THE EFFECT OF LONG TERM TREATMENT WITH A β‐ADRENOCEPTOR BLOCKER, l‐PROPRANOLOL, ON THE DISTRIBUTION OF CARDIAC OUTPUT OF THE LATE GESTATIONAL GUINEA‐PIG

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Abstract
1. The effects of daily administration of propranolol on the distribution of cardiac output were studied in the late pregnant guinea-pig. 2. The animals were given either saline, 5 or 50 mg/kg per day of l-propranolol for 15 days during the last trimester of gestation. 3. Blood flow responses were assessed by injecting 15 microns microspheres into the conscious animal one to two days prior to parturition. 4. The fraction of cardiac output reaching the placentas was significantly reduced in both groups (P less than 0.5 and P less than 0.001, respectively), while flow to all other organs studied remained unaltered. 5. It is suggested that propranolol exerts a selective effect on the placental vascular bed in the guinea-pig.