Thinning, movement, and volume loss of residual cortical tissue occurs after stroke in the adult rat as identified by histological and magnetic resonance imaging analysis

Abstract

Plasticity of residual cortical tissue has been identified as an important mediator of functional post-stroke recovery. After neonatal stroke the thickness of residual tissue can change, the tissue can move, and tissue can fill in the stroke core. Nevertheless, the majority of preclinical stroke research utilizes adult rats. Thus, the purpose of the present thesis was to systematically document such gross morphological changes in peri-infarct tissue after stroke in the adult rat. Morphological changes were assessed in pial strip devascularization, photothrombotic occlusion, and middle cerebral artery occlusion models of stroke using histological and magnetic resonance imaging. Decreases in cortical thickness, volume, and neural density were found to extend far beyond the stroke infarct and included the sensorimotor regions of the intact hemisphere. Movement of residual tissue towards the infarct was observed and confirmed using anatomical markers placed in intact cortical tissue at the time of stroke induction. I conclude that the extensive time-dependent morphological changes that occur in residual cortical tissue must be considered when evaluating plasticity-related cortical changes associated with post-stroke recovery of function.