular biology

Background:

• Cannabinoid receptors, CB(1) and CB(2), are present in various tissues, including the reproductive system.
• The role of cannabinoids in human uterine smooth muscle function during pregnancy is not fully understood.

Purpose of the Study:

• To investigate cannabinoid receptor expression in human pregnant myometrium.
• To evaluate the effects of endogenous and exogenous cannabinoids on myometrial contractility in vitro.

Main Methods:

• Human myometrial biopsy specimens were obtained during cesarean delivery.
• Isometric recordings were used to assess myometrial contractility.
• Cumulative doses of anandamide and Delta(9)-tetrahydrocannabinol were applied, with specific CB(1) and CB(2) receptor antagonists used to determine selectivity.
• Reverse transcription-polymerase chain reaction (RT-PCR) confirmed receptor expression.

Main Results:

• Both anandamide and Delta(9)-tetrahydrocannabinol demonstrated a direct, equipotent relaxant effect on human pregnant myometrium in vitro.
• The relaxant effect was specifically antagonized by the CB(1) receptor antagonist SR 141716, but not by the CB(2) receptor antagonist SR 144528.
• Expression of both CB(1) and CB(2) receptors was confirmed in human myometrium.

Conclusions:

• Endogenous and exogenous cannabinoids induce a potent, direct relaxation of human pregnant myometrium, mediated primarily through the CB(1) receptor.
• These findings suggest a potential role for endogenous cannabinoids in human parturition and pregnancy.
• The results do not support an independent link between exogenous cannabinoid use during pregnancy and preterm labor.