Abstract
Soluble oligomers of human amyloid beta (Aβ) have been implicated in the pathophysiology of Alzheimer’s Disease (AD). Applications of dimeric and globular-oligomeric human Aβ1-42 via perfusions in artificial cerebral spinal fluid (aCSF) to slices of rat hippocamppi have consistently resulted in early and late LTP decreases in CA1 relative to vehicular controls, as measured by electrophysiological field excitatory postsynaptic potential (fEPSP) recordings (Selkoe, 2008). A current theory explaining LTP in CA1 synapses of hippocamppi is that calcium influx initiates a signal transduction pathway that activates the catalytic domain of Ca2+/calmodulin-dependent protein kinase (CaMKII), which then translocates to the synapse and facilitates LTP (Lisman et al., 2012). Several studies have suggested a role of CaMKII in cognitive dysfunction during AD (Ly and Song, 2011). However, this role is unclear, as is how CaMKII activity is affected by Aβ. In addition, many studies testing the neurodegenerative effects of Aβ have not identified the biochemical states of the peptide. In this thesis, novel methods were developed that consistently produced both dimers and globular oligomers in high relative concentrations from synthetic Aβ1-42. Western Blot was used to characterize the Aβ preparations. Field EPSP recordings of CA1 in acute slices of rat hippocamppi perfused with aCSF demonstrated that the LTP induction protocol indeed induced LTP in the rat model in the absence of both Aβ and vehicle. Preliminary Fluorescence Resonance Energy Transfer (FRET) lifetime measurements with Camui quantified the activation levels of dendritic CaMKII under basal conditions in the presence of prepared Aβ. The FRET signal decreased gradually at three (3) dendritic locations under basal conditions during Aβ application (Figure 21), indicating activation of CaMKII in response to Aβ. In summary, potentially neurotoxic species of Aβ were produced that may be used to probe potential downstream targets of Aβ, as well as to test the effects of anti-AD chemotherapeutic agents.