The Relationship between Functional Recovery and Reorganization of Nucleus Ambiguus Following Laryngeal Reinnervation in Rats / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Ideally, treatment for vocal cord paralysis should restore normal physiologic and dynamic movement of the vocal fold. Recently, numerous studies of laryngeal reinnervation have been designed to restore function of the paralyzed larynx. None of these approaches have been consistently successful, probably due to synkinesis and an inadequate number of regenerated axons. In previous study, we confirmed the efficacy of PEMS on the early functional recovery in rats with surgically transected and reanastomosed recurrent laryngeal nerve. In this study, the relationship between functional recovery and reorganization of nucleus ambiguus following laryngeal reinnervation in rats was evaluated by retrograde double tracing technique and electron microscope. MATERIALS AND METHOD: Transections and primary anastomosis were done on left recurrent laryngeal nerves of 86 healthy male Sprague-Dawley rats. Rats were then randomly assigned to 2 groups (the group A: stimulation with PEMS, the group B: non-stimulation with PEMS). Functionally recovered status was confirmed with laryngo-videostroboscopy and laryngeal EMG. And then, functional reorganization of laryngeal motoneuron in the nucleus ambiguus (NA) was evaluated using retrograde double tracing techniques. Morphological changes of the degeneration and regeneration processes following injury was observed by electron microscopy. RESULTS: 20 rats (63%) in group A and 5 rats (17%) in the group B showed recovery of vocal fold motion. The functional reorganization of laryngeal motor neurons in the NA was observed in the rats with functional recovery (n=8), but not in the rats without functional recovery (n=8). In the electron microscopic finding, the nerve fibers of functional recovered rats were relatively well regenerated. But the configuration of the nerve fibers of non-functionally recovered rats was markedly irregular and the total axon population was smaller than that of the recovered rats, except for some cases. CONCLUSION: This study shows that failure of functional recovery of vocal fold movement following laryngeal reinnervation is probably due to not only the misdirected reinnervation, but also the incomplete axonal regeneration.

Subdiaphragmatic vagotomy induces NADPH diaphorase in the rat dorsal motor nucleus of the vagus

Axotomy of the vagal motor neurons by cervical vagotomy induces NADPH diaphorase staining due to increased nitric oxide synthase expression in both the rat dorsal motor nucleus and nucleus ambiguous; furthermore, cerical vagotomy leads to cell death of the dorsal motor nucleus cells. Subdiaphragmatic vagotomy axotomizes the vagal motor cells further from the brainstem than cervical vagotomy, and cuts the fibers running only to the abdominal viscera. Here we report that subdiaphragmatic vagotomy is sufficient to induce NADPH diaphorase staining in the dorsal motor nucleus but does not induce staining in the nucleus ambiguus. Because the neurons of the dorsal motor nucleus do not undergo cell death after subdiaphragmatic vagotomy and are able to re-enervate the gut, the increased nitric oxide synthase expression after distal axotomy may be related more to regeneration than degeneration.

Localization of Motor Neuronal Cell Bodies Innervating Heart in the Cat Using CTB as Neuronal Tracer / 체질인류학회지

The origin of motor neuronal cell bodies innervating heart in the cat was investigated using CTB (Cholera toxin B subunit) as neuronal tracer. The neural tracer was injected into subepicardial layer and myocardium of the right atrium, left atrium, right ventricle and left ventricle, respectively. Labeled parasympathetic motor neuronal cell bodies were found in DMV (dorsal motor nucleus of vagus nerve) and anterolateral part of NA (nucleus ambiguus) of brainstem. Heavier labeled neuronal cell bodies were found in the NA when the neural tracers were injected into left ventricle and DMV when injected into left atrium and left ventricle. These results may provide a neuroanatomical data on origin of motor neuronal cell bodies innervating the heart of the cat.