2005 — 2008 |
Day, Heidi E |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
The Role of the Central Amygdala and Bst in Stress @ University of Colorado At Boulder
DESCRIPTION (provided by applicant): A wealth of evidence has suggested that psychological stress can precipitate or exacerbate many medical conditions, including psychiatric illnesses. One brain system that is thought to be very important for responses to stress, fear and anxiety is the central extended amygdala. This proposal is based on the assumption that knowledge of how a major output nucleus of the amygdala (the central nucleus, CEA) and a related brain region, the bed nucleus of the stria terminalis (BST) normally responds to psychological stress will ultimately help us to understand the etiology of some disorders influenced by stress. Because of the demonstrated role in fear and anxiety behaviors, a significant effort has previously been directed at demonstrating activation of the CEA. However, it has recently been shown that exposure to the psychological stress of novelty, loud noise or restraint results in a decrease (~50 percent) in amphetamine-induced c-fos mRNA expression in enkaphalin-containing neurons of the oval nucleus of the BST (BSTov) and lateral division of the CEA (CEAI), suggesting that psychological stress in fact inhibits these brain regions. Potentially, inhibition of these neurons, that are also GABAergic, would result in disinhibition of their efferent targets. These targets include the fusiform nucleus of the BST, the lateral parabrachial nucleus, and the medial CEA that collectively regulate several autonomic, endocrine, and behavioral responses that are altered by stress and anxiety. The experiments described in this application are designed to further characterize the effects of psychological stress on the BSTov and CEA. In Aim 1, potential changes in gene expression (immediate early genes, enkephalin, CRH, substance P or glutamic acid decarboxylase 65 and 67) that occur in the BSTov and CEA as a direct result of exposure to psychological stress will be assessed by semi-quantitative in situ hybridization. These changes could be used as an alternative independent measure in subsequent experiments. In addition, it will be determined if stress inhibition of the BSTov and CEAI generalizes to conditioned versus unconditioned stress and to corticotropin releasing hormone- (CRH) versus enkephalin-containing cells in these regions. Experiments in Aim 2 are designed to assess the neural circuitry involved in psychological stress effects on the BSTov and CEA. A combination of retrograde and anterograde tracing, dual immunohistochemistry, neurochemical lesions and glutamate injections will be used to determine if there is at least one brain region that projects to both the CEAI and the BSTov, that is activated by stress, and that is necessary and sufficient for the stress-induced gene expression changes in these brain regions. The potential role of GABA (y-amino butyric acid) in these stress-induced changes will also be assessed by determination of GABAergic inputs to the BSTov and CEAI, in vivo microdialysis for GABA during stress, and intracranial injection of GABAA and GABAC receptor antagonists into the BSTov and CEA prior to stress exposure. Ultimately, it is hoped that knowledge of the basic neural circuitry normally engaged following exposure to stress might help to identify some of the neural processes involved in the etiology of some psychiatric disorders.
|
0.958 |
2009 — 2010 |
Day, Heidi E |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Phenotypic and Functional Determination of Central Extended Amygdala Cell Groups
DESCRIPTION (provided by applicant): This proposal focuses on a brain area that is part of the central extended amygdala: the central nucleus of the amygdala (CEA). The CEA is involved in a number of responses to fear, stress and anxiety and contains distinct cell populations. However, it is not known whether the cell populations have distinct functions, and it is currently impossible to ascertain this in vivo with the tools available. This proposal aims to test the feasibility of developing a selective neurotoxic lesion of a specific neuronal population in the CEA using the neuropeptide B and W type 1 receptor (NPBW1) as a target. This receptor is very discretely expressed, specifically in the lateral CEA, but not in the surrounding areas. Furthermore, this receptor is expressed on cells of the lateral CEA that contain corticotropin releasing hormone (CRH) and dynorphin, but is not expressed on cells that contain enkephalin, or on cells of the medial CEA, a major source of amygdaloid output neurons. A selective ligand for this receptor (neuropeptide W-30) will be custom conjugated with saporin (by Advanced Targeting Systems). Aim 1 focuses on the development of an effective and selective neurotoxic lesion of the CEA. The ligand will bind to the NPBW1 receptor and when internalized will release saporin into the cell, causing the death of the cell. The utility of this approach has been shown for other receptor systems, including selective targeting of cells of the intercalated nuclei of the amygdala, using the mu opioid receptor as a target. The specificity of the localization of the NPBW1 receptor suggests that this lesioning method will selectively destroy cells containing CRH and dynorphin, but spare both enkephalin containing cells in the lateral CEA, and amygdaloid output cells within the medial CEA that are thought to be critical for modulation of several fear and anxiety responses (e.g. fear potentiated startle response). In Aim 2, the potential functions of CRH/dynorphin cells of the central extended amygdala will be assessed in adult male rats. These experiments will initially evaluate the effects of this neurotoxic lesion of the CEA on A) basal anxiety-like behaviors in the elevated plus maze and defensive withdrawal paradigm, and B) fear-potentiated acoustic startle reflexes. It is hoped that the development of a tool to selectively target a specific population of the CEA will help to define its functions, with an initial emphasis on the roles that the cells may play in fear and anxiety-like responses. It is hoped that with time, this work will ultimately lead to the development of neurotoxic lesions of several distinct cell types in the central extended amygdala, including the bed nucleus of the stria terminalis, and collectively, this will lead to a better understanding of the processing of negative emotions that are associated with the development and exacerbation of many fear and anxiety-related disorders. This proposal aims to selectively remove a specific neuronal population in the brain that is thought to be involved in stress, fear and/or anxiety responses. It is hoped that selectively targeting a specific population (rather than the more global approach currently available) will lead to a better understanding of how the brain processes these negative emotions. This in turn will be helpful in the design of treatment strategies for anxiety and fear-related disorders.
|
0.958 |