The action of adrenaline and noradrenaline on the placental and foetal circulations in the rabbit and guinea‐pig

Abstract

The original object of the investigation was to find whether the placental barrier was permeable to adrenaline and to noradrenaline. It soon became apparent that whereas the placental vessels were very sensitive to these hormones, the foetus itself was relatively insensitive. These findings will now be described. METHODSThe observations were made on rabbits, 28-31 days pregnant, and guinea-pigs, 40-63 days pregnant. Light anaesthesia was maintained with urethane 1-5 g/kg body weight, injected intravenously. The guinea-pigs were lightly anaesthetized with ether while a vein was exposed for the injection. A maternal jugular vein was cannulated with fine polythene tubing for the infusion or injection of drugs. The maternal arterial blood pressure was recorded with a capacitance manometer from a carotid artery which was also cannulated with fine polythene tubing. The abdominal wall was opened by a mid-line incision under saline at 380 C. The uterus was cut longitudinally from rump to crown of a single foetus and that foetus was then delivered into the saline and supported throughout the experiment on a gauze sling. The foetal arterial blood pressure was recorded with a capacitance manometer from one carotid artery which was cannulated with a no. 19 record needle. Intrafoetal injections were made into the jugular vein or, in the guinea-pig, into the vitelline vein, towards the foetus. RESULTSL-Adrenaline, L-noradrenaline and oxytocin in the maternal circulation A continuous infusion of adrenaline, at the rate of 06 ,ug/kg/min, increased the maternal blood pressure by 10-25 mm Hg (with or without accelerating the heart rate) and caused vigorous contractions of the uterine muscle. The placenta became blue, the foetal heart rate fell from an average value of 300 per min to 150-170 per min, and the foetal blood pressure decreased from

The effect of hyperventilation on maternal placental blood flow in pregnant rabbits

“…Catecholamine injection in rabbits and guinea-pigs has been shown to cause foetal bradycardia, an effect which was ascribed to a severe PLACENTAL BLOOD FLOW reduction in maternal placental blood flow (Dornhorst & Young, 1952;Martin & Young, 1960). More recently, Bell (1968) has shown that noradrenaline caused constriction in isolated guinea-pig uterine arteries perfused at constant flow.…”

Influence of gestational age and hormones on experimental foetal bradycardia

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A single intravenous injection of adrenaline or noradrenaline into the maternal circulation causes a transient bradycardia of the exposed foetus in the near-term rabbit and guinea-pig (Dornhorst & Young, 1952); this was shown to be due to asphyxia consequent upon the reduction in maternal placental blood flow caused by constriction of the uterine arteries, and not due to any accompanying activity of the uterine muscle. The purpose of the present investigation was to study the influence of gestational age on this asphyxial bradycardia, in the guinea-pig foetus in utero.

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The Acute Autonomic Stress Response and Amniotic Fluid Glucocorticoids in Second-Trimester Pregnant Women

“…Moreover, although stress is capable of activating the adult ANS within seconds, the time it takes for the maternal ANS response to be measurable in the amniotic fluid is unclear. In pregnant rabbits and guinea pigs, continuous infusion of NE and EPI reduces placental blood flow causing fetal HR to decrease within 20 to 60 seconds after the infusion started (59). Likewise in humans, fetal HR decreases within 1 minute after a single injection of NE to the mother (60).…”