THE INFLUENCE OF PROGESTERONE, RELAXIN AND ESTROGEN ON SOME STRUCTURAL AND FUNCTIONAL CHANGES IN THE PRE-PARTURIENT MOUSE

Abstract

Some normal physiological and anatomical adaptations preceding and following parturition in the mouse were described. The work of Hall and Newton (22) was confirmed by direct measurement technique. Unilateral ovariectomy on day 16 of pregnancy did not influence cervical softening or symphyseal separation. It did bring about a highly significant increase in responsiveness to oxytocin of the delivery mechanism on the 19th day-of-pregnancy. Progesterone treatment decreased responsiveness to oxytocin injection of the 19th day-of-pregnancy in intact, unilaterally or bilaterally ovariectomized pregnant mice. Pretreatment with relaxin markedly increased responsiveness to oxytocin and induced interpubic ligament formation in bilaterally ovariectomized progesterone-maintained mice. Estradiol 17-[beta] over a wide dosage range did not duplicate these effects. Cervical softening progessed in the absence of ovarian tissue in progesterone-maintained pregnant mice.