Morphology of nerve endings in vocal fold of human newborn.

Sensory receptors are distributed throughout the oral cavity, pharynx, and larynx. Laryngeal sensitivity is crucial for maintaining safe swallowing, thus avoiding silent aspiration. Morphologic description of different receptor types present in larynx vary because of the study of many different species, from mouse to humans. The most commonly sensory structures described in laryngeal mucosa are free nerve endings, taste buds, muscle spindles, glomerular and corpuscular receptors. This study aimed at describing the morphology and the distribution of nerve endings in premature newborn glottic region. Transversal serial frozen sections of the whole vocal folds of three newborns were analyzed using an immuno-histochemical process with a pan-neuronal marker anti-protein gene product 9.5 (PGP 9.5). Imaging was done using a confocal laser microscope. Nerve fiber density in vocal cord was calculated using panoramic images in software Morphometric Analysis System v1.0. Some sensory structures, i.e. glomerular endings and intraepithelial free nerve endings were found in the vocal cord mucosa. Muscle spindles, complex nerve endings (Meissner-like, spherical, rectangular and growing) spiral-wharves nerve structures were identified in larynx intrinsic muscles. Nervous total mean density in vocal cord was similar in the three newborns, although they had different gestational age. The mean nerve fiber density was higher in the posterior region than anterior region of vocal cord. The present results demonstrate the occurrence of different morphotypes of sensory corpuscles and nerve endings premature newborn glottic region and provide information on their sensory systems.

Afferent nerve ending density in the human laryngeal mucosa: potential implications on endoscopic evaluation of laryngeal sensitivity.

Laryngeal sensitivity is crucial for maintaining safe swallowing, thus avoiding silent aspiration. The sensitivity test, carried out by fiberoptic endoscopic examination of swallowing, plays an important role in the assessment of dysphagic patients. The ventricular folds appear to be more sensitive than the epiglottis during the sensitivity test. Therefore, this study aimed to investigate the mechanical sensitivity of the supraglottic larynx. In seven healthy adults undergoing microlaryngoscopy to remove vocal cord polyps, we excised mucosal samples from the epiglottis and ventricular folds. We measured afferent nerve fiber density by immunoelectron microscopy. All of the subjects underwent an endoscopic sensitivity test based on lightly touching the laryngeal surface of the epiglottis and ventricular folds. The discomfort level was self-rated by the subjects on the visual analog scale. Samples were fixed and stored in cryoprotectant solution at 4 °C. Sections were stained with the protein gene product 9.5, a pan-neuronal selective marker. Nerve fiber density was calculated as the number of fibers per millimeter length of section. The mean nerve fiber density was higher in ventricular samples than in epiglottis samples (2.96 ± 2.05 vs 0.83 ± 0.51; two-sided p = 0.018). The mean visual analog scale scores were significantly higher for touching the ventricular folds than for touching the epiglottis (8.28 ± 1.11 vs 4.14 ± 1.21; two-sided p = 0.017). The higher sensitivity of the ventricular region should be considered for further refining clinical endoscopic evaluation of laryngeal sensitivity.

Lesion of the nucleus solitarius leads to impaired laryngeal sensation in bulbar palsy patients.

BACKGROUND: In order to clarify the laryngeal sensation of bulbar palsy patients, we studied the relationship between laryngopharyngeal sensation and brainstem lesion in patients with dysphagia caused by bulbar palsy. METHODS: Fifteen patients with lateral medullary infarction and dysphagia were included in this study. We performed laryngeal sensory test using the flexible laryngoscope and probes method previously developed by Yaguchi et al. The test sites included the right and left tip of the laryngeal surface of the epiglottis and bilateral arytenoid regions. Lesion sites were identified by magnetic resonance imaging and classified horizontally according to Kim's classification. We also used the anatomical atlas Cytoarchitecture of the Human Brain Stem to determine whether the lesions included the nucleus solitarius and nucleus ambiguus. RESULTS: Eight cases had normal sensation and 7 cases had decreased sensation of the affected side of the epiglottis and arytenoid region. The lesions of decreased laryngeal sensation group were classified horizontally as large type or dorsal type and included the nucleus solitarius. Decreased laryngeal sensation was significantly correlated with lesions that included the nucleus solitarius (Fisher exact test; P = .026). CONCLUSIONS: This study clarifies that patients with dysphagia caused by bulbar palsy may present with laryngeal sensory impairment of the affected side and laryngopharyngeal movement disorder. The important finding is that damage to both the nucleus solitarius and ambiguus cause dysphagia accompanied by decreased laryngeal sensation and that the lesions are relatively extensive and affect the middle level of the dorsal medulla.

Morphological development and expression of neurotrophin receptors in the laryngeal sensory corpuscles.

Morphological development of sensory structures in the laryngeal mucosa of postnatal rats was observed by use of immunohistochemistry for protein gene-product 9.5 (PGP9.5). Moreover, expression changes of high affinity neurotrophin receptors, TrkA, TrkB and TrkC, and low affinity neurotrophin receptor p75(NTR) were examined to elucidate the relationship to morphogenesis. Intraepithelial nerve endings and parent axons of the laminar endings with immunoreactivity for PGP9.5 have already appeared in the rat on embryonic day 18 (E18) as well as solitary chemoreceptor cells in the glottic cleft. According to neurotrophin receptors, TrkA immunoreactivity were observed on and after postnatal week 3 (3W) in the nervous sensory structures, that is, free nerve endings, laminar endings and sub- and intragemmal plexuses of the taste buds. In the laminar endings, TrkC immunoreactivity was also observed on and after 3W. According to the laryngeal sensory cells, the solitary chemoreceptor cells were immunoreactive to TrkA, TrkB, and TrkC on and after postnatal day 3 (P3). In the taste buds in arytenoid region, taste cells were immunoreactive for TrkA, TrkB, and TrkC on and after 3W, P14, and 3W, respectively. Immunoreactivity for p75(NTR) was observed on the surface of taste cells on and after P9. The results of the present study suggest that sensory structures in the laryngeal mucosa were developed on perinatal days to involve respiratory reflex, and that neurotrophin receptors may take part in the regulation and maintenance of sensory structures.

Submucosal nerve hypertrophy in congenital laryngomalacia.

OBJECTIVES/HYPOTHESIS: To determine the neuropathologic findings in tissue obtained from children with laryngomalacia at a tertiary-care pediatric hospital. STUDY DESIGN: Retrospective review of consecutive cohort compared with a control group. METHODS: We reviewed supra-arytenoid pathology specimens from 43 children with severe laryngomalacia and 13 age-matched pediatric autopsy controls. Histopathologic comparison was made of nerve hypertrophy (including nerve perimeter and surface area) among experimental and control pathologic specimens. RESULTS: There exists a statistically significant increase in nerve perimeter (P = .001) and nerve surface area (P = .02) in supra-arytenoid specimens in patients with severe laryngomalacia compared with age-matched autopsy supra-arytenoid tissue. CONCLUSIONS: The pathologic finding of nerve hypertrophy in children with laryngomalacia provides new evidence to support neurologic dysfunction as the etiologic theory of laryngomalacia.

Expression of ENaC subunits in sensory nerve endings in the rat larynx.

We investigated the expression of three subunits of epithelial sodium channel (ENaC), alphaENaC, betaENaC and gammaENaC, in the nodose ganglion and laryngeal mucosa of rat by RT-PCR analysis and immunohistochemistry. PCR products of predicted size for alphaENaC, betaENaC and gammaENaC subunits were amplified from extract of nodose ganglion. Immunohistochemically, nodose ganglion neurons of medium to large diameter were immunoreactive for alphaENaC, betaENaC and gammaENaC. In the deep region of laryngeal submucosal layer, thick nerve fibers without varicosities were immunoreactive for alphaENaC, betaENaC and gammaENaC. In the laryngeal mucosa, terminal arborizations of the nerve endings, that immunoreacted for alphaENaC, betaENaC and gammaENaC were scattered in the lamina propria just beneath the epithelia of epiglottis and laryngeal vestibule. Double immunofluorescence with calretinin revealed that they were laminar nerve endings. Some thick nerve fibers near the laryngeal taste buds were also immunoreactive for betaENaC and gammaENaC, but negative for alphaENaC. In the larynx, ENaC channels may play important roles in mechanotransduction in the laminar endings and in the mechano- and chemotransductions in the taste bud-associated nerve fibers.

Laryngeal chemosensory clusters.

The expression of molecules involved in the transductory cascade of the sense of taste (TRs, alpha-gustducin, PLCbeta2, IP3R3) has been described in lingual taste buds or in solitary chemoreceptor cells located in different organs. At the laryngeal inlet, immunocytochemical staining at the light and electron microscope levels revealed that alpha-gustducin and PLCbeta2 are mainly localized in chemosensory clusters (CCs), which are multicellular organizations differing from taste buds, being generally composed of two or three chemoreceptor cells. Compared with lingual taste buds, CCs are lower in height and smaller in diameter. In laryngeal CCs, immunocytochemistry using the two antibodies identified a similar cell type which appears rather unlike the alpha-gustducin-immunoreactive (IR) and PLCbeta2-IR cells visible in lingual taste buds. The laryngeal IR cells are shorter than the lingual ones, with poorly developed basal processes and their apical process is shorter and thicker. Some cells show a flask-like shape due to the presence of a large body and the absence of basal processes. CCs lack pores and their delimitation from the surrounding epithelium is poorly evident. The demonstration of the existence of CCs strengthens the hypothesis of a phylogenetic link between gustatory and solitary chemosensory cells.

Distribution of vanilloid receptors in the rat laryngeal innervation.

OBJECTIVE: Capsaicin is known to selectively activate nociceptic sensory neurons through vanilloid receptors. In this study we investigated the distribution of vanilloid receptor subtype 1 (VR1) and vanilloid receptor-like protein 1 (VRL-1) in the rat larynx. MATERIAL AND METHODS: The distributions of VR1 and VRL-1 were determined immunohistochemically. The colocalization of vanilloid receptors with common choline acetyltransferase (cChAT), vasoactive intestinal polypeptide (VIP), substance P (SP) and neuronal nitric oxide synthase (nNOS) was also studied using an immunohistochemical double-labeling technique. RESULTS: VRL-1-positive fibers were detected in the laryngeal epithelium and lamina propria. VR1-positive nerve fibers were seen in the lamina propria but not in the mucosal epithelium. VR1- and VRL-1-positive cells were distributed in the intralaryngeal ganglia and colocalization of capsaicin receptors with VIP, nNOS and cChAT was seen. CONCLUSION: These findings suggest that these capsaicin receptors participate in the parasympathetic innervation as well as in nociception of the rat larynx.

Identification and characterization of a specific sensory epithelium in the rat larynx.

A specific laryngeal sensory epithelium (SLSE), which includes arrays of solitary chemoreceptor cells, is described in the supraglottic region of the rat. Two plates of SLSE were found, one on each side of the larynx. The first plate was located in the ventrolateral wall of the larynx, and the second was located in the interarytenoidal region. In SLSE, immunoblotting showed the presence of alpha-gustducin and phospholipase C beta2 (PLCbeta2), which are two markers of chemoreceptor cells. At immunocytochemistry, laryngeal immunoreactivity for alpha-gustducin was localized mainly in solitary chemosensory cells. Double-label immunocytochemistry using confocal microscopy demonstrated that alpha-gustducin-expressing cells in large part colocalize type III IP3 receptor (IP3R3), another key molecule in bitter taste perception. However, some IP3R3-expressing cells do not colocalize alpha-gustducin. At ultrastructural immunocytochemistry, these cells showed packed apical microvilli, clear cytoplasmic vesicles, and cytoneural junctions. SLSE was characterized by high permeability to a tracer due to poorly developed junctional contacts between superficial cells. Junctions were short in length and showed little contact with the terminal web. Ultrastructural analysis showed deep pits among the superficial cells. In SLSE, high density of intraepithelial nerve fibers was found. The lamina propria of the SLSE appeared thicker than that in other supraglottic regions. It was characterized by the presence of a well-developed subepithelial nerve plexus. The immunocytochemical and ultrastructural data suggested that SLSE is a chemoreceptor located in an optimal position for detecting substances entering the larynx from the pharynx or the trachea.

Capsaicin receptor expression in rat laryngeal innervation.

Capsaicin elicits a sensation of burning pain by selectively activating sensory neurons that convey information about noxious stimuli to the central nervous system. Vanilloid receptor subtype 1 (VRI) and the vanilloid receptor-like protein 1 (VRL-1) are activated, not only by capsaicin, but also by noxious heat and protons, and it has been suggested that they are polymodal nociceptors. We investigated the expression of VR1 and VRL-1 in the rat larynx and nodose ganglion using VR1 and VRL-1 immunohistochemical analysis with visualization by diaminobenzidine reaction. Fibers positive for VRL-1 were detected in the laryngeal epithelium and lamina propria. Cells positive for VRL-1 were distributed in the intralaryngeal ganglia. Half of the neurons in the nodose ganglion had VR-1 immunoreactivity, and almost 10% of the nodose ganglion neurons were positive for VRL-1. These findings suggest that these capsaicin receptors play an important role in the nociception of the laryngeal innervation.

The safety of flexible endoscopic evaluation of swallowing with sensory testing in an outpatient otolaryngology setting.

OBJECTIVE: To study the safety of flexible endoscopic evaluation of swallowing with sensory testing in a private otolaryngology office setting. STUDY DESIGN: Five parameters were prospectively evaluated. These included airway compromise, epistaxis, change in heart rate, level of discomfort, and patient's willingness to repeat the examination in the future. METHODS: All persons undergoing flexible endoscopic evaluation of swallowing with sensory testing between July 1, 1999, and June 30, 2001, were prospectively evaluated. A flexible fiberoptic endoscope with a specially designed air port channel was passed transnasally (without topical anesthesia or nasal constriction) into the more patent nostril. Nasopharyngeal and laryngeal anatomy were first evaluated. Laryngopharyngeal sensory and motor function were then assessed, followed by a comprehensive swallowing evaluation. Five test parameters were examined during each study. Descriptive statistics were calculated. RESULTS: Three hundred forty-nine consecutive examinations in 305 adult patients with dysphagia were performed during the study period. Mild epistaxis occurred in four patients (1.1%). There were no episodes of airway obstruction or laryngospasm. There was no statistically significant difference between the average pretest and post-test heart rates; no patients became symptomatically bradycardic or tachycardic. The discomfort ratings were as follows: 44 patients (12.6%) rated the overall discomfort of the test as none, 169 (48.4%) thought it was mild, 110 (31.5%) described moderate discomfort, and 26 (7.5%) said it was severe. Three hundred forty-two (98%) of the patients would repeat the test in the future; seven patients (2%) said that they would not. CONCLUSIONS: Flexible endoscopic evaluation of swallowing with sensory testing is a safe, well-tolerated procedure to objectively evaluate patients with dysphagia when performed by an experienced speech-language pathologist with an otolaryngologist in attendance in an outpatient office setting.

Efeitos de baixas pressões no balonete da máscara laríngea na mucosa faringolaríngea do cão / Effects of low laryngeal mask cuff pressure on the laryngopharyngeal mucosa of dogs

Justificativa e Objetivos - Lesões da mucosa faringolaríngea e compressões de vasos e de nervos têm sido relatadas e atribuídas às altas pressões no balonete da máscara laríngea (ML). O objetivo deste trabalho foi estudar em cães a mucosa faringolaríngea em contato com o balonete da ML sob baixas pressões e avaliar as condições ventilatórias durante a anestesia. Método - Em 8 cães sob anestesia com pentobarbital foi inserida ML de número 4, mantendo-se a pressão no balonete em 60 cmH2O. Os atributos: freqüência de pulso (FP), pressão arterial média (PAM), pressão inspiratória (PI), pressão expiatória final de CO2 (PetCO2) e saturação de pulso de O2 (SpO2) foram estudados em 0 (controle), 30, 60, 90 e 120 minutos após a inserção da ML. Após eutanásia, realizouðse biópsias nas áreas da contato da mucosa faringolaríngea com a ML para exame à microscopia óptica (MO) e eletrônica de varredura (MEV). Resultados - Os atributos estudados mantiveramðse sem alterações significativas durante o experimento, ocorrendo apenas pequeno aumento dos valores da PAM e da PetCO2 nos tempos finais do experimento. À MO, o epitélio da mucosa faringolaríngea apresentouðse sem alterações na grande maioria das áreas examinadas, mas em algmas áreas houve perquena infiltração inflamatória de polimorfonucleares neutrófilos e leve congestão na camada subepitelial, sem diferença significativa entre as áreas (p < 0,05). O estudo à MEV também mostrou epitélio da mucosa laringofaríngea sem alterações significativas. Conclusões - Em cães, a utilização de pressão de 60 cmH2O no balonete da ML assegura perfeita manutenção da permeabilidade das vias aéreas e não provoca alterações na mucosa faringolaríngea

Calbindin D28k-immunoreactive afferent nerve endings in the laryngeal mucosa.

The distribution of the calbindin D28k in the laryngeal sensory structures was studied by immunohistochemistry, immunoelectronmicroscopy, and double immunofluorescence with calretinin-immunoreactivity. Moreover, origin of the nerve endings were observed using retrograde tracer, fast blue. Immunoreactivity for calbindin D28k was found in the various types of nerve endings in the larynx, namely, laminar nerve endings, nerve endings associated with the taste buds, intraepithelial nerve endings, and endocrine cells. The laminar endings with calbindin D28k-immunoreactivity were observed in the subepithelial connective tissue. In some endings, terminals were expanded. The laminar endings were also observed in the perichondrium of the epiglottic cartilage. In the epiglottic and arytenoid epithelia, thick nerve fibers with calbindin D28k-immunoreactivity ascending to taste buds and intragemmal nerve fibers were also observed. Within the epithelial layer, intraepithelial free nerve endings with calbindin D28k-immunoreactivity were observed. Furthermore, diffuse endocrine cells were observed within the laryngeal epithelium. By immunoelectron microscopy, immunoreaction products in the endings mentioned above were localized in the cytoplasm of the axon terminals and nerve fibers which contained with numerous mitochondria. Out of the 100 laminar endings, 18 endings were immunopositive for both calbindin D28k and calretinin, 33 were positive for calbindin D28k but negative for calretinin, and 49 were positive for only calretinin in the double immunofluorescence microscopy. The nerve fibers associated with the taste buds and the free nerve endings, which immunostained for calbindin D28k, were not stained with antibody against calretinin. After injection of the fast blue in the laryngeal mucosa, fast blue-labeled cells were mainly observed in the nodose ganglia. Of the total number of labeled cell in the nodose and dorsal root ganglia at the level C1 to Th2, 65.1% occurred in nodose ganglia (572/879, n = 6). In the nodose ganglia, 79.7% of labeled cells (456/572) were immunoreacted for calbindin D28k. The distribution of calbindin D28k-immunoreactivity may be differnt from that of calretinin. It is suggested that calbindin D28k have regulatory role on intracellular calcium concentration in the laryngeal sensory corpuscles.

The safety of flexible endoscopic evaluation of swallowing with sensory testing (FEESST): an analysis of 500 consecutive evaluations.

We assessed the safety of a new office or bedside method of evaluating both the motor and sensory components of swallowing called flexible endoscopic evaluation of swallowing with sensory testing (FEESST). FEESST combines the established endoscopic evaluation of swallowing with a technique that determines laryngopharyngeal sensory discrimination thresholds by endoscopically delivering air-pulse stimuli to the mucosa innervated by the superior laryngeal nerve. Endoscopic assessment of laryngopharyngeal sensory capacity followed by endoscopic visualization of deglutition was prospectively performed 500 times in 253 patients with dysphagia over a 2.5-year period in a tertiary care center. The patients had a variety of underlying diagnoses, with stroke and chronic neurological disease predominating (n = 155). To determine the safety of FEESST, the presence of epistaxis, airway compromise, and significant changes in heart rate before and after the evaluation were assessed. Patients were also asked to rate the level of discomfort of the examination; 498 evaluations were completed. There were three instances of epistaxis that were self-limited. There were no cases of airway compromise. There were no significant differences in heart rate between pre- and posttest measurements (p > 0.05). Eighty-one percent of patients noted either no discomfort or mild discomfort as a result of the examination. In conclusion, FEESST is a safe method of evaluating dysphagia in the tertiary care setting and may also have application for the chronic care setting.

Changes in the distribution of the substance P and calcitonin gene-related peptide immunoreactive nerve fibers in the laryngeal mucosa of chronically hypoxic rats.

The distribution and abundance of substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactive nerve fibers in four different regions of the laryngeal mucosa were compared between normoxic and chronically hypoxic rats (10% O2 and 3.0-4.0% CO2 for 3 months). In the chronically hypoxic laryngeal mucosa, the number of SP and CGRP fibers within and just beneath the epithelium, and around the laryngeal gland was increased in comparison with those in the normoxic controls. Especially in the epiglottic and arytenoid regions, the number of intraepithelial SP fibers was increased remarkably. Most intraepithelial SP and CGRP fibers penetrated into the epithelium to extend to the luminal surface. There was no distinct difference in the distribution and abundance of these peptidergic fibers in the mucosa of the normoxic and chronically hypoxic vocal cord regions. These results suggest that the increased density of SP and CGRP fibers within the epithelium of the upper laryngeal mucosa is a predominant feature of hypoxic adaptation, and this may be involved in airway protection, swallowing, and other functions in the chronically hypoxic environment. In addition, the increased SP and CGRP fibers around the laryngeal gland suggest an enhanced mucous secretion, and this may participate in the airway defense mechanism in low O2 conditions.

Beaded nerve terminals in feline laryngeal mucosa.

To investigate the mechanism of airway defense reflex, beaded nerve terminals were studied by immunohistochemical techniques. In the supraglottic region the density of PGP 9.5-immunoreactive nerve fibers was the highest at the base of the glottic surface in the epiglottis, and in the glottic region it was the highest in the arytenoid region. In the subglottic region the number of positive nerve fibers was less than the number at the base of the glottic surface in the epiglottis, and when the laryngeal mucosa was processed with NaOH to dissolve the epithelium, it was possible to observe beaded nerve terminals more clearly. These beaded nerve terminals were found just beneath, in the epithelial basement membrane. Electron microscopic examination of beaded nerve terminals revealed a large quantity of secretory granules and mitochondria, suggesting that their structure is similar to that of nerve terminals. Thus these beaded nerve terminals may function as mechanoreceptors.

Calretinin-immunoreactive laminar nerve endings in the laryngeal mucosa of the rat.

The distribution of laminar nerve endings that contained immunoreactive calretinin was examined in the laryngeal mucosa of the adult rat. In whole-mount preparations, the immunoreactive laminar endings were distributed in the supraglottic region but not in the subglottic region. The laminar endings that arose from thick nerve fibers with or without swellings were identified as corpuscles with many variform terminal arborizations. They appeared to be located at the interface between the epithelium and the subepithelial connective tissue. The terminals were scattered under the basal lamina of the epithelium, and some of them were located within the epithelial layer. Immunoelectron microscopy revealed that both sub- and intraepithelial immunoreactive terminals that were filled with mitochondria were partly or totally ensheathed by Schwann cell processes. The denervation experiments, in which the superior laryngeal nerve was cut unilaterally or bilaterally, suggested that the laminar endings originate from the superior laryngeal nerve with strict ipsilateral innervation. The laminar endings might be associated with detection of changes in pressure in the laryngeal cavity or chemical stimuli.

Fiberoptic endoscopic evaluation of swallowing with sensory testing (FEESST) in healthy controls.

The purpose of this study was to introduce a new method of bedside assessment of both the motor and sensory components of swallowing called fiberoptic endoscopic evaluation of swallowing with sensory testing (FEESST). This approach combines the established bedside endoscopic swallowing evaluation with a more recently described technique that allows objective determination of laryngopharyngeal (LP) sensory discrimination thresholds by delivering air pulse stimuli to the mucosa innervated by the superior laryngeal nerve via a flexible endoscope. A prospective study was conducted of FEESST in 20 healthy control subjects, mean age of 34 +/- 11 years. LP sensory thresholds were defined as either normal (< 4.0 mmHg air pulse pressure [APP]), moderate deficit (4.0-6.0 mmHg APP), or severe deficits (> 6.0 mmHg APP). Subsequent to LP sensory testing, food of varying consistencies, mixed with green food coloring, was given and attention was paid to spillage, laryngeal penetration, pharyngeal residue, aspiration, and reflux. Therapeutic maneuvers such as postural changes and airway protection techniques were performed on each subject to determine if the assessed swallowing parameters were affected by maneuvers. All patients completed the study; all had normal LP sensory discrimination thresholds (2.9 +/- 0.7 mmHg APP). There were no instances of spillage, laryngeal penetration, or aspiration. Two of 20 subjects had pharyngeal residue and 2 of 20 had reflux. Institution of therapeutic maneuvers resulted in a predictable change in the endoscopic view of the laryngopharyngeal anatomy. FEESST provides comprehensive, objective sensory and motor information about deglutition in the bedside setting and might have implications for the bedside diagnosis and management of patients with dysphagia.

Distribution of NADPH-diaphorase activity in the feline laryngeal mucosa.

We studied nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity in the feline laryngeal mucosa using a histochemical technique in an effort to clarify the role of nitric oxide (NO) in the larynx. Many NADPH-diaphorase-positive nerve fibres were distributed around the blood vessels and the laryngeal glands. The majority of neuronal cells in the intralaryngeal ganglia were NADPH-diaphorase-positive. It is likely that NADPH-diaphorase-positive nerve fibres around the blood vessels and glands in the laryngeal mucosa originate from the intralaryngeal ganglia, and that NO regulates circulation and secretion in the larynx.

Ultrastructure of the myelinated nerve fibers in the feline laryngeal mucosa.

We studied the myelinated sensory nerve fibers in the feline laryngeal mucosa. Myelinated afferent nerve fibers (A-delta type) present in the lamina propria showed deterioration of the myelin sheath and Schwann cells under the basement membrane. Axons penetrated the basement membrane and entered the intercellular space of the epithelium. Nerve endings with many mitochondria and small clear vesicles existed in the intercellular space. No synapse-like structure was found between the endings and the surrounding epithelial cells. It is likely that these endings act as mechanosensitive receptors that respond to water or chemical stimuli and that participate in eliciting swallowing, coughing, and bronchoconstriction.