title: Plasma catecholamine response to fetal hypoxemia is not potentiated by naloxone.
abstract: The interaction between the plasma catecholamine response to hypoxemia and endogenous opiate receptor blockade was investigated in 9 fetal lambs. The animals were randomly assigned to receive either normal saline (control group 1) or two doses of naloxone (group 2 = 0.5 mg/kg; group 3 = 1.0 mg/kg) by bolus injection followed by continuous infusion. Arterial PO2 decreased from 21 to 12 Torr and remained less than 14 Torr for 1 h. Arterial pH declined from 7.40 to a nadir of 7.32 at 1 h. Mean plasma catecholamine concentrations rose promptly from a baseline of 524-546 pg/ml for norepinephrine (NE) and 156-235 pg/ml for epinephrine (E) to reach a peak at 15 min (NE = 2,476-3,276, p less than 0.01; E = 1,856-4,065 pg/ml, p less than 0.01) and remained elevated thereafter. Neither dose of naloxone significantly altered plasma NE or E concentrations. Therefore, we conclude that endogenous opiates do not modulate the sympathoadrenal response to moderately long periods of hypoxemia unaccompanied by acidemia.
authors.affiliation: Division of Cardiology, Childrens Hospital of Los Angeles, Calif.
authors.forename: A B
authors.initials: AB
authors.lastname: Lewis
authors.forename: M
authors.initials: M
authors.lastname: Sadeghi
mesh_terms: D000818:Animals; D004357:Drug Synergism; D004837:Epinephrine / Q000097:blood* / Q000502:physiology; D005260:Female; D005311:Fetal Hypoxia / Q000097:blood*; D000860:Hypoxia / Q000097:blood*; D009270:Naloxone / Q000494:pharmacology*; D009638:Norepinephrine / Q000097:blood* / Q000502:physiology; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D012756:Sheep
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone; D009638:Norepinephrine; D004837:Epinephrine