Myometrial oxytocin receptor expression and intracellular pathways.

Oxytocin (OT) signalling plays a fundamental role in the mechanisms of parturition. OT is one of the most frequently used drugs in obstetrics, promoting uterine contractions for labor induction and augmentation and to prevent postpartum hemorrhage (PPH). Expression of the oxytocin receptor (OTR) in the human myometrium is tightly regulated during pregnancy and its levels have been shown to peak upon labour onset and to fall sharply in advanced labour and the postpartum period, when the uterus become refractive to OT. However, uterine sensitivity to OT varies between pregnant women, probably reflecting differences in their myometrial OTR expression. Control of OTR expression is mediated by a combination of steroid hormone stimulation, stretch, and inflammation. This review summarises current knowledge regarding the complex regulation of myometrial OTR expression and its associated intracellular signaling pathways.