Prenatal influence on behavior of offspring of crowded mice.

Pregnant albino mice were subjected to stress by crowding. When the litters encountered unfamiliar stimuli, they were less active, they were slower to respond, and they defecated less than control mice. These differences persisted at 30 and 100 days of age, whether the mice were raised by a crowded or by an uncrowded mother, and in spite of starvation. One explanation may be that aberrant endocrine activity in the crowded, pregnant female impairs the development of fetal response systems.