Whole Brain Irradiation and its Effects on Spatial Memory in Fisher-344 Rats
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The idea of synaptic plasticity is that the connection of each synapse within a neural network can constantly change due to various factors that can either strengthen or weaken it. The genes that underlie the stabilization of this synaptic plasticity have been identified as immediate early genes (IEGs) due to their rapid induction during activity dependent plasticity. IEGs are induced in hippocampal neurons by high frequency electrical stimulation, which results in induction of an electrophysiological process of long-term potentiation (LTP). They can also be induced by behavioral training, which results in long-term memory (LTM) formation. The IEG protein of interest for this study was Arc (activity-regulated cytoskeleton associated protein). We sought to observe Arc and its role in hippocampal plasticity both in the presence and the absence of whole brain irradiation (WBI) at 12Gy using LTP, the Morris Water Maze as a spatial behavioral assay, and lastly protein analysis staining to quantify Arc protein expression. Our results show that WBI caused a reduction in amplitude and slope for EPSP corresponding to the maintenance phase of LTP. In the behavioral assay there was no significant difference found between control and irradiation treatments in terms of latency to escape, amount of time spent in the NE quadrant and platform crossings. And lastly, upon protein staining analysis it was found that WBI effectively inhibited any Arc protein expression within the dentate gyrus. This kind of radiation biology research provides a notable model of the longitudinal effects of the irradiation treatments being used for cancer today. Knowing more about WBI can avoid such harsh side effects for many who receive the current treatment experience; from hair loss to impairment of cognitive function.