The Effect of 2-Br-α-Ergocryptine on Mammary Blood Flow and Endocrine Changes at the Time of Parturition in the Ewe*

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Abstract
The influence was investigated of maternal prolactin concentrations on the changes in maternal mammary blood flow (MBF), and progesterone and estradiol concentrations which occur at the time of parturition in the ewe. In 6 sheep premature labor was induced by the administration of dexamethasone (1 mg/24 h) to the fetus. The drug 2-Br-.alpha.-ergocryptine was administered (1 mg/6 h) to 3 ewes to prevent the increase in maternal prolactin concentration which occurs at this time. When premature parturition was induced in 3 control animals, prolactin increased from 92.8 .+-. 8-330 .+-. 76 (SE) ng/ml. MBF, measured with electromagnetic flow probes chronically implanted around the mammary arteries, increased from 61 .+-. 12-215 .+-. 10 ml/min, uterine venous progesterone decreased from 35 .+-. 16-4 .+-. 1.5 ng/ml and estradiol increased from 42 .+-. 9-214 .+-. 33 pg/ml. Labor and delivery occurred 41 .+-. 3 and 52 .+-. 2 h, respectively, after the start of fetal dexamethasone infusion. In the group of animals receiving 2-Br-.alpha.-ergocryptine, prolactin decreased from 33 .+-. 7-1.9 .+-. 0.1 ng/ml. Although there was a significant difference between the concentrations of prolactin in the control and experimental groups (P < 0.001) during dexamethasone infusion, no differences could be detected between these groups in the changes in MBF, progesterone and estradiol concentrations, or the time of onset of labor or delivery. Maternal prolactin apparently does not have a causal role in these endocrinological and physiological events which occur during premature parturition in the ewe.

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