DESCRIPTION (Investigator's Abstract): Beta/A4-containing amyloid accumulation plays a crucial role in the [pathogenesis] of Alzheimer disease (AD) and a rapid model to study the effect of amyloid [persistence] in brain is needed. The present proposal offers a rapid and novel means of generating an animal model [to study effects of congophilic and fibrillar] Beta/A4 amyloid in brain, In our model, 1 or 2 week co--infusions of Beta/A4 peptide plus heparan sulfate proteoglycan (HSPG) directly into rat hippocampus is sufficient for the successful rapid deposition [and persistence] of conogophilic Beta/ A4- containing amyloid in brain in [15 of 15]animals tested [Infusion of only Beta/A4 resulted in less than 50% (7 of 15) of animals demonstrating congophilic and fibrillar Beta/A4, amyloid in brain. A significance difference (p<:0.01) in congo red staining (an indicator of fibrillar amyloid) was observed between rats infused with Beta/A4 plus HSPG, versus those infused with Beta/A4 alone, indicating that inclusion of HSPG in the infusate was essential for consistent amyloid persistence in brain using this model]. Specific Aim #1 will [further] optimize the procedure for Beta/A4 amyloid deposition, and determine the specificity of reagents necessary for deposition. These experiments will compare different Beta/A4 peptides, and/or other PG's for their capacity to support congophilic amyloid formation. The optimal concentrations of these agents and the minimum period for amyloid formation will be determined. Detection of amyloid deposition will be evaluated by specific stains and immunocytochemical probes. Electron microscopy will determine the nature of amyloid formed and this precise location. [We will also evaluate the in vitro interaction of infusate components by negative stain electron microscopy, Congo red staining, and silver staining following SDS-PAGE electrophoresis]. Specific Aim #2 will examine the long term anatomical and molecular consequences of amyloid [persistence]. A time course study ranging from 2 weeks to 1 year will be performed. Immunocytochemical, histological and in situ hybridization probes will evaluate the capacity of Beta/A4 amyloid to induce changes in the brain which resemble those of AD. Success in these aims should provide valuable information on the influence of Beta/A4 amyloid deposition of the structure, function and regulation of macromolecules within the brain.