Several properties of central cholinergic and dopaminergic neurons appear to be regulated in part by trophic factors originating from their target tissues. We propose to purify four of these factors and characterize their biological and chemical properties, using neuron-rich cultures of rat central neurons to assay trophic factor effects. In particular, we will study: (1) a factor made by muscle which enhances acetylcholine synthesis in spinal cord cultures, (2) a factor isolated from the neocortex which enhances acetylcholine synthesis and cholineacetyltransferase activity in cultures of rat basal forebrain cells. The activity of this factor is not blocked by antibodies against the classical nerve growth factor, and this factor does not affect spinal cord neurons. (3) a factor from the striatum which enhances dopamine synthesis in cultures of basal mesencephalon (includes substantia nigra) neurons, and (4) a serum-derived factor which greatly enhances the survival of both cholinergic and dopaminergic neurons. Bioassays will be used to follow the trophic activity through biochemical separation procedures. Immunological methods will be used to facilitate the final purification steps and obtain blocking antibodies to help in studying the biological functions of the factors. Purified trophic factor preparations will be tested to determine the range of their effects on target neurons (enhancement of transmitter synthesis, neurite outgrowth, ability to regenerate processes following trauma, and effects on cell survival, protein synthesis and electrophysiological membrane properties). We will also determine whether the trophic actions are reversible and modulatory, or irreversible and perhaps stage-specific. We plan also to extend these trophic factor studies to cultured primate neurons to determine whether the factors that are trophic for rat neurons also have similar actions on primate neurons, and whether primate tissues make similar trophic factors. Using fractions of serum from patients with neurodegenerative diseases affecting the brain regions we culture (amyotrophic lateral sclerosis, Parkinson's disease, Alzheimer's disease), we will test claims of specific neurotoxic serum factors, and determine whether these patients might have antibodies against the trophic factors and their receptors.
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