Abstract
Summary
The administration of norepinephrine (50 μg/kg) to the fetuses of nine sheep caused an increase in fetal arterial pressure (Control = 30 mm Hg; Test = 56 mm Hg; P > 0.001) and vasoconstriction in the fetal kidney (Control = 3.79 mm Hg × min/ml × kg; Test = 16.24 mm Hg × min/ ml × kg; P > 0.001), placental membranes (Control = 2.74 mm Hg × min/ml × kg; Test = 17.79 mm Hg × min/ml × kg; P > 0.004), and fetal cotyledons (Control = 0.178 mm Hg × min/ml × kg; Test = 0.706 mm Hg × min/ml × kg; P > 0.003). These results indicate the presence of alpha receptors in these organs. The uterine blood flow fell subsequent to the injection of norepinephrine to the fetus and this response was abolished by phenoxybenzamine blockade of the circulation of four fetuses even though we could demonstrate no phenoxybenzamine blockade in the uterine circulation of these animals.
Supported by Grant No. HD 06736.
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