Nimodipine improves reinnervation and neuromuscular function after injury to the recurrent laryngeal nerve in the rat.
OBJECTIVE
Injury of the recurrent laryngeal nerve (RLN) is associated with a high degree of neuronal survival, but leads to various levels of vocal fold motion impairment or laryngeal synkinesis, which has been attributed to misdirected reinnervation of the target muscles in the larynx or aberrant, competing reinnervation from adjacent nerve fibers. The aim of the present study was to evaluate the impact of the regeneration-promoting agent nimodipine on reinnervation and neuromuscular function following RLN crush injury.


METHODS
Sixty adult rats were randomized into nimodipine-treated or untreated groups and then underwent RLN crush injury. Reinnervation of the posterior cricoarytenoid muscle (PCA) was assessed by electrophysiological examination, retrograde tracing of lower motor neurons before and after injury, and quantification of neuromuscular junctions in the PCA muscle.


RESULTS
At 6 weeks after injury, the nimodipine-treated animals showed significantly enhanced neuromuscular function and also demonstrated a higher number of motor neurons in the brain stem that had reinnervated the PCA, compared to the untreated animals. The somatotopic organization of ambiguus motor neurons innervating the larynx was similar before injury and after reinnervation.


CONCLUSIONS
Nimodipine improves regeneration and neuromuscular function following RLN injury in the adult rat, and could be of use in future strategies following RLN injury.
Hydman
Jonas
J
Department of Clinical Neuroscience, Section of Neurosurgery, Karolinska University Hospital, Stockholm, Sweden.
Remahl
Sten
S
Björck
Gunnar
G
Svensson
Mikael
M
Mattsson
Per
P
D000818:Animals; D001933:Brain Stem / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004576:Electromyography; D005260:Female; D007821:Laryngeal Muscles / Q000294:innervation*; D009046:Motor Neurons / Q000187:drug effects; D009409:Nerve Crush; D009416:Nerve Regeneration / Q000187:drug effects*; D009469:Neuromuscular Junction / Q000187:drug effects; D009553:Nimodipine / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D012009:Recurrent Laryngeal Nerve / Q000187:drug effects; D061226:Recurrent Laryngeal Nerve Injuries; D014827:Vocal Cords / Q000294:innervation
D009553:Nimodipine