Multiple sclerosis (MS) is an autoimmune disorder characterized by demyelination of the central nervous system (CNS). In addition to its role as a neurotransmitter, serotonin also plays a role in epigenetic modifications. Recent studies have found that serotonin levels are decreased in MS for reasons that are currently unknown. This is significant because serotonin plays a role in modifying histone 3. Because serotonin is decreased, we have hypothesized that serotonylation, a post-translational modification, is decreased which leads to subsequent aberrant gene expression in MS. Using the cuprizone mouse model of MS and the APP mouse model of AD, we isolated brain tissue and looked at changes in serotonylation. Methods used to view these changes were Western Blotting, confocal imaging, and densitometry.