Exogenous melatonin Action on hormonal levels, implantation sites and Mel1a receptor expression and PRL-II in ovaries of pinealectomized rats induced hyperprolactinemia

The study evaluated the effect of exogenous melatonin and the induction of hyperprolactinemia on estrogen, prolactin and progesterone levels, implantation sites and expression of Mel1a and PRL-II receptors in pinealectomized rats ovaries, during the third Initial pregnancy. We Used 35 rats divided into groups: I-rats Sham-pinealectomized (Sham); II – pinealectomized rats (P); III-pinealectomized rats treated with melatonin (P + Honey); IV-pinealectomized rats treated with domperidone (P + Domp); Pinealectomized V-rats treated with melatonin and domperidone (P + Honey/Domp); VI-rats treated with saline + ethanol (placebo honey) and VII-rats treated with saline solution (placebo domp). Melatonin (200μg/100g) and/or Domperidone (4mg/kg) was applied until the 7th day of gestation. The expression of the MEL1A receptor was low in the ovaries of rats P and P + Mel. The PRL-II receptor did not present differences between the groups as well as in the estrogen levels. Prolactin levels were elevated in rats treated with domperidone, while progesterone showed low levels in rats P and P + Domp. The weight and number of implantation sites were reduced in rats P and P + Mel, with no alteration in the weight of the ovaries. Thus, it is concluded that Hyperprolactinemia promotes an increase in the expression of the Mel1a receptor in the ovaries, at the beginning of pregnancy in pinealectomized rats, however without altering the expression of the PRLII receptor. In These animals, prolactin levels were kept elevated regardless of the presence or absence of melatonin, but there seems to be a synergistic effect when melatonin is associated with hyperprolactinemia and that melatonin is a preponderant factor for Maintenance of progesterone levels. Prolactin seems to play an important role during the implantation process.