Suppression of estrus in female mice by the presence of conspecifics or by foot shock.

The reaction of reproductive system of outbred female mice to crowded conditions or electric foot shock was investigated. Both experimental factors inhibited estrous cycle, and decidual cell reaction (DCR) was observed after traumatization of uterine horns in tested animals. Further investigations showed that corpora lutea in females subjected to social stress were significantly larger than those in mice stressed by classical stressor. Also, plasma progesterone level increased only in females exposed to grouped females. These results indicate that social interaction among female mice lead to the development of typical pseudopregnancy, whereas inhibition of ovulation and DCR in females subjected to electric foot shock are not related to the increase of activity of corpora lutea.