Dried sheep placenta is sometimes used in traditional medicine to facilitate labour. The effects of an extract of
powdered dried sheep placenta with normal saline on guinea-pig uterus, ileum, spontaneously beating atrium and
Langendorff heart, rat uterus and hindquarters, and cat blood pressure were therefore examined. It was found that
1 g of dried sheep placenta had, on the guinea-pig uterus, an oxytocic activity equipotent with 0.075 0.32 i.u. of
oxytocin. The oxytocic activity was unaffected at pHs between 4 and 10 or by boiling for 30 min or autoclaving for
15 rain. Neither atropine nor promethazine inhibited the oxytocic action, but promethazine inhibited, to the same
degree, contractions induced in the ileum by equipotent doses of the infusion and histamine. Atropine, however, had
no effect on infusion-induced contractions in the ileum. The vasoconstriction induced in the rat hindquarters was
antagonized by promethazine and phentolamine. Cat blood pressure was reduced, but it had positive inotropic and
chronotropic effects on the spontaneously beating guinea-pig atrium and on the guinea-pig Langendorff heart. It was
concluded that the dried placenta contains a chorionic oxytocic substance the action of which is independent of
stimulation of H l receptors or of muscarinic receptors.
Keywords: Dried sheep placenta: Oxytocic effect: Mammalian smooth muscle: Langendorff heart