Ionotropic glutamate receptors (iGluR s) have been extensively implicated in triggering neuronal cell death, and have subsequently been related to a multitude of neurodegenerative disease processes. It had been hoped that antagonists of these receptors might be useful therapeutic tools, but their use has proved to be problematic for multiple reasons. The role of metabotropic glutamate receptors (mGluR s) in the process of neuronal cell death has been receiving increasing amounts of attention over the last several years. Recent literature suggests that mGluR's can indeed effect progression towards cell death, but how they do so is complicated by variations in how the different mGluR subtypes function, confounding effects due to mGluR-iGluR interactions, and by the prior lack of subtype-specific agonists and antagonists. Though progress has been made towards investigating the involvement of mGluR's in neuronal degeneration, the nature of this involvement, as well as which mechanisms are responsible for it, remain to be delineated. In addressing our hypotheses, our overall approach would therefore be to compare: 1). Hippocampal vs. cerebellar Purkinje cell cultures. Because these cell types express different patterns of mGluR and iGluR receptors, different mGluR-iGluR interactions can be compared, contrasted, and limited to those that are physiologically important. 2). Necrotic vs. Apoptotic cell death. These two pathways apparently represent different metabolic reactions to toxic insults. Since mGluR receptors may exert their effects via either or both pathways, comparing the two may shed light on how mGluR's influence the process of neurodegeneration. We propose the following investigations: 1). To assess the conditions under which excitotoxicity might be influenced by mGluR s, cells would be treated with agonists of the 3 mGluR classes alone or in combination with iGluR agonists. The amount of necrosis or apoptosis present would then be evaluated. 2). The influence of mGluR agonists on iGluR-induced calcium fluxes will be examined using digital video microfluorimetry and the dye Fura-2 AM. 3). The influence of mGluR agonists on iGluR-induced mitochondrial calcium and membrane potential changes will be examined using digital video microfluorimetry and the mitochondrial dyes tetramethylrhodamine and dihydro rhod-2 AM. In addition, the effect of the mGluR agonists on non-calcium related mitochondrial changes (induced with ruthenium red and FCCP) will also be examined.