Induction of Pseudopregnancy in Rats by Vaginal Tampon

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Abstract
A plastic foam tampon was placed into the vagina of rats at various stages of the estrous cycle. After insertion of the tampon for 1-10 min., 69-80% of estrous and metestrous rats became pseudopregnant. Following removal of the tampon 4 hr. alter insertion, pseudopregnancy occurred in 100% of estrous or metestrous rats, in 19% of diestrous and in 46% of proestrous rats. When 4-day morulae were transferred at appropriate times into the uteri of recipient rats that had been treated with the tampon for 4 hr. at estrus, metestrus, diestrus and proestrus, 100, 92, 15 and 44% of the animals became pregnant, respectively. It appears that induction of pseudopregnancy by a vaginal tampon depends both on the duration of the stimulation and on the stage of the estrous cycle at the time of insertion.