Nimodipine Improves Reinnervation and Neuromuscular Function after Injury to the Recurrent Laryngeal Nerve in the Rat

Abstract

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. 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. 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. Nimodipine improves regeneration and neuromuscular function following RLN injury in the adult rat, and could be of use in future strategies following RLN injury.