The amygdala is a brain structure that plays a crucial role in fear and anxiety, and the actions of anxiety-reducing compounds. The opioid peptide has also been shown to modulate anxiety-related responses within the amygdala. Using herpes virus-mediated gene transfer, we have demonstrated that overexpression of enkephalin in the amygdala enhances the anxiety-reducing influences of the benzodiazepine diazepam (Valium) in rats. These initial results demonstrate that herpes virus-mediated gene transfer can transiently alter expression of neuropeptides in confined brain sites of adult rats, and that these changes can modify behavioral responses. The present studies continue to utilize this powerful technique to examine the role of amygdalar enkephalin in regulating anxiety-related behaviors and the actions of anxiolytic drugs. Both decreases and cell-targeted increases in peptide expression will be examined in several animal models of anxiety.
Aim 1 will verify the ability of virus-mediated gene transfer to decrease and cell-specifically increase expression of enkephalin in select areas of amygdala. Anatomical and quantitative methods will assess changes in mRNA expression, while peptide changes will be assessed with immunohistochemistry and radioimmunoassay.
AIM 2 examines if altered enkephalin expression in central amygdala modifies anxiety-related behaviors in additional animal tests of anxiety behaviors and/or the effectiveness of other anxiolytics in these tests. These studies 1) compare decreases with cell-specific increases in enkephalin expression, 2) test the activity of other anxiolytics (alcohol, the serotonergic compound buspirone), and 3) tests effects in several models of anxiety.
AIM 3 assesses the effects of pharmacological modulation of enkephalin activity in amygdala. Using more traditional techniques selective opioid receptor (mu, delta) agonists and antagonists will be locally applied in amygdala, and the effect of these compounds on responses to anxiolytic drugs will be tested. These studies will lead to a better understanding of the role of amygdala and enkephalin in anxiety and anxiolytic responses, as well as elucidate the differences between animal models of anxiety. This understanding may also suggest novel, avenues for development of treatments for anxiety or affective disorders.
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