Concussive Brain Injuries

Concussive brain injuries (CBI) affect cognitive functions such as working and spatial memory, impaired attention and information processing. CBIs also cause traumatic axonal injury (TAI), leading to abnormal axon function. Cognitive deficits usually resolve fairly quickly, however, the brain continues to have structural and functional damage for weeks or even years. This study developed a CBI model in mice by striking the exposed skull with a metal device along the midline suture between lambda and bregma. Deficits in spatial and working were observed using a Morris water maze. The cortical area under the impact site had signs of edema (wet dry weight ratio) and also Fluro-Jade-B positive cells indicating neuronal degeneration.

Concussive Brain Trauma in the Mouse Results in Acute Cognitive Deficits and Sustained Impairment of Axonal FunctionJennifer A. Creed, Ann Mae DiLeonardi, Douglas P. Fox, Alan R. Tessler, and Ramesh Raghupathi

Morris Water Maze

Traumatic Axonal Injury

Concussive Brain Injuries

Fluro-Jade-B positive cells were also found in the dentate gyrus of the hippocampus. Corpus callosum axonal swelling was observed as β- amyloid precursor protein (β-APP) and dephosphorylated neurofilaments in axons as well as in retraction bulbs, indicating TAI. Cognitive deficits, edema, neuronal degeneration, and TAI were only significant in the first 3 days port-injury. At 14 days after injury, degenerating axons were seen in the corpus callosum, meaning that axons continue to degrade after injury. This is possibly a result of the build-up of β-APP and dephosphorylated neurofilaments during the acute period after injury. Also at 14 days post-injury, reduced amplitudes of action potential recorded with microelectrodes in the corpus callosum of injured mice were observed as well as decreased retrograde transport in axons. This model could be used to understand the mechanism of TAI after CBI and treatment development.

Fluro-Jade-B

Retraction Bulbs

References •Concussive Brain Trauma in the Mouse Results in Acute Cognitive Deficits and Sustained Impairment of Axonal Function: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3070143/pdf/neu.2010.1729.pdf•Concussions 101 video: http://www.youtube.com/watch?v=zCCD52Pty4A#t=152•Image of axon shearing: http://www.seeyouincourt.com/practice-areas/traumatic-brain-injuries-tbi/•DTI of axonal injury: http://braininjuryhelp.com/dti-diffusion-tensor-imaging-mri/•Fluoro-Jade B: a high affinity fluorescent marker for the localization of neuronal degeneration: http://www.sciencedirect.com/science/article/pii/S0006899300025130•Fluoro-Jade B stain picture: http://www.biosensis.com/fluoro-jade-ready-dilute-staining-identifying-degenerating-neurons-p-1171.html•Black and white Fluro-jade B stain and retraction ball pictures: from article figures•Disorganized Microtubules Underlie the Formation of Retraction Bulbs and the Failure of Axonal Regeneration: http://www.jneurosci.org/content/27/34/9169.long•Morris water maze videos: http://www.youtube.com/watch?v=ScfOE1qMIFY . http://www.youtube.com/watch?v=2k-PkRjr_DY