Distribution of AMPA receptor subunit glur1 in the bed nucleus of the stria terminalis and effect of stress.

The brain circuitry thought to be involved in stress responses includes several nuclei of the extended amygdala. The bed nucleus of the stria terminalis (BNST) is thought to be involved in the generation of sustained, nonspecific anxiety. Previous behavioral and electrophysiological experiments demonstrate that glutamate systems are involved in anxiety-like behaviors in the BNST. Antagonists for AMPA receptors injected into the BNST decrease anxiety-like behaviors. However, little is known about the role of AMPA receptors and the mechanism by which they act in the establishment of anxiety-like behavior in response to a stressor. We hypothesized that the distribution of AMPA receptors is changed following a paradigm of unpredictable footshock as has been seen in the basolateral amygdala (BLA). We examined the subcellular localization of the GluR1 subunits of the AMPA receptor. We found that the neuropil of the BNST had a lower density of dendritic spines compared to dendritic shafts in the BLA. The majority of elements immunolabeled for GluR1 were dendritic shafts and spines with axonal and glial elements rarely labeled. Compared with controls, no significant effect was observed on days 1, 6, or 14 poststress. However, there was a trend for an increase at 6 and 14 days poststress. These data demonstrate that GluR1 subunits are primarily located on postsynaptic elements in the BNST. Moreover, it was shown that the response of the AMPA GluR1 subunit does not undergo a significant migration into spines from dendrites in response to a stressor as has been demonstrated in the BLA.