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UBC Theses and Dissertations

Fine mapping of the spatial relationship between acute ischemia and dendritic structure indicates a selective vulnerability of layer V neuronal dendritic tufts within single neurons on vivo Enright, Lauren


We have evaluated the spatial relationship between local blood flow and the structural integrity of layer 5 cortical neurons in YFP-H transgenic mice 2-10 h after stroke. Fortuitously, ischemic zones could be finely mapped with respect to dysmorphic YFP labelled axons and dendrites using histology since texas-red dextran used to measure blood flow in vivo was trapped within fixed ischemic vessels. Ischemic damage to layer 5 neurons located at the border of ischemia was contained within apical tuft dendrites and did not propagate to deeper dendrites despite the potential for diffusion of released cytotoxic factors. Dendritic damage decayed sharply with distance from the edge of ischemia (50% reduction in beaded dendrites within ~100 μm) and increased with time up to 6 h after stroke but not thereafter. Axonal damage also increased with time after the infarct but extended further laterally than dendritic damage, up to 600 μm from the stroke core. Apoptotic and necrotic cell death cascades were activated 6 h after stroke, however, only within 300 μm of the ischemic core. These data suggest that the axonal and dendritic circuitry of neurons located 300 μm outside of an ischemic zone can be relatively free of damage or commitment to cell death pathways suggesting that they may be in an ideal position to contribute to functional recovery. Given that ischemic damage may have a larger effect on circuitry involving superficial dendrites and projecting axons it is conceivable that surviving peri-infarct neurons may have unique structural and functional properties.

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