Adaptation of the Fluid Percussion Injury Model to the Mouse

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Abstract
Fluid percussion injury (FPI) is a well-characterized experimental model of traumatic brain injury (TBI) in the rat. Many pathophysiologic consequences and mechanisms of recovery after TBI rely on neurochemical pathways that can be examined in genetically altered mice. Therefore, FPI applied to mice may be a useful experimental tool to investigate TBI at the molecular level. In the present study, we establish FPI as a viable model of TBI in the mouse by characterizing acute neurological, histopathological, and behavioral changes. Right-sided parasagittal FPI or sham treatment was administered in male C57BL/6 mice. Acute neurological evaluation revealed righting reflexes in the injured animals (p < 0.001). Deficits in spatial learning and memory were observed in the Morris water maze (MWM) 5 and 6 days after injury. A novel MWM data analysis protocol is described. The injured group (n = 18) demonstrated impaired performance in the MWM during acquisition (p < 0.05) and probe trials (p < 0.025) compared to sham animals (n = 16). At 7 days postinjury, glial fibrillary acidic protein immunohistochemistry revealed intense cortical, callosal, and hippocampal gliosis. The modified Gallyas silver degeneration stain consistently labeled cell bodies and terminals throughout the ipsilateral cortex, axons in the gray matter-white matter interface above the corpus callosum and within the corpus callosum bilaterally, and terminals and fibers in the thalamus bilaterally. Additionally, the mouse FPI model described is immediately employable in labs already using the FPI rat model with no modifications to a pre-existing FPI apparatus.