The effect of the uterine cervical stimulation at postpartum estrus upon the post-weaning fate of the lactational corpora lutea.

Effects of the uterine cervical stimulation applied at the postpartum estrus was examined in the lactating rats whose pups were removed on various days from 0 to 26 day after parturition. The changes of vaginal smear and the secretion pattern of progestins were followed. In the animals either with (experimental group) or without (control group) the stimulation, the continuation of lactation beyond 24 days after parturition caused the appearance of vaginal estrus. With the shorter lactation periods, however, vaginal estrus appeared only after weaning, and the average date of appearance was about day 3 of post-weaning in the control and day 13 in the experimental group. The length of the post-weaning diestrus in the experimental group coincided with that of