Failure of stressful stimuli to inhibit embryo implantation in the rat

The effects of stess by extreme temperature or immobilization on rat embryo implantation were investigated. One group of rats remained at 4 degrees C. at different days of progravidity. Other rats on L-3 of pregnancy remained at 39 degrees C. or immobilized. All the animals were put to death on L-6. The stressors produced no changes in either the per cent of rats implanting, the number of corpora lutea and implantation sites, or the weight of the ovaries and uteri. These results suggest that the process of nidation in the rat is resistant to several noxious environmental conditions.