Induction of pseudopregnancy in the Mongolian gerbil (Meriones unguiculatus) by vaginal stimulation

In rats, pseudopregnancy has been induced by mating with vasectomized males , by mechanical stimulation of the uterine cervix with a glass rod or vibra tor and by stimulation of the vagina with a tampon. On the other hand no pr actical data are available in reports on the induction of pseudopregnancy i n Mongolian gerbils. Pseudopregnancy of gerbils has been induced by mating with vasectomized males. But this method was uncertain because the incidenc e of pseudopregnancy was lower than that obtained in rats by other means. I n the present study, two experiments were undertaken as follows, I) Copulat ory behavior of gerbils was observed for one hour to determine the most eff ective stimulation interval. 2) From the results of Experiment 1, female ge rbils in estrus were mechanically stimulated to test the effectiveness of i nducing pseudopregnancy by vaginal stimulation at various time intervals. T he results of these experiments indicated that, although the frequency of c opulatory behavior varied among individuals, on average the most effective method for inducing pseudopregnancy was stimulation of 5 min duration and a t 20 or 30 min intervals. Because the incidence of pseudopregnancy induced by such mechanical stimulation (83.3%) was higher than that induced by mati ng with vasectomized males (30.0%), this method might be useful in inducing pseudopregnancy in Mongolian gerbils.