MAINTENANCE OF GESTATION IN ERGOTOXINE-TREATED PREGNANT RATS BY EXOGENOUS PROLACTIN

A single subcutaneous injection of ergotoxine ethanesulphonate into the rat terminates both pseudopregnancy and early pregnancy (Shelesnyak, 1955) and suppresses development of decidual tissue (Shelesnyak, 1954 a). The terminating action of ergotoxine on pregnancy and pseudopregnancy is associated with the appearance of vaginal and uterine signs of pro-oestrus and oestrus within 48 to 96 hours after the drug is injected (Shelesnyak, 1955). The action of ergotoxine can be blocked or reversed by administration of supplemental progesterone to the drug-treated animal (Shelesnyak, 1954 a, 1954 b, 1956 b). On the basis of the appearance of signs of oestrus and of the reversing action of concurrent additional progesterone, we postulated that the ergotoxine upsets the hormonal status which is necessary for normal pregnancy in its early stages (Shelesnyak, 1956 b, 1957 c). Investigations designed to elucidate the site and mechanism of ergotoxine action on nidation and deciduoma development have revealed that: (1)