*M. M. MILLER, B. S. MCEWEN;
Lab. Neuroendocrinology, The Rockefeller Univ., New York, NY

Previous studies have found that rats that have been exposed to a single stressful event show enhanced anxiety many days to several weeks afterwards. These acute stress studies have often used a one-dimensional stressor, such as restraint, tailshock, or predator odor. It has also been shown that the inbred strain of Lewis rats have higher anxiety in general, and greater sensitivity to stress exposure, as demonstrated by their enhanced anxiety behavior. Recent research suggests that this is a product of their inability to produce a robust corticosterone response during the stress, and that the post-stress anxiety behavior expressed in the Lewis rat may be a model for post-traumatic stress disorder (PTSD). In order to further explore this idea, we attempted to enhance the acute stress experience and create a more complex episodic memory using a multisensory stressor. Male Lewis rats were first exposed to 10 minutes of a modified cat odor stress previously found to enhance anxiety seven days later (Cohen, et al. 2006). Immediately afterwards, rats were immobilized in flexible plastic cones for thirty minutes, and tailblood taken to determine corticosterone levels. A novel, neutral auditory stimulus (birdsong) was played throughout the stress episode. Seven days later, behavior was recorded in the elevated plus maze (EPM), either with or without the previously played birdsong. Rats were again tested two weeks later (three weeks post-stress) in the EPM, with or without birdsong. This stress paradigm elicited an enhanced anxiety response seven days later, as demonstrated by reduced time spent in the open arms of the EPM. Furthermore, anxiety behavior was negatively correlated with corticosterone levels: animals with higher corticosterone response during stress appeared to have less anxiety when examined seven days later. The effect of birdsong has yet to be determined, but we expect that this will work as a reminder cue for the stressful event, and further enhance anxiety. The work thus far reinforces the idea that activity in the hypothalamic-pituitary-adrenal axis and resulting corticosterone response play a large role in determining the extent of the adaptive/maladaptive behavioral changes seen after a single traumatic event, and demonstrate the functionality of using the Lewis rat as a model of PTSD.

Support Contributed By: NIMH Grant MH58911

Program No. 841.11/UU26
Poster presentation:Wednesday, Nov 07, 2007, 10:00 AM -11:00 AM
Location: San Diego Convention Center: Halls B-H