Contextual negative cues appear to be important for induction of increased state of anxiety in prenatally stressed rats

Abstract

The startle reflex is highly sensitive to fear and anxiety in humans and animals. In humans, elevated startle magnitude is a marker for anxiety disorders. We have recently established an animal model for development of anxiety: Female rats are exposed to 2 stressful life events; prenatally (Dexamethasone injections) and postnatally in young adults (stressful blood sampling). Here, the blood sampling procedure three months prior to testing increased the basal startle, but only in prenatally stressed rats. In the present study, we wanted to investigate whether the increase in startle after a stress exposure was induced by a context or a general experience of stress, by exchanging the blood sampling with another stressful but dissimilar event, i.e. the Forced Swim Test.

We found that exposure of female rats to the Forced Swim Test was not associated with increased startle in the prenatally stressed rats. That the Forced Swim Test did not trigger the same startle response as the blood sampling, suggest importance of  contextual similarity in the test and stress situation, highlighting that lacking a contextual warning, prenatally stressed animals cope equally to controls with novel stressful exposures.