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beta-Amyloid precursor protein immunoreactivity (APP) was studied after a mild compression contusion trauma to rat parietal cortex. Neurones in the periphery of the cortical lesion, i.e. tissue subjected to shear stress, showed markedly reduced immunoreactivity 1 and 3 days after injury. Numerous axons in the ipsilateral subcortical white matter and thalamus became immunoreactive. At 21 days, small rounded profiles appeared in the neuropil of the damaged cortex and in the thalamus. Thus, traumatic brain injury appears to induce several types of APP changes. The accumulation in neuronal processes is probably caused by disturbed axonal transport induced by trauma. Since APP is assumed to be excitoprotective, modulating intracellular Ca2+ responses, the decreased immunoreactivity noticed in the periphery of the lesion may render the neurones in this region more vulnerable to secondary injury mechanisms.
Lewén et al. (Sun,) studied this question.