The Journal of Neuroscience, February 1, 2002, 22(3):791-802
Traumatically Induced Axotomy Adjacent to the Soma Does Not
Result in Acute Neuronal Death
Richard H.
Singleton1,
Jiepei
Zhu2,
James R.
Stone3, and
John T.
Povlishock1
Departments of 1 Anatomy and
2 Anesthesiology, Medical College of Virginia Campus,
Virginia Commonwealth University, Richmond, Virginia 23298, and
3 Department of Neurological Surgery, University of
Virginia, Charlottesville, Virginia 22904
Traumatic axonal injury (TAI), a consequence of traumatic brain
injury (TBI), results from progressive pathologic processes initiated
at the time of injury. Studies attempting to characterize the pathology
associated with TAI have not succeeded in following damaged and/or
disconnected axonal segments back to their individual neuronal somata
to determine their fate. To address this issue, 71 adult male Sprague
Dawley rats were subjected to moderate central fluid percussion injury
and killed between 30 min and 7 d after injury. Antibodies to the
C terminus of
-amyloid precursor protein (APP) identified TAI in
continuity with individual neuronal somata in the mediodorsal
neocortex, the hilus of the dentate gyrus, and the dorsolateral
thalamus. These somata were followed with immunocytochemical markers of
neuronal injury targeting phosphorylated 200 kDa neurofilaments
(RMO-24), altered protein translation (phosphorylated eukaryotic
translation initiation factor 2
), and cell death [terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)], with parallel electron microscopic (EM) assessment. Despite the finding
of TAI within 20-50 µm of the soma, no evidence of cell death, long
associated with proximal axotomy, was seen via TUNEL or routine light
microscopy/electron microscopy. Rather, there was rapid onset
(<6 hr after injury) subcellular change associated with impaired
protein synthesis identified by EM, immunocytochemical, and Western
blot analyses. When followed 7 d after injury, these abnormalities
did not reveal dramatic progression. Rather, some somata showed
evidence of potential reorganization and repair. This study
demonstrates a novel somatic response to TAI in the perisomatic domain
and also provides insight into the multifaceted pathology associated
with TBI.
Key words:
traumatic brain injury; traumatic axonal injury; axotomy; axon reaction; rat; protein translation; TUNEL
Copyright © 2002 Society for Neuroscience 0270-6474/02/223791-12$05.00/0