{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T20:33:20Z","timestamp":1777926800053,"version":"3.51.4"},"reference-count":0,"publisher":"S. Karger AG","license":[{"start":{"date-parts":[[2009,9,24]],"date-time":"2009-09-24T00:00:00Z","timestamp":1253750400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"},{"start":{"date-parts":[[2009,9,24]],"date-time":"2009-09-24T00:00:00Z","timestamp":1253750400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biol Neonate"],"abstract":"<jats:p>The cardiovascular and plasma catecholamine responses to hypoxemia following endogenous opioid blockade were evaluated in 18 late gestation fetal lambs (0.75\u20130.83 gestation) in utero. Hypoxemia was produced by progressive constriction of the umbilical cord with an inflatable silicone rubber cuff while fetal heart rate, blood pressure, and arterial blood gases were monitored. Fetal arterial blood samples were obtained for plasma catecholamine analysis using a radioenzymatic method. The animals were divided into 4 experimental groups. Control animals during normoxemia and following hypoxemia are represented by groups I and III, respectively. During umbilical constriction, arterial oxygen tension declined from 21.4 \u00b1 0.3 to 13.4 \u00b1 0.3 torr (p &lt; 0.001, mean \u00b1 SE) and was accompanied by an increase in blood pressure (44 \u00b1 1 to 53 \u00b1 1 torr), decrease in heart rate (176 \u00b1 4 to 114 \u00b1 4 beats\/min) and rise in plasma norepinephrine (437 \u00b1 90 to 3,410 \u00b1 617 pg\/ml) and epinephrine (53 \u00b1 10 to 1,074 \u00b1 325 pg\/ml). Naloxone infusion had no significant effect on the fetus during either normoxemic (group II) or hypoxemic conditions (group IV). Plasma catecholamines rose less in group IV than in hypoxemic control fetuses (norepinephrine: 2,407 \u00b1 406 vs. 3,410 \u00b1 617 pg\/ml; epinephrine: 966 \u00b1 641 vs. 1,074 \u00b1 305 pg\/ml), but the differences were not significant (p &gt; 0.2). It is concluded that endogenous opioids do not play a major role in the modulation of cardiovascular and sympathoadrenal adaptions to moderate hypoxemia in the fetus.<\/jats:p>","DOI":"10.1159\/000242596","type":"journal-article","created":{"date-parts":[[2009,9,28]],"date-time":"2009-09-28T10:11:01Z","timestamp":1254132661000},"page":"171-176","source":"Crossref","is-referenced-by-count":2,"title":["Effect of Endogenous Opioid Blockade on Fetal Cardiovascular and Sympathoadrenal Responses to Hypoxemia Induced by Umbilical Cord Constriction"],"prefix":"10.1159","author":[{"given":"Alan B.","family":"Lewis","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David A.","family":"Ferry","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"127","published-online":{"date-parts":[[2009,9,24]]},"container-title":["Biology of the Neonate"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.karger.com\/Article\/Pdf\/242596","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/karger.com\/article-pdf\/doi\/10.1159\/000242596","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T22:20:07Z","timestamp":1777674007000},"score":1,"resource":{"primary":{"URL":"https:\/\/karger.com\/article\/doi\/10.1159\/000242596"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2009,9,24]]},"references-count":0,"URL":"https:\/\/doi.org\/10.1159\/000242596","archive":["Portico"],"relation":{},"ISSN":["0006-3126","1421-9727"],"issn-type":[{"value":"0006-3126","type":"print"},{"value":"1421-9727","type":"electronic"}],"subject":[],"published":{"date-parts":[[2009,9,24]]}}}