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      Characterization of Estrogen Stimuli Sufficient to Initiate Cyclic Luteinizing Hormone Release in Acutely Ovariectomized Rats

      ,

      Neuroendocrinology

      S. Karger AG

      Hypothalamus, Pituitary, LH secretion, Estradiol, Progesterone, Receptors

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          Abstract

          Estradiol (E)-filled Silastic capsules were implanted subcutaneously to characterize the estrogen stimulus sufficient to initiate cyclic LH secretion in female rats ovariectomized on diestrus 1 of the estrous cycle. Such capsules elevate preoptic area, hypothalamic and hypophysial cell nuclear estrogen receptor levels to proestrous values within ½ h following insertion; upon removal of the capsules, nuclear receptor levels decline monotonically to ovariectomized control levels by 8 h in brain and 12 h in pituitary. Three parameters of the E stimulus were studied:latent period, duration, and continuity. E stimuli, short in duration (7–12 h) and discontinuous in nature (3 h pulses 12 or 15 h apart), effectively stimulated LH surges on ‘proestrus’. However, these stimuli had to begin 30 h prior to the onset of LH release. Such a latent period for estrogen action was not observed when we monitored the ability of the same E stimuli to enhance pituitary responsiveness to GnRH. These studies demonstrate that the ‘rate-limiting step’ for estrogen’s positive feedback action is located within the estrogen-sensitive brain circuits controlling GnRH release and defines the temporal characteristics of E stimuli activating these circuits.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1982
          1982
          26 March 2008
          : 34
          : 5
          : 315-322
          Affiliations
          The Rockefeller University, New York, N.Y. (USA)
          Article
          123320 Neuroendocrinology 1982;34:315–322
          10.1159/000123320
          7043298
          © 1982 S. Karger AG, Basel

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          Page count
          Pages: 8
          Categories
          Original Paper

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