{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,4]],"date-time":"2026-06-04T00:08:13Z","timestamp":1780531693297,"version":"3.54.1"},"reference-count":0,"publisher":"S. Karger AG","license":[{"start":{"date-parts":[[2008,4,7]],"date-time":"2008-04-07T00:00:00Z","timestamp":1207526400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"},{"start":{"date-parts":[[2008,4,7]],"date-time":"2008-04-07T00:00:00Z","timestamp":1207526400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Neuroendocrinology"],"abstract":"<jats:p>The density of \u00b5-opiate receptors located in the medial preoptic area (MPOA) of the rat hypothalamus is cyclical and sexually dimorphic. The hormonal regulation of MPOA \u00b5-receptors was examined in ovariectomized rats treated with a variety of hormone regimens. In experiment 1, animals received acute estradiol (E&lt;sub&gt;2&lt;\/sub&gt;), progesterone (P), or prolactin (PRL), or E&lt;sub&gt;2&lt;\/sub&gt; followed in 48 h by either P or vehicle by subcutaneous injection. Brains were removed 3 h after the final injection. In experiment 2, animals were implanted with empty or E&lt;sub&gt;2&lt;\/sub&gt;-filled Silastic capsules, and received either P or vehicle by injection 48 h later, at which time E&lt;sub&gt;2&lt;\/sub&gt; capsules were removed. One group received E&lt;sub&gt;2&lt;\/sub&gt; implants which remained in place following sham removal surgery. Brains and trunk blood for radioimmunoassay of E&lt;sub&gt;2&lt;\/sub&gt; and P were collected 3, 27 or 51 h after the final injection. Frozen brain sections were prepared, incubated in [3H]D-Ala2, MePhe4, Gly-ol5-enkephalin, which selectively labels \u00b5-receptors, and analyzed using quantitative receptor autoradiography. P treatment significantly increased MPOA \u00b5-receptors, but only 27 h after E&lt;sub&gt;2&lt;\/sub&gt; priming. Neither shorter P exposure, nor E&lt;sub&gt;2&lt;\/sub&gt;, P or PRL alone affected MPOA \u00b5-recepter density. Following this delayed E&lt;sub&gt;2&lt;\/sub&gt;, P-induced increase, \u00b5-receptor density subsequently decreased in the presence or absence of E&lt;sub&gt;2&lt;\/sub&gt;. The results suggest that E&lt;sub&gt;2&lt;\/sub&gt;, P treatment produces a gradual and transient increase of MPOA \u00b5-receptor density. The subsequent decrease of receptor density is independent of the presence of E&lt;sub&gt;2&lt;\/sub&gt; and may be related to receptor turnover. The time course of this effect is consistent with that of the estrus cycle. Such hormone-induced regulation of MPOA \u00b5-receptor density could influence the physiologic effects of opiates on gonadotropin secretion and reproductive behavior in cycling females.<\/jats:p>","DOI":"10.1159\/000126096","type":"journal-article","created":{"date-parts":[[2008,4,7]],"date-time":"2008-04-07T07:33:24Z","timestamp":1207553604000},"page":"51-58","source":"Crossref","is-referenced-by-count":35,"title":["Dynamic Patterns of Medial Preoptic \u03bc-Opiate Receptor Regulation by Gonadal Steroid Hormones"],"prefix":"10.1159","author":[{"given":"Annabelle R.","family":"Mateo","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mai","family":"Hijazi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ronald P.","family":"Hammer, Jr.","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"127","published-online":{"date-parts":[[2008,4,7]]},"container-title":["Neuroendocrinology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.karger.com\/Article\/Pdf\/126096","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/karger.com\/article-pdf\/doi\/10.1159\/000126096","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T19:30:42Z","timestamp":1777663842000},"score":1,"resource":{"primary":{"URL":"https:\/\/karger.com\/article\/doi\/10.1159\/000126096"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2008,4,7]]},"references-count":0,"URL":"https:\/\/doi.org\/10.1159\/000126096","archive":["Portico"],"relation":{},"ISSN":["0028-3835","1423-0194"],"issn-type":[{"value":"0028-3835","type":"print"},{"value":"1423-0194","type":"electronic"}],"subject":[],"published":{"date-parts":[[2008,4,7]]}}}