The central projections of the laryngeal nerves in the rat (original) (raw)
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Innervation of the larynx, pharynx, and upper esophageal sphincter of the rat
Journal of Comparative Neurology, 1994
We identified a ‘semicircular’ compartment of the rat thyropharyngeus muscle at the pharyngoesophageal junction and used the glycogen depletion method to determine how the fibers of this muscle (as well as all others of the pharynx and larynx) are innervated by different cranial nerve branches. The semicircular compartment appears anatomically homologous to the human cricopharyngeus muscle, an important component of the upper esophageal sphincter. While we found very little overlap in the muscle targets of the pharyngeal, superior laryngeal and recurrent laryngeal nerves within the pharynx and larynx, the semicircular muscle receives a dual, interdigitating innervation from two vagal branches: the pharyngeal nerve and a branch of the superior laryngeal nerve we call the dorsal accessory branch. After applying horseradish peroxidase to either of these two nerves, we compared the distribution and number of cells labeled in the brainstem. The dorsal accessory branch conveys a more heterogeneous set of efferent fibers than does the pharyngeal nerve, including the axons of pharyngeal and esophageal motor neurons and parasympathetic preganglionic neurons. The observed distribution of labeled motor neurons in nucleus ambiguus also leads us to suggest that the semicircular compartment is innervated by two subsets of motor neurons, one of which is displaced ventrolateral to the main pharyngeal motor column. This arrangement raises the possibility of functional differences among semicircular compartment motor neurons correlated with the observed differences in brainstem location of cell bodies. © 1994 Wiley-Liss, Inc.
The location and axonal projections of laryngeal motoneurons (LMn) have been studied in rats and cats using horseradish peroxidase as a retrograde tracer. LMn are located in the caudal part of the ambiguus nucleus in both species. In the cat, LMn are organized in two groups with a specific orientation of their dendritic trees. LMn axonal projections are ipsilateral in cats and bilateral in rats. In the early literature there was some controversy about the uni-or bilateral origin of ambiguus nucleus (AN) fibers projecting to the laryngeal muscles in mammals [2]. Recently it has been reported that following transection and horseradish peroxidase (HRP) impregnation of left vagus nerve in both rats and monkeys, bilateral labeling of neurons appeared in the AN in rats, but only ipsilateral AN neurons showed HRP reaction products in monkeys [7]. On electrophysiological grounds, it has also been reported that the electrical stimulation of the contralateral recurrent laryngeal nerve (RLn) in cats fails to induce any antidromic field potential in the AN [l], Another not well-known aspect is the precise distribution of laryngeal motoneurons (LMn), although in previous reports it has been suggested that they are located in the posterior part of the AN [10] except a small group situated in the retrofacial nucleus [5]. The present study was undertaken to reexamine in detail the morphological organization of LMn in both cats and rats, using HRP as a retrograde tracer. Experiments were carried out on 5 cats and l0 rats anesthetized with ketamine (35 mg/kg, i.m.) and 12.5s/o urethane solution (6 mllkg), respectively. In both cats and rats a tracheotomy was made in order to freely manipulate the larynx. A total amount of 15 ¡rl (cats) and 5 ¡rl (rats) of a 5090 HRP solution (Sigma type VI) was injected bilaterally into the laryngeal muscles by means of a Hamilton microsyringe.
Intraepithelial Nerve Fibers Project Into the Lumen of the Larynx
The Laryngoscope, 2004
Objectives/Hypothesis: Studies on the morphology and location of the sensory receptors in the laryngeal mucosa have resulted in insufficient and sometimes conflicting data. In the present study the authors analyzed the distribution and morphology of sensory nerve plexuses and terminal fibers in the laryngeal mucosa of the rat. Study Design: Two groups of Male Wistar rats were used in this laboratory study; the larynx of the first group were used to analyse the sensitive innervation of its epithelium, whereas the larynx of the second group (controls) were tested for the specificity of the antibodies used. Methods: The larynges of the animals were entirely removed after perfusion, and coronal or horizontal sections were immunoprocessed for further randomized analysis of the mucosa. Primary afferents were detected by immunoreaction to two widely recognized markers of sensory nerves, calcitonin generelated peptide and substance P, and visualized using diaminobenzidine as a chromogen. Results: The nerve plexuses were more densely distributed in the dorsal half of the vocal folds and in the laryngeal aspect of the epiglottis. Dense networks of fine fibers with many varicosities en passant, immunoreactive for both calcitonin gene-related peptide and substance P, occurred in the lamina propria and along the epithelial thickness. Calcitonin gene-related peptideimmunoreactive and substance P-immunoreactive fibers extended across the epithelium and projected to the laryngeal lumen itself, reaching the space between the cilia. Conclusion: The projection of intraepithelial nerve fibers into the lumen of the larynx indicates that in the absence of mucus, nerve endings may be exposed and thus receive direct stimulation from airborne substances. Furthermore, it suggests that the laryngeal mucosa of the rat may constitute an experimental model for studying the direct activation or manipulation of primary afferents at the periphery and neurogenic inflammation.
The Human Laryngeal Innervation Revisited. The Role of the Neural Connections
Anatomical record (Hoboken, N.J. : 2007), 2018
In spite that vascular inconvenients or immunological rejections have been solved in relation with larynx transplant, a successful functional reinnervation has not been achieved. Some studies have suggested that laryngeal nerve connection may contain motor fibers, which could explain unexpected evoked responses in electromyographic studies or the different positions adopted of the vocal folds after similar nerve lesions. Ten patients with unexpected evoked responses after laryngeal nerve stimulation were selected. All the patients underwent a total laryngectomy due to oncological causes. In every case, laryngeal nerve connections were observed. All of them were morphologic and histologic processed for choline-acetyltransferase immunohistochemistry. The presence of motor axons in the nerve connections has been demonstrated, which would explain that the motor innervation to the laryngeal muscles could be dual through these variable connections. This also would justify the difficulty o...
The Anatomical Record, 2014
Changes in motoneurons innervating laryngeal muscles after section and regeneration of the recurrent laryngeal nerve (RLN) are far from being understood. Here, we report the somatotopic changes within the nucleus ambiguus (Amb) after the nerve injury and relates it to the resulting laryngeal fold impairment. The left RLN of each animal was transected and the stumps were glued together using surgical fibrin glue. After several survival periods (1, 2, 4, 8, 12, 16 weeks; at least six rats at each time point) the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles were injected with fluorescent-conjugated cholera toxin and the motility of the vocal folds evaluated. After section and subsequent repair of the RLN, no movement of the vocal folds could be detected at any of the survival times studied and the somatotopy and the number of labeled motoneurons changed. From 4 wpi award, the somatotopy was significantly disorganized, with the PCA motoneurons being located rostrally relative to their normal location. A rostrocaudal overlap between the two pools of motoneurons supplying the PCA and TA muscles was observed from 2 wpi onwards. Hardly any labeled neurons were found in the contralateral Amb in any of the experimental groups. An injury of the RLN leads to a reinnervation of the denervated motor endplates of PCA and TA. However, misdirected axons sprout and regrowth from the proximal stump to the larynx. As a result, misplaced innervation of muscles results in a lack of functional recovery of the laryngeal folds movement following a RLN injury. Anat Rec, 00:000-000, Abbreviations used: Amb 5 nucleus ambiguus; CT 5 cricothyroid muscle; CtB 5 cholera toxin subunit B; LCA 5 lateral cricoarytenoid muscle; PCA 5 posterior crocoarytenoid muscle; RLN 5 recurrent laryngeal nerve; SLN 5 superior laryngeal nerve; TA 5 thyroarytenoid muscle.
Projections of the internal branch of the superior laryngeal nerve in the cat.
LUCIER, G E., R. EGIZII AND J. 0. DOSTROVSKY Projections ofthe rnfernal branch ofthe superior laryngeal nerve ofrhr car. BRAIN RES BULL M(5) [713][714][715][716][717][718][719][720][721] 1986.-The internal branch of the supenor laryngeal nerve (tSLN) conveys sensory afferent mformatton from receptors located m the laryngeal mucosa. The objecttves of thts study were. to determine the specific anatomical locatton of iSLN cell bodies within the nodose ganglion, to ascertam whether the jugular ganglion mtght also contain ISLN atferent bodies; to determine whether the iSLN contains sympathetic efferents onginatmg m the cervical sympathettc ganglion; to determme whether the cell bodies of these efferents, if present, are localized wtthm a specdic region of thts ganglion and to trace the transganghonic projectton of ISLN afferents mto the bram stem. Horseradish peroxidase was applied to the iSLN m ten adult cats. Following a survival period of 72 hours, the animals were sacnficed and the tissue was processed according to the tetramethylbenztdme method. Reaction product was locahzed in the rostra1 end of the nodose ganglion extending into the exiting vagus nerve, m the caudal end of theJugular ganglion and m the postenor portion of the cervrcal sympathettc ganglion. Tr~sganglionic projections to the nucteus tractus sobtanus were localized prtmardy rn the dorsolateral subnucleus with substantial amounts of reaction product also in the intermediate and Interstitial subnuclei. Except for a small bilateral projection observed m the commissural subnucleus, no other proJecttons were seen to any other bram stem structures Internal superior laryngeal nerve Nucleus of the solitary tract
Firing properties of identified superior laryngeal neurons in the nucleus ambiguus in the rat
Neuroscience Letters, 2001
Superior laryngeal motoneurons control muscles in the larynx and recent work has shown they also have axon collaterals that project to cardiac vagal neurons in the nucleus ambiguus. The present study was undertaken to identify and examine the ®ring properties of superior laryngeal neurons (SLNs) in the rat. SLNs typically ®red spontaneously and repetitively at a rate of 4±7 Hz. The ®ring was continuous and showed little bursting activity. Firing evoked afterhyperpolarizations were insensitive to apamin but blocked by charybdotoxin. The voltage-gated currents in SLNs consist of a TTX-sensitive Na current and a 4-aminopyridine sensitive K current. It is likely that the activity of these neurons not only control respiratory laryngeal muscles, but may also provide an interaction between the respiratory system and the control of the heart rate. q
Intra-axonal recordings were made from 24 afferent fibres of the superior laryngeal nerve in and around the nucleus tractus solitarius, in 26 pentobarbitone-anaesthetized cats. Conduction velocity ranged from 15 to 38 m/s. Four afferents were injected with horseradish peroxidase. They showed dense terminal arborization in the region of the ventral and ventrolateral subnuclei of the nucleus tractus solitarius, both rostral and caudal to the obex. Six other intra-axonal recordings were thought to originate from axons of neurons postsynaptic to superior laryngeal afferents; one of these was injected with horseradish peroxidase and showed a similar arborization pattern to that of the afferent axons. In the same region, intracellular recordings were made from 124 neurons which responded to superior laryngeal nerve stimulation with excitatory postsynaptic potentials (mean latency 2.7 +/- 1.0 ms). Ninety-nine of these neurons were thought to receive a monosynaptic input. The stimulation threshold evoking these responses was similar to that which inhibited phrenic nerve discharge. Eleven of the monosynaptically excited neurons were injected with horseradish peroxidase. They had fusiform or stellate somata and simple dendritic trees, radiating mainly in the transverse plane. In one experiment, in which both a superior laryngeal nerve afferent fibre and a neuron were labelled, afferent terminal varicosities were found in close apposition with the postsynaptic membrane of the injected neuron. Four of 14 (29%) tested neurons could be antidromically activated from the C3 spinal segment. The stimulus thresholds and onset latencies of the responses of superior laryngeal nerve afferents and medullary neurons to stimulation of the superior laryngeal nerve are consistent with their involvement in the reflex inhibition of respiratory neurons evoked by superior laryngeal nerve stimulation.
Projections of the Internal Branch of the Superior Laryngeal Nerve of the Cat
LUCIER, G E., R. EGIZII AND J. 0. DOSTROVSKY Projections ofthe rnfernal branch ofthe superior laryngeal nerve ofrhr car. BRAIN RES BULL M(5) [713][714][715][716][717][718][719][720][721] 1986.-The internal branch of the supenor laryngeal nerve (tSLN) conveys sensory afferent mformatton from receptors located m the laryngeal mucosa. The objecttves of thts study were. to determine the specific anatomical locatton of iSLN cell bodies within the nodose ganglion, to ascertam whether the jugular ganglion mtght also contain ISLN atferent bodies; to determine whether the iSLN contains sympathetic efferents onginatmg m the cervical sympathettc ganglion; to determme whether the cell bodies of these efferents, if present, are localized wtthm a specdic region of thts ganglion and to trace the transganghonic projectton of ISLN afferents mto the bram stem. Horseradish peroxidase was applied to the iSLN m ten adult cats. Following a survival period of 72 hours, the animals were sacnficed and the tissue was processed according to the tetramethylbenztdme method. Reaction product was locahzed in the rostra1 end of the nodose ganglion extending into the exiting vagus nerve, m the caudal end of theJugular ganglion and m the postenor portion of the cervrcal sympathettc ganglion. Tr~sganglionic projections to the nucteus tractus sobtanus were localized prtmardy rn the dorsolateral subnucleus with substantial amounts of reaction product also in the intermediate and Interstitial subnuclei. Except for a small bilateral projection observed m the commissural subnucleus, no other proJecttons were seen to any other bram stem structures Internal superior laryngeal nerve Nucleus of the solitary tract
Immunohistochemical characterization of nerve elements in porcine intrinsic laryngeal ganglia
Polish Journal of Veterinary Sciences, 2023
The present study investigated the chemical coding of neurons and nerve fibres in local laryngeal ganglia in pigs (n=5) using double-labelling immunohistochemistry. Virtually all the neurons were cholinergic in nature (ChAT-or VAChT-positive). Only very solitary, small nerve cells (presumably representing interneurons) stained intensely for adrenergic marker, DβH. Many neurons also contained immunoreactivity for NOS (91%), VIP (62.7%), NPY (24.7%), galanin (10%), SP (1.3%) and CGRP (5.3%). No neurons expressing somatostatin or Leu-enkephalin were observed. Nearly all the neuronal somata were densely supplied with varicose cholinergic nerve terminals, which presumably represented preganglionic axons, and some of them were also closely apposed with CGRP-and/or SP-positive varicose nerve endings, which were putative collaterals of extrinsic primary sensory fibres. In conclusion, this study has revealed that intrinsic neurons in the porcine larynx, like in many other mammalian species studied, should be classified as parasympathetic cholinergic neurons expressing biologically active substances, predominantly NOS and VIP. Furthermore, they are likely to receive inputs from not only preganglionic neurons but also primary sensory nerve cells. Finally, it appears that the information on the occurrence of the local laryngeal ganglia should be regularly included in textbooks dealing with the cranial portion of the parasympathetic nervous system in mammals.