[Abstract Title]. - Society for Neuroscience

Poster
294. Gene Expression and Fear Learning
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 294.8/SS48
Topic: F.02.f. Fear and aversive learning and memory
Support: NSF Grant IBN-0129809
Title: State anxiety in the rat: gene expression in the amygdala, hippocampus and prefrontal
cortex
Authors: *M. DONLEY, J. B. ROSEN;
Dept Psychology, Univ. Delaware, Newark, DE
Abstract: Several areas of the brain are known to be important in the learning and memory of
fear, including the amygdala, the hippocampus, and the prefrontal cortex. Although the amygdala
is critical for fear conditioning, it has been suggested that the amygdala is not only active during
times of overt fear, but also during times of uncertainty and ambiguity, when state anxiety levels
are higher than normal. Using a behavioral test and the immediate-early gene, egr-1, we find that
during high or low levels of state anxiety, activity in the lateral nucleus of the amygdala (LA)
responds differently when experiencing a novel (uncertain) environment. High and low levels of
state anxiety were induced by handling rats in either a quiet or noisy room for 7 days.
Behaviorally, when tested in an open field test on the eighth day, rats handled in a quiet
environment show higher levels of anxiety (high state anxiety), whereas rats handled in an
intermittently noisy environment show lower levels of anxiety (low state anxiety). Another set of
quiet and noisy handled rats were divided into 3 groups: handled control, exposure to a novel
chamber without footshock (context-no-shock), or contextually fear conditioned. Behaviorally,
high and low state anxiety rats were indistinguishable, those fear conditioned froze after shock,
while context-no-shock rats explored, but did not freeze. Thirty minutes after context exposure
or fear conditioning, rats were sacrificed and in situ hybridization for egr-1 was performed. Both
fear-conditioned high and low state anxiety rats had significantly increased egr-1 in the LA.
Interestingly, in the context-no-shock condition, low state anxiety rats had egr-1 levels in the LA
similar to handled rats, whereas high state anxiety rats had increased egr-1 levels similar to fear
conditioned rats. The data suggest that high state anxiety rats experience more uncertainty in a
novel environment, and therefore have higher amygdala activation than low state anxiety rats.
Egr-1 expression in the amygdala is contrasted with that in the hippocampus. Levels of egr-1 in
CA1 of the hippocampus were similarly increased in high and low state anxiety rats compared to
handled controls, whether they were fear conditioned or in the context-no-shock condition. The
findings indicate that the amygdala is involved in emotional information processing, even if it