A Subset of β-Endorphin- or Dynorphin-Containing Neurons in the Medial Basal Hypothalamus Accumulates Estradiol

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Abstract
We used the combined steroid autoradiography-immunocytochemical method to determine whether estradiol- or dexamethasone-concentrating cells contain endogenous opioid peptides. Ovariectomized-adrenalectomized female rats were given highly radioactive doses of 3H-estradiol or 3H-dexamethasone, then sacrificed to demonstrate nuclear steroid binding. Autoradiograms were prepared, exposed for 2-12 months, photodeveloped, and fixed; immunocytochemistry was carried out on the same sections using antibodies to .beta.-endorphin or dynorphin A (1-17). In the medial basal hypothalamus, many estradiol- and some dexamethasone-concentrating neurons were found intermingled with .beta.-endorphin or dynorphin-immunoreactive neurons. Of the .beta.-endorphin-immunoreactive neurons in the medial basal hypothalamus, 4% concentrated estradiol in their nuclei. In addition, a subset of .beta.-endorphin-immunoreactive cells in the anterior pituitary concentrated estradiol in their nuclei. Although none of the .beta.-endorphin-immunoreactive neurons in the medial basal hypothalamus concentrated dexamethasone in their nuclei, many of the .beta.-endorphin-immunoreactive cells in the anterior pituitary did. Of the dynorphin-immunoreactive neurons in the medial basal hypothalamus, 10% concentrated estradiol in their nuclei. These data are consistent with the hypothesis of a genomic effect of estradiol on a particular subset of medial basal hypothalamic neurons that produce endogenous opioid peptides.