TY - JOUR
T1 - Norepinephrine regulation of fetal heart rate
T2 - Multiple mechanisms of action
AU - Cheung, Cecilia Y.
AU - Brace, Robert A.
N1 - Funding Information:
This study was funded in part by Grant HD20299 from the National Insitute of Child Health and Human Development and by an Es-tablished Investigatorship award from the American Heart Asso-ciation ot R. A. B.
PY - 1987/5
Y1 - 1987/5
N2 - Norepinephrine was infused intravenously for 30 minutes into chronically catheterized sheep fetuses averaging 133 days' gestation. At infusion rates of 3.9, 12, and 39 μg/min, heart rate initially decreased as much as 40 bpm and then gradually increased to 50 bpm above the control value by the end of the infusion. Thereafer, heart rate increased further, and by the end of a 30-minute recovery period, heart rate was still 66 bpm above the control value. In fetuses pretreated with either a ganglionic blocker or a parasympathetic blocker, norepinephrine caused a large and sustained rise in heart rate by 124 bpm, which declined rapidly when the infusion was terminated. These results suggest that circulating norepinephrine affects fetal heart by several mechanisms: (1) a baroreceptor-mediated suppression, (2) a direct stimulation by norepinephrine, (3) a gradual weakening of the vagal suppression, and (4) an increase in cardiac sensitivity to sympathetic stimulation. In addition, there appears to be a long-term positive correlation between fetal heart rate and circulating norepinephrine levels.
AB - Norepinephrine was infused intravenously for 30 minutes into chronically catheterized sheep fetuses averaging 133 days' gestation. At infusion rates of 3.9, 12, and 39 μg/min, heart rate initially decreased as much as 40 bpm and then gradually increased to 50 bpm above the control value by the end of the infusion. Thereafer, heart rate increased further, and by the end of a 30-minute recovery period, heart rate was still 66 bpm above the control value. In fetuses pretreated with either a ganglionic blocker or a parasympathetic blocker, norepinephrine caused a large and sustained rise in heart rate by 124 bpm, which declined rapidly when the infusion was terminated. These results suggest that circulating norepinephrine affects fetal heart by several mechanisms: (1) a baroreceptor-mediated suppression, (2) a direct stimulation by norepinephrine, (3) a gradual weakening of the vagal suppression, and (4) an increase in cardiac sensitivity to sympathetic stimulation. In addition, there appears to be a long-term positive correlation between fetal heart rate and circulating norepinephrine levels.
KW - Fetus
KW - autonomic nervous system
KW - heart rate
KW - norepinephrine
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U2 - 10.1016/0002-9378(87)90157-8
DO - 10.1016/0002-9378(87)90157-8
M3 - Article
C2 - 3578444
AN - SCOPUS:0023196523
SN - 0002-9378
VL - 156
SP - 1254
EP - 1259
JO - American journal of obstetrics and gynecology
JF - American journal of obstetrics and gynecology
IS - 5
ER -