Effect of melatonin on estrogen and progesterone receptors in relation to uterine contraction in rats

Pharmacol Res. 2003 Apr;47(4):349-54. doi: 10.1016/s1043-6618(03)00014-8.


The present study was designed to investigate the possible modulator effect of melatonin on uterine estrogen and progesterone receptors in rats as well as the uterine response to oxytocin. Non-pregnant rats were pretreated with melatonin in a dose of 0.8 mg kg(-1) per day for 15 consecutive days. Control animals received the vehicle. The uterus was dissected out and uterine contraction in one horne was recorded in vitro for each animal as a response to oxytocin (0.5 x 10(-11) to 2 x 10(-11)M). The other uterine horne was subjected to estrogen and progesterone receptors detection by immunohistochemical and image analysis techniques. The results reveal a significant reduction (59%) in the number of uterine estrogen receptors with concomitant increase in the progesterone receptors (53%) in melatonin-pretreated rats as compared to the control ones. In addition, our data show an inhibitory effect of melatonin on the uterine contraction as a response to oxytocin (0.5 x 10(-11), 1 x 10(-11), and 2 x 10(-11)M) amounting to 48, 77, and 59.5% reduction, respectively, in the amplitude of contraction as well as 62, 19.9, and 47% reduction in the area under the curve (AUC) of uterine contractions, respectively. The data, so far obtained, may indicate a possible relationship of melatonin-induced modulation of the number of estrogen and progesterone receptors and its inhibitory effect on uterine contraction. These findings merit further investigations on the possible beneficial role of melatonin in a plethora of hormone-dependent uterine disorders.

MeSH terms

  • Animals
  • Antioxidants / pharmacology*
  • Female
  • Melatonin / pharmacology*
  • Oxytocin / pharmacology*
  • Rats
  • Rats, Wistar
  • Receptors, Estrogen / drug effects*
  • Receptors, Progesterone / drug effects*
  • Uterine Contraction / drug effects*
  • Uterine Contraction / physiology


  • Antioxidants
  • Receptors, Estrogen
  • Receptors, Progesterone
  • Oxytocin
  • Melatonin