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.
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.
