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.
