| PROLONGED EFFECTS OF ACUTE STRESS ON ANXIETY BEHAVIOR
AND MORPHOLOGY IN REGIONS OF THE AMYGDALA AND FRONTAL CORTEX |
| M.M.Miller*; C.Liston; B.S.McEwen |
| Lab. of Neuroendocrinology, Rockefeller Univ, New York,
NY, USA |
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Recent studies suggest that acute stress can induce long-term
cellular and molecular modifications to the brain. Reconstructions
of iontophoretically dye-loaded neurons in the amygdala and frontal
cortex were used to analyze structural changes that occur after acute
stress. Rats were subjected to two hours of acute immobilization stress
followed by ten days of rest before behavior was examined. Both stress
and control groups were handled daily prior to and after the stress
day. Behavior was recorded during a five-minute exposure to an open
field grid, and perfused brains were collected two hours afterward.
Behavioral results suggest that acute stress increased anxiety-like
responses to an open field ten days later. Stressed rats crossed fewer
lines in the center of the open field and spent significantly less
time in the center than controls. Individual neurons from sections
containing the lateral and basolateral (LA/BLA) amygdala of both groups
were iontophoretically injected with Lucifer Yellow, and these cells
were identified and traced. Pyramidal neurons from the orbitofrontal
(OFC) and infralimbic (IL) cortices were also injected and traced.
No differences in dendritic length were detected in the LA/BLA cells;
however, cells in the OFC and IL showed opposing trends in dendritic
arborization following stress. Using confocal laser scanning microscopy,
regions of apical and basal dendrites were randomly sampled at intervals
of 50 m from the cell body.
Spine counts using deconvolved optical image stacks revealed a difference
in dendritic spine density between the stress and control groups for
certain cell types in LA/BLA. These results are consistent with previous
Golgi-staining evidence finding delayed changes in dendritic spine
density in the amygdala after acute stress (Mitra et al., 2005), and
demonstrate that iontophoretic cell-loading can be used as a tool
to examine neuronal morphology in the amygdala and frontal cortex.
Support Contributed By: MH58911, MH41256
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