Groups of old and young mice were ovariectomized and injected with hormones on a schedule to mimic the endocrine conditions of pregnancy. An artificial decidual stimulus, either trauma or the intraluminal injection of arachis oil, was applied to the left horn of the uterus and the decidual response assessed.
Following trauma, the uteri of the old mice produced significantly smaller deciduomata than those produced in the young mice. After the injection of oil there was no decidual response in the old mice, whereas in the young mice there was a good reaction in seven out of eleven animals.
It is concluded that the ability to form decidual tissue is considerably reduced in old mice, and it is suggested that this may be a significant factor in the senile reduction of litter size.