Gestational chronic mild stress: Effects on acoustic startle in male offspring of rats

An increasing number of scientific studies indicate that maternal stress during pregnancy influences fetal development of the nervous system and thereby the behavioural phenotype. We have previously reported attenuated prepulse inhibition (PPI) of the startle reaction in adult female rats derived from dams exposed to chronic mild stress (CMS) during gestation.

In humans, decreased PPI has been reported to be associated with anxiety. Because of its potential translational value across species, the modulation of startle reactivity may be a useful tool in examining altered emotional reactivity following prenatal insults. The present study aimed at investigating whether prenatally stressed male offspring would display altered startle phenotype.

Stress was induced by maternal gestational exposure to alternating procedures, i.e. CMS. At the age of 3 months, half of the offspring were blood sampled under restraint. At the age of 6 months, i.e. three months later, all animals were tested in the acoustic startle and the light enhanced startle (LES) paradigm.

Control and CMS male offspring showed similar basal startle and LES levels. Maternal gestational exposure to the relatively mild, variable paradigm of stressors affected the PPI response pattern in male rats. In prenatally manipulated males, the PPI response differed statistically significantly, depending on prior exposure to an episode of postnatal acute stress (blood sampling under restraint).

In contrast, the PPI response in control males was unaffected by this postnatal experience. The present work supports the hypothesis that the maternal environment is a long-term determinant of phenotypic differences in sensitivity to stressors.