Hippocampal neuronal degeneration in the traumatic brain injury mouse: non-trivial effect of scalp incision.
OBJECTIVE
In experimental models of traumatic brain injury (TBI), posttraumatic hippocampal neuronal degeneration in the cornu ammonis 1 (CA1), and/or the cornu ammonis 3 (CA3) regions are regarded as the most notable phenotypic appearances relating to the pathophysiology of human post-concussion syndrome. However, these morphological changes are often also seen in subjects without TBI, namely 'sham' groups. The frequencies and reasons of appearance of hippocampal neuronal degeneration in mice with TBI and/or sham are not clear.


METHODS
We compared the frequencies of hippocampal neuronal degeneration among three groups: TBI (mice with external force impact performed by Marmarou's weight drop model after scalp incision), sham (mice with scalp incision alone), and control (mice with neither external force impact nor scalp incision), using hematoxylin and eosin stain in day 6 (n = 5 in each group.) Isoflurane was used for anesthesia in all mice.


RESULTS
The frequencies were 80, 100, and 20% in CA1, and 20, 40, and 60% in CA3, for TBI, sham, and control, respectively. In CA1, a significant difference of the frequency was observed between sham and control (p = 0.048), but not, between TBI and sham (p = 1.000) in Fisher's exact test. In CA3, no significant difference in the frequency was observed between the three groups.


CONCLUSIONS
Scalp incision, rather than external impact force, might affect the CA1 hippocampal neuronal degeneration in mice with TBI. In addition, factor(s) other than external impact force or scalp incision may also cause hippocampal neuronal degeneration in both CA1 and CA3. Careful interpretation is needed concerning hippocampal neuronal degeneration induced by a weight drop device observed in mice with TBI.
a Department of Legal Medicine , School of Medicine, Tokyo Women's Medical University , Tokyo , Japan.
Jiro
J
Ezaki
a Department of Legal Medicine , School of Medicine, Tokyo Women's Medical University , Tokyo , Japan.
Ryo
R
Shimada
a Department of Legal Medicine , School of Medicine, Tokyo Women's Medical University , Tokyo , Japan.
Misato
M
Shibuya
a Department of Legal Medicine , School of Medicine, Tokyo Women's Medical University , Tokyo , Japan.
Kazuhiko
K
Kibayashi
D000818:Animals; D000070642:Brain Injuries, Traumatic / Q000150:complications*; D002452:Cell Count; D004195:Disease Models, Animal; D006624:Hippocampus / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019636:Neurodegenerative Diseases / Q000209:etiology* / Q000473:pathology*; D009474:Neurons / Q000145:classification / Q000473:pathology*
Hippocampus; Neuronal degeneration; Scalp incision; Traumatic brain injury; Weight drop