QUANTITATIVE STUDIES ON DECIDUOMA FORMATION AND IMPLANTATION IN THE LACTATING RAT.

Abstract

Deciduoma formation and the capacity for ovum implantation were used as an index of uterine sensitivity during the luteal phase following postpartum ovulation. This luteal phase, which was rigidly controlled, was initiated by suckling stimuli (2 or 8 young/litter) and/or cervical stimuli (mechanical or mating). In all groups, the magnitude of the deciduoma response was greatest following knife-scratch trauma of the endometrium on Day 4. The endometrium by Day 6 showed either a reduction or an absence of sensitivity. The increase in the size of the suckling litter to 8 young not only reduced the magnitude of the deciduoma response to the Day 4 trauma, but prolonged the state of uterine sensitivity as well, thereby resulting in a bimodal sensitivity curve. It was the second portion of this curve, however, that best correlated with the ability of blastocysts to induce decidua formation. Even with a controlled environment, delays in implantation from 2 to 13 days were noted with this degree of suckling stimul...