Sex Differences in Immediate Early Genes in Retrosplenial Cortex Following Context Fear Learning

Aleia Olson, “Sex Differences in Immediate Early Genes in Retrosplenial Cortex Following Context Fear Learning”
Mentors: James Moyer, Hanna Yousuf & Chad Smies, Psychology

Many people experience traumatic events that lead to long-lasting fear memories that are key components of anxiety disorders. Pavlovian conditioning can be used to model fear learning. Females express more susceptibility to fear learning compared to males. For example, female mice show stronger context fear learning compared to male mice. While some studies have shown sex differences in context fear learning, other work did not observe sex differences in short-term acquisition. They observed sex differences in molecular mechanisms that may underlie differences in later retrieval of fear learning. Fear-related research has been mostly focused on male subjects, and little is known about the molecular mechanisms that underlie sex differences in fear learning. We examined a brain region that is involved in context fear learning called the retrosplenial cortex (RSC). Contextual fear conditioning involves exposing a rat to an aversive stimulus (e.g., footshock) so that the rat learns to associate the environment (context) with the footshock. The rat expresses fear in a form immobility (freezing). The following day, a memory test is given by placing the rat back in the same testing chamber without presenting the footshock. One hour following the memory retrieval test, brains are extracted and processed. We are currently measuring immediate early gene (IEG) expression by using western blot analysis to quantify sex- and learning-related changes in expression. IEGs are activity markers that are induced by environmental stimuli. It will be interesting to see if there are any sex differences in IEG expression, as this would suggest that the molecular mechanisms may differ between males and females. These data may aid in understanding why women tend to be more susceptible to developing fear memories.


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