INITIATION OF PARTURITION IN THE RABBIT BY MATERNAL AND FOETAL ADMINISTRATION OF CORTISOL: EFFECT OF RATE AND DURATION OF ADMINISTRATION: SUPPRESSION OF DELIVERY BY PROGESTERONE

Abstract

SUMMARY Continuous infusion of cortisol at rates from 0·31 to 1·24 mg/h into pregnant rabbits from day 21 of pregnancy onwards induced delivery in approximately 72 h. Similar rates of infusion into the foetal amniotic sac induced delivery with a shorter latency. Maternal infusion of 1·24 mg cortisol/h produced parturition providing it was continued for at least 24 h. If after this period the infusion was terminated, delivery still occurred after a further 48 h (i.e. 72 h in all). Progesterone administration to the mother blocked the effect of cortisol administered by the maternal or foetal route.