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      Anterior Pituitary Estradiol Receptors Associated with the Reinstatement of Ovulatory Cycles after Lactation Interruption in the Rat

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          The participation of adenohypophyseal estradiol receptors in the reinstatement of ovulatory cycles after lactation interruption was investigated. In rats whose pups were removed on day 13 postpartum (LRX), prolactin levels fell as from 1600 h on the same day, estradiol peaked on the morning of day 15 and gonadotropins and prolactin (PRL) surged on the afternoon of day 15. No significant changes in gonadotropins or estradiol levels were observed in rats which remained with their litters (LRP); in these rats daily afternoon surges of PRL were detected. No significant variations in anterior pituitary nuclear or cytosolic estradiol receptors were determined in LRP rats. In the nuclear fraction of LRX rats, an important increase (430.8 ± 124.9%) in receptor titers was observed on day 15. In these animals a significant increase (34.8 ± 1.3%) in cytosolic estradiol receptors was observed on day 14, followed by a fall on day 15 (–31.6 ± 6.6%) in comparison to day 13 levels. The receptor variations observed on day 15 closely resemble estrous cyclic changes determined in adult females. However, an observation which does not resemble those cycle variations is the increase in cytosolic receptors observed on day 14 in LRX rats. This increase may be the consequence of a decrease in dopamine levels induced by pup removal. To our knowledge this is the first time that the involvement of pituitary estradiol receptors in the reinstatement of ovulatory cycles after lactation interruption has been described.

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          Author and article information

          S. Karger AG
          08 April 2008
          : 59
          : 3
          : 265-270
          Instituto de Biología y Medicina Experimental, Buenos Aires, Argentina
          126667 Neuroendocrinology 1994;59:265–270
          © 1994 S. Karger AG, Basel

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          Page count
          Pages: 6
          Hypothalamic-Gonadal Axis


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