*M. M. MILLER1, C. LISTON1, P. HOF2, J. H. MORRISON2, B. S. MCEWEN1;
1Laboratory of Neuroendocrinology, Rockefeller Univ, New York, NY, 2Fishberg Department of Neuroscience, Mount Sinai School of Medicine, New York, NY.

Recent studies suggest that regions of the brain involved in learning and memory, such as the hippocampus, amygdala, and prefrontal cortex, are highly plastic at the cellular level and responsive to stress. Chronic stress has been shown to enhance anxiety behavior and fear memory and decrease performance on non-fear related tasks. Chronic restraint experiments have found significant dendritic retraction and decreased spine density in the rat medial prefrontal cortex (mPFC) following 21 days of restraint stress (Radley, et al. 2004, Radley, et al. 2006), and even one week of brief restraint stress appears to induce mPFC dendritic atrophy (Brown, et al. 2005).
In order to examine whether a single, traumatic stress can produce dendritic remodeling in the mPFC or alter anxiety behavior, rats were subjected to two hours of acute immobilization stress followed by ten days of rest. Behavior in the elevated plus maze (EPM) was recorded on the tenth day, and perfused brains were collected two hours later and sectioned. Layer II/III pyramidal neurons from the anterior cingulate were iontophoretically injected with Lucifer Yellow dye, and these cells were identified and reconstructed in 3D using the program Neurolucida (Microbrightfield, Inc).
No overall effect was found between the acute stress and control groups for EPM anxiety behavior, as measured by the percent of time spent in the open arms. Likewise, there was no overall difference in mean total apical or basal dendritic length or number of branch points between groups. However, further analysis revealed that total apical dendritic arbor and the time spent in the open arms of the EPM were positively correlated, particularly in the acute stress group. Rats that showed enhanced anxiety, spending less time in the open arms of the EPM, also had reduced total apical dendritic material in the anterior cingulate, and the magnitude of the stress effect on dendritic arborization predicted the behavioral measures of anxiety. Examining these individual differences may be relevant to understanding why some people exposed to a given trauma develop post-traumatic stress disorder while others do not.
Support Contributed By:NIMH Grant MH58911

Program No. 58.13/U4
Poster presentation:Saturday, Oct 14, 2006, 1:00 PM - 2:00 PM
Location: Georgia World Congress Center: Halls B3-B5