This application for renewal of an R01 grant proposes to expand on promising leads developed during initial support. One set of questions followed from an hypothesis (reviewed below) that AMPA/kainate-type glutamate receptor activation might contribute to slow neurodegeneration in Alzheimer's disease (AD). The project has thus sought to further examine potential connections between AMPA/kainate receptors and AD by examining the vulnerability of basal forebrain cholinergic neurons, which degenerate in AD, and by elucidating the basis for the selective vulnerability of certain neuronal populations to AMPA/kainate receptor-mediated injury (most of these studies focused on one such vulnerable population, that marked by possession of high concentration of the enzyme NADPH-diaphorase; NADPH-d(+) neurons). Another question concerned clarification of the relationship between the role of Ca2+ entry, and that of nitric oxide (NO) (produced largely in NADPH-d(+) cells) in mediating glutamate injury. Many of these questions have been answered in less than 2 years on the project, and the aims and goals have been mildly modified in light of recent results (as discussed in detail in the progress report). This project will continue to use nerve cell cultures to examine certain questions about selective neuronal vulnerability; We have found cortical somatostatin, parvalbumin, and recently basal forebrain cholinergic neurons (all of which may preferentially degenerate in AD) to be exceptionally vulnerable to AMPA/kainate receptor-mediated injury. Pyramidal neurons, which degenerate in AD, will be examined to determine whether they share this unusual AMPA/kainate vulnerability. Additional studies will examine the hypothesis that Ca2+ entry is central tot he injury. Neurotoxicity, 45Ca2+ influx, and fluorescent Ca2+ imaging techniques will be employed to determine the relationship between routes and amounts of agonist triggered Ca2+ entry, neuronal Ca2+ homeostatic mechanisms, and selective vulnerability of neuronal subpopulations. Finally studies will be carried out to explore possible synergism between endogenous factors (such as beta-amyloid peptide, Zn2+ or metabolic/oxidative stress) and AMPA/kainate receptor activation in producing selective injury, and to examine mechanisms downstream from Ca2+ entry (including nitric oxide production) that may contribute to the injury).
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