Prenatal stress modifies behavior in offspring of bank voles (Clethrionomys glareolus).

The aim of the present study was to investigate the effect of prenatal stress on behavior of adult bank vole males and females. Pregnant females were submitted to stress by short encounters of two females at the same stage of pregnancy, to crowded condition by transfer to a cage with four to five nonpregnant females, or stressed by immobilization. The stressors were applied on Days 13, 14, and 15 of pregnancy. The results indicate that prenatal stress influenced adult offspring behavior tested in the presence of the same sex, as compared to controls. Females and males differ in their reactions to stress. Prenatal stress decreased the nonaggressive behavior of females but males did not change their amicable approaches toward males. In bank vole males, prenatal social or immobilization stress increased aggression, but females made more attacks only after prenatal stressing by immobilization. This indicates that in bank vole females classical stressor involved different mediators from those associated with prenatal social stresses. Our results indicate that prenatal stress in bank voles decreases the social activity of female offspring and increases aggression in male offspring. Social stress applied to females in late pregnancy may increase the number of aggressive males in a population.