Alzheimer's disease (AD) is a worldwide, incurable disease, and the most common form of dementia. Numbers of cases are rising, and since its discovery the only approved medications have treated only the symptoms, not the pathological cause. With the cost to society rising, the debilitating nature of the disease and the pressure put on the family members and support network of patients, disease modifying therapies are in dire need. Current models have proven an invaluable tool with which to study certain aspects of the disease and the genetics behind it, however the lack of clinically approved medications in the last 20 years suggests new models are needed. Based on the amyloid cascade hypothesis, this thesis initially characterises two models of β-Amyloid oligomer (Aβo) induced cognitive deficits. Both models are created by ICV injection of soluble Aβo into the brain of rat. The models differ only by the molecular weight of the Aβo 1-42, one, referred to as low molecular weight (LMW) Aβo, with stable dimers, trimers and tetramers, the other, referred to as high molecular weight (HMW) Aβo, consisting of assemblies ranging from ~50 to ~150 kDa. It was found that behavioural deficits were similar between the two, with a robust object recognition deficit, but no working memory deficit. Both models also showed a deficit in the synaptic marker PSD-95; however the LMW Aβo caused a deficit in the frontal cortex, whereas the HMW Aβo caused a hippocampal deficit. The role of the cellular prion protein (PrPC) was explored, by blocking its binding to Aβo with the antibody 6D11. Interestingly the two models showed different results. The HMW Aβo deficits were completely blocked by the 6D11 application, however the LMW Aβo deficits were only partially prevented. Finally, Fasudil, a vasodilator approved in parts of Asia, was used to inhibit Rho-kinase, showing a prevention of the cognitive deficits in the HMW Aβo model. The results of this thesis show the ICV administration of Aβo to be a useful model for investigating the effects of Aβo, provides a platform with which to study the differing effects of Aβo with different oligomeric assemblies, and a model to test therapeutic strategies with relevance to AD.

<p dir="ltr">Neurodegenerative diseases are progressive, incurable conditions that affect tens of millions of people worldwide and are characterized by the aggregation of misfolded protein in the brain. Though the precise role of these amyloid aggregates in the onset and progression of these diseases is not clear at this time, there is a pressing need to understand how they form and spread in human disease. In service to these aims, I have conducted three small projects to expand knowledge in this regard. I first investigated the use of thioflavin T, a common amyloid stain, as an affinity reagent for the general purification of amyloid filaments from <i>ex vivo </i>samples, observing strong potential using a relatively simple, inexpensive magnetic bead conjugation technique. I next analyzed the formation of filaments of a truncated recombinant amyloid-beta peptide with residues 1-35, observing a new filament type formed at low pH in the wild-type sequence of this truncated peptide. Finally, I conducted structural studies on amyloid-beta(1-42) filaments prepared under different conditions consistent with traumatic brain injury to observe their effect on amyloid folding. While I found no effect of differential conditions on filament type, the low-resolution structures solved were highly consistent with aggregates found in Alzheimer’s disease patients, presenting a promising way forward for <i>in vitro</i> modeling of amyloid filaments that are true to pathology. In sum, the work here presented advances the concepts of both how amyloid aggregates from patient brains can be best prepared for structural analysis, and the factors underpinning their aggregation at the onset of neurodegenerative disease.</p>