The central goal of this project is to characterize the molecular events involved in the acquisition and extinction of emotional memory, using the behavioral paradigms of conditioned taste aversion (CTA) and condition fear (CF), respectively. A number of neuropsychiatric disorders, such as post traumatic stress disorder and schizophrenia display aberrations in the development of proper emotional associations. Numerous studies suggest that the amygdala and the medial prefrontal cortex (mPFC) are involved in the processing of emotion in the brain, and may display a role in the pathophysiology of schizophrenia and anxiety disorders. CTA and CF involve the development of long-term memory, which depends on gene transcription and protein synthesis in the amygdala. The studies described in this proposal will define the gene regulatory networks in the amygdala and the mPFC that are involved in emotional learning and memory.
Specific Aim 1 will define gene regulatory pathways that lead to long- term memory in CTA. These studies are divided in three stages. Initially, amygdala RNA is extracted at different times after one CTA trial and used to prepare 32P-labeled cDNA probes for cDNA microarray analysis. Thus, a time course of gene expression profiles for long-term memory of CTA is defined using cDNA microarrays. Next, from the genes that are expressed in the microarray analysis, a group of candidate genes is selected based on specific criteria and subjected to validation studies with Northern blots and in situ hybridizations. Finally, the expression data is used for gene cluster analysis, modeling, and the definition of gene regulatory networks. The gene networks and models are tested biologically with anti-sense knockdown approaches, protein kinase inhibitors, and protein kinase activity assays. Similarly, Specific Aim 2 will use cDNA microarrays to study NMDA receptor dependent changes in gene expression in mPFC and the amygdala as a result of extinction of fear conditioned behavior. Rather than erase the association between the conditioned and unconditioned stimuli, extinction of fear is thought to involve new learning. Previous work on the molecular basis of fear conditioning has focused solely on the acquisition phase, and has not examined extinction. Projections from the mPFC to the amygdala have been implicated in extinction. Projections from the mPFC to the amygdala have been implicated in extinction. Extinction-associated changes in the expression of selected candidate genes in mPFC and amygdala will be confirmed with Northern blots and in situ hybridization. Finally, the role of specific genes in extinction will be assessed using anti-sense knockdown approaches. These studies will provide important information as to the genetic basis of emotional learning and memory. Identifying information as to the genetic basis of emotional learning and memory. Identifying the genes activated during emotional learning is the first step in the development of future """"""""gene therapies"""""""" for emotional disorders.
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