Clinical significance of melatonin receptors in the human myometrium.

OBJECTIVE

To review and update the research on melatonin receptor expression in the human myometrium, in particular as it pertains to uterine contractility at labor.

DESIGN

Summary of previous studies with the addition of new data on the transcriptional regulation of melatonin receptor expression in human myometrial cells.

SETTING

Not applicable.

PATIENT(S): Late-term pregnant volunteers.

INTERVENTION(S): Biopsy collection for in vitro analyses provided the original data. More recently, uterine contractions in late-term pregnant volunteers were assessed before, during, and after acute white-light exposure.

MAIN OUTCOME MEASURE(S): Melatonin receptor signaling in myometrial cells and uterine contractions in late-term pregnant volunteers.

RESULT(S): Melatonin acts through the MTNR1B melatonin receptor that is expressed in the myometrium at late term to synergistically enhance oxytocin-dependent signaling and contractions. Acute inhibition of endogenous melatonin levels with light reversibly suppresses uterine contractions.

CONCLUSION(S): These results point to a significant role for circulating melatonin in the timing and degree of uterine contractions in late-term pregnancy. Understanding the regulation of melatonin receptors remains a future objective.