Disruption of early pregnancy by direct and indirect exposure to novel males in mice: comparison of influences of preputialectomized and intact males.

Inseminated female CF-1 mice (Mus musculus) were exposed on days 1 to 5 of pregnancy to unfamiliar outbred males. In the first experiment, inseminated females were each housed directly with the sire, a preputialectomized male, or an intact male. Both types of novel male attempted to mate with the female during this period, unlike the sire. Reinsemination occurred in a significant proportion of the females that were exposed to novel males; this effect was equivalent for preputialectomized and intact males. In two subsequent experiments, we refined a paradigm of indirect exposure to novel males through a wire-mesh grid, which prevents mating and reinsemination. Two or three males housed directly above each female through a grid disrupt pregnancy in most cases, but housing the males below the females is much less likely to do so. In a final experiment, each inseminated female was housed below two males that were either preputialectomized or sham-preputialectomized. Whereas 29 of 33 undisturbed controls were parturient, only eight of 32 females exposed to sham-preputialectomized males and six of 32 exposed to preputialectomized males were parturient. These results suggest that nonvolatile pheromones are involved in novel-male-induced pregnancy disruptions, but that preputial gland emissions are not necessary for such disruptions.