Analysis of spontaneous regeneration of olfactory structures with emphasis on myelination and re-innervation of cortical areas.
Regeneration of the lateral olfactory tract (LOT) occurs spontaneously after transection in developing rats. In neonatally LOT-transected rats, we observed a newly formed myelinated tract near the rhinal sulcus. The aim of this study was to analyze the precise re-innervated cortical areas and to demonstrate ectopic LOT myelination in neonatally LOT-transected rats. Neonatal rats were subjected to unilateral LOT transection and simultaneous injection of a retrograde fluorescent tracer into the posterior olfactory cortex to evaluate the degree of transection. After 8 weeks, bilateral olfactory bulbs of the rats were subjected to multiple injections of an anterograde neuronal tracer to determine the extent of the regenerated fibers. In the completely LOT-transected rats, the regenerated fibers were distributed in the anterior olfactory cortices; the anterior olfactory nucleus, the olfactory tubercle, and the rostral part of the piriform cortex. Ectopic myelination of LOT was evident immediately below the rhinal sulcus in the completely and incompletely LOT-transected rats. We concluded that the regenerated bulbar fibers were confined to the regions of the anterior olfactory cortices and that ectopic myelination of the regenerated LOT occurred only at a specific site near the rhinal sulcus.
Department of Anatomy, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan. nanae@shinshu-u.ac.jp
Nanae
N
Fukushima
Kumiko
K
Yokouchi
Michio
M
Sakamoto
Yasuyuki
Y
Sekiguchi
Hiroki
H
Koike
Kyutaro
K
Kawagishi
Tetsuji
T
Moriizumi
D000818:Animals; D000831:Animals, Newborn; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D005260:Female; D008297:Male; D009186:Myelin Sheath / Q000378:metabolism*; D009413:Nerve Fibers, Myelinated / Q000378:metabolism; D009830:Olfactory Bulb / Q000502:physiology; D009833:Olfactory Pathways / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar