Circulating concentrations of oxytocin during pregnancy in ewes

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Abstract
Oxytocin and progesterone were measured radioimmunologically during a control cycle, early pregnancy and during several time courses until term in 4 ewes of a local Moroccan breed of sheep. Oxytocin concentrations increased in a similar matter after day 3-4 of the control cycle or after mating and decreased on days 13-15 of early pregnancy .apprx. 2 days earlier than during the oestrous cycle. After days 18-19 of pregnancy oxytocin concentrations remained low until term at concentrations as observed during the non-luteal phase of the estrous cycle. Contrary progesterone concentrations remained high throughout gestation. Maternal recognition of pregnancy seems to have only a slight effect on the secretion pattern of oxytocin for a few days after day 12. A similar unknown mechanism during the cycle and early pregnancy is indicated for the vanishing oxytocin secretion and perhaps synthesis.