Regenerative process of the facial nerve: rate of regeneration of fibers and their bifurcations.
After the main trunk of the mouse facial nerve was injured by crushing, a fiber tracing method was used to quantify the facial motor neurons that extended regenerating nerve fibers to the specific site of the facial nerve branch. The total number of motor neurons retrogradely labeled with a fluorescent tracer, Fluoro-Gold (FG), were 0 on postsurgical days (PSDs) 1 and 2, 75+/-25 on PSD3, 264+/-21 on PSD4, 378+/-19 on PSD6, 428+/-19 on PSD8, 491+/-13 on PSD12 and 532+/-15 on PSD16. Assuming that the FG-positive neurons (535+/-11) of the control mice represent 100%, the FG-labeled neurons accounted for 0, 14, 49, 71, 80, 92 and 99% on the corresponding days. Two different fluorescent tracers were applied to the different facial nerve branches 16 days after facial nerve injuries. Double-labeled neurons were consistently found in the nerve-crushed facial nucleus (3.2%), and their number increased in the nerve-transected facial nucleus (12.2%). The present study indicates that the regenerating facial nerve consists of heterogeneous nerve fibers with varying growth rates and that excessive axonal branching occurs more frequently in the nerve-transected than in the nerve-crushed injuries.
Kamijo
Y
Y
Department of Anatomy, Shinshu University School of Medicine, Matsumoto 390-8621, Japan.
Koyama
J
J
Oikawa
S
S
Koizumi
Y
Y
Yokouchi
K
K
Fukushima
N
N
Moriizumi
T
T
D000818:Animals; D019771:Axotomy; D002470:Cell Survival; D005154:Facial Nerve / Q000502:physiology*; D020220:Facial Nerve Injuries / Q000473:pathology / Q000503:physiopathology*; D005456:Fluorescent Dyes; D008297:Male; D051379:Mice; D009046:Motor Neurons / Q000473:pathology / Q000502:physiology; D009409:Nerve Crush; D009416:Nerve Regeneration / Q000502:physiology*; D020127:Recovery of Function; D013266:Stilbamidines; D013997:Time Factors; D014738:Vibrissae / Q000294:innervation
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D013266:Stilbamidines