[Tokolysis and dose-dependent effects of beta-blocking with atenolol in the rabbit]

In 11 pregnant rabbits we induced labor by parenteral infusion of Dinoprost (F2) (0.05 mg/min). By application of Fenoterol (0.01 mg/min) we had complete labor inhibition (P). Increasing dosages of Atenolol (T1 = 0.05 mg/min, T2 = 0.10 mg/min, T3 = 0.25 mg/min) followed. We registered systolic, diastolic and mean blood pressure directly after punction of a femoralis, cardiac frequency, and labor by integration of action potentials of uterus. Cardiac frequency decreased with increasing amounts of Atenolol. Mean blood pressure fell significantly under Fenoterol medication. There is no further decrement by additional application of high dosages of Atenolol. A certain dosage of Atenolol could be defined, that does not increase labor activity under Fenoterol medication but does decrease cardiac frequency without influence on mean blood pressure.