Novel pathway for LPS-induced afferent vagus nerve activation: possible role of nodose ganglion

The afferent vagus nerve has been suggested to be an important component for transmitting peripheral immune signals to the brain. However, there is inconsistent evidence showing that subdiaphragmatic vagotomy did not inhibit the brain mediated behavioral and neural effects induced by the peripheral application of lipopolysaccharide (LPS). LPS triggers innate immune cells through Toll-like receptor 4 (TLR4). In the present study, we found that TLR4 mRNA and protein was expressed in the rat nodose ganglion. Thus, it is suggested that LPS could activate afferent vagus nerve at the level of nodose ganglion, which exists centrally from the subdiaphragmatic level of vagus nerve. The results could provide evidence for the novel pathway of LPS-induced afferent vagus nerve activation.     

Vagal afferent innervation of the lower esophageal sphincter

To supply a fuller morphological characterization of the vagal afferents innervating the lower esophageal sphincter (LES), specifically to label vagal terminals in the tissues forming the LES in the gastroesophageal junction, the present experiment employed injections of dextran biotin into the nodose ganglia of rats. Four types of vagal afferents innervated the LES. Clasp and sling muscle fibers were directly and prominently innervated by intramuscular arrays (IMAs). Individual IMA terminals subtended about 16° of arc of the esophageal circumference, and, collectively, the terminal fields were distributed within the muscle ring to establish a 360° annulus of mechanoreceptors in the sphincter wall. 3D morphometry of the terminals established that, compared to sling muscle IMAs, clasp muscle IMAs had more extensive arbors and larger receptive fields. In addition, at the cardia, local myenteric ganglia between smooth muscle sheets and striated muscle bundles were innervated by intraganglionic laminar endings (IGLEs), in a pattern similar to the innervation of the myenteric plexus throughout the stomach and esophagus. Finally, as previously described, the principle bundle of sling muscle fibers that links LES sphincter tissue to the antropyloric region of the lesser curvature was innervated by exceptionally long IMAs as well as by unique web ending specializations at the distal attachment of the bundle. Overall, the specialized varieties of densely distributed vagal afferents innervating the LES underscore the conclusion that these sensory projections are critically involved in generating LES reflexes and may be promising targets for managing esophageal dysfunctions.     

Retrograde HRP demonstration of afferent projections to the midbrain and nest calls in the ring dove

Midbrain control of vocalization was evaluated in the ring dove by determining the major afferent inputs with retrograde tract tracing technique. Horseradish peroxidase was infused into various portions of the nucleus intercollicularis, an estrogen concentrating area, which disrupts nest calls when lesioned and induces the vocalization when stimulated by estrogen. Most labelled cell bodies were found in the archistriatum, including a region homologous to the mammalian amygdala.     

Immunohistochemical and biochemical analysis of serotonin and substance P colocalization in the nucleus tractus solitarii and associated afferent ganglia of the rat

In a previous study of afferent projections to the nucleus tractus solitarii (NTS), it was shown that over half of the retrogradely-labelled neurons in the nucleus raphe pallidus contained serotonin-immunoreactivity and over half of these neurons contained substance P-immunoreactivity, suggesting that these two putative neurotransmitters are colocalized in NTS-afferent neurons. The objectives of the present study were to 1) directly determine if varicosities in the NTS, the area postrema (AP), and the dorsal motor nucleus of the vagus nerve (DMN) do contain both transmitters, 2) determine if primary afferent neurons in the nodose and pretrosal ganglia might also colocalize serotonin and substance P, and 3) quantify the amount of substance P that is contained in serotonergic varicosities in the NTS. Distributions and colocalization of substance P and serotonin in the NTS were studied using dual-color immunohistochemistry, while the quantity of substance P in serotonergic varicosities was assessed by radioimmunoassay (RIA) using micropunches from the NTS of 5,7-dihydroxytryptamine-(5,7 DHT-) and vehicle-treated rats. Varicosities that contained both serotonin- and substance P-immunoreactivity were found in the NTS, the DMN, and the AP. Double-labelled varicosities were common in the NTS and DMN (i.e., qualitatively similar to the density seen in the hypoglossal nucleus and in the ventral horn of the cervical spinal cord); however, the vast majority of the varicosities in these autonomic areas only displayed immunoreactivity for one or the other of these transmitters. This paucity of doubly-labelled varicosities, in comparison to the number of singly-labelled varicosities, was reflected in the lack of a significant decrease in substance P levels as determined by RIA of micropunches taken from caudal and intermediate levels of the NTS in 5,7 DHT- and vehicle-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

The cells of origin of the hypoglossal afferent nerves and central projections in the cat

The cells of origin for the hypoglossal afferent nerves of the cat and their central projections were examined using the transganglionic and somatopetal transport of horseradish peroxidase (HRP). Primary afferent neurons from the hypoglossal nerve were located in the trigeminal ganglion, the superior ganglion of glossopharyngeal and vagal nerves, and the first 3 cervical ganglia. The central projections of hypoglossal afferents were organized in a selective manner according to their cells of origin. The primary afferent nerves originating from the trigeminal ganglion terminated in the subnucleus dorsalis (Vpd) of the principal nucleus (Vp), lateral margin of the caudal pars interpolaris (Vi), interstitial nucleus and laminae I and V of the pars caudalis (Vc). The projection of the afferent nerves for glossopharyngeal and vagal origins are similarly organized in the Vi and Vc to those of trigeminal origin, but differed in that they terminated ipsilaterally in the caudal half of the solitary nucleus and bilaterally in the commissural nucleus. The primary afferents arising from the first 3 cervical ganglia terminated in laminae I and V of the corresponding cervical cord segments.     

Central projections of coarse and fine vagal axons of the cat

We used the wallerian degeneration of vagal afferents and the retrograde transport of WGA-HRP microinjected in the nucleus of the tractus solitarius (NTS) to study the central projections of myelinated and unmyelinated vagal axons. We concluded that the set of largest nodose cells projected to the dorsolateral, interstitial, ventral, ventrolateral and intermediate NTS subnuclei, while the smaller nodose cells terminated in the medial, dorsal, gelatinosus and commissural NTS subnuclei.     

Connections of a vagal communicating branch in the ferret I. Pathways and cell body location

In contrast to most other species, ferrets possess a single communicating branch connecting the dorsal and ventral vagal trunks immediately rostral to the diaphragm. This branch is being used in physiological studies of gastrointestinal function and emesis. However, the fibre routes which pass through this branch are not known. In this study, the afferent and efferent pathways within this supradiaphragmatic vagal communicating branch of the ferret were studied through the use of the horseradish peroxidase (HRP) tracing technique. The region of the branch was exposed using a thoracotomy and HRP crystals were applied to one of the following: (A) the ventral end of the communicating branch, (B) the dorsal end of the communicating branch, (C) the distal end of the dorsal vagal trunk rostral to the communicating branch or (D) the distal end of the ventral vagal trunk rostral to the communicating branch. Following a 72 hour survival period, the animals were reanaesthetized and perfused. The superior cervical and nodose ganglia and the brain stem were processed using the tetramethylbenzidine method. Following application of HRP to the cut ventral end of the communicating branch, labelled cell bodies were found in the left and right nodose ganglia and in the left dorsal motor nucleus of the vagus. After HRP application to the cut dorsal end of the communicating branch, labelled cells were found in the left and right nodose ganglia. No HRP containing cell bodies were found following HRP application to the cut distal end of either the dorsal or the ventral vagal trunk. These results indicate that several afferent pathways exist within the branch, although only one consistently labelled efferent pathway was found.     

The renal afferent pathways in the rat: a pseudorabies virus study

Retrograde tract tracing studies have indicated that dorsal root ganglion cells from T₈ to L₂ innervate the rat's left kidney. Electrophysiology studies have indicated that putative second-order sympathetic afferents are found in the dorsal horn at spinal segments T₁₀ to L₁ in laminae V–VII. Here, the spread of pseudorabies virus through renal sensory pathways was examined following 2–5 days post-infection (PI) and the virus was located immunocytochemically using a rabbit polyclonal antibody. Two days PI, dorsal root ganglion neurons (first-order sympathetic afferents) were infected with PRV. An average of 1.2, 0.8, 2.1 and 4.4% of the infected dorsal root ganglion neurons were contralateral to the injected kidney at spinal segments T₁₀, T₁₁, T₁₂ and T₁₃, respectively. Four days PI, infected neurons were detected within laminae I and II of the dorsal horn of the caudal thoracic and upper lumbar spinal cord segments. The labeling patterns in the spinal cord are consistent with previous work indicating the location of renal sympathetic sensory pathways. The nodose ganglia were labeled starting 4 days PI, suggesting the involvement of parasympathetic sensory pathways. Five days PI, infected neurons were found in the nucleus tractus solitarius. In the present study, it was unclear whether the infected neurons in the nucleus tractus solitarius are part of sympathetic or parasympathetic afferent pathways or represent a convergence of sensory information. Renal denervation prevented the spread of the virus into the dorsal root ganglia and spinal cord. Sectioning the dorsal roots from T₁₀–L₃ blocked viral spread into the spinal cord dorsal horn, but did not prevent infection of neurons in dorsal root ganglion nor did it prevent infection of putative preganglionic neurons in the intermediolateral cell column. The present results indicated that renal afferent pathways can be identified after pseudorabies virus infection of the kidney. Our results suggest that renal afferents travel in sympathetic and parasympathetic nerves and that this information may converge at the NTS.     

Vagus nerve afferent and efferent innervation of the rat uterus: An electrophysiological and HRP study

To determine a possible brainstem connection with the uterus, a study with electrophysiological techniques and horseradish peroxidase (HRP) tracing was performed in the rat. Neurons of the nucleus of the tractus solitarius decreased in discharge frequency during cervicovaginal distension. HRP injections into the uterine walls resulted in the appearance of labelled cells in the nodose ganglion and in the dorsal motor nucleus of the vagus nerve. The results demonstrate a direct bidirectional vagal complex-uterus connection via the vagus nerve. Results are discussed in terms of a complex uterus control system in which the paraventricular nucleus might play an integrative role.     

Afferent innervation of the trachea during postnatal development

Retrograde axonal transport of horseradish peroxidase was used in this study to determine the location and basic morphological parameters of neurons innervating the trachea in newborn, 10-, 20-, 30-day-old and 2-month-old kittens. Labeled neurons were detected in all animals in the nodose ganglion of the vagus nerve and in the spinal ganglia (C1-C7 and T1-T6 after injection of tracer into the cervical trachea, C5-C7 and T1-T8 with injection into the thoracic part of the trachea) from both sides. The content of vagal and spinal afferent neurons innervating the cervical part of trachea declined during development. The number of spinal afferent neurons with connections to the thoracic trachea did not change but the quantity of cells in nodose ganglion supplying the thoracic trachea increased from the moment of birth till 10 and 20 days and decreased later in postnatal development. In newborn, 10-day-old and 20-day-old animals, the largest number of afferent cells was connected with the cervical part of the trachea in comparison with the thoracic one, whereas in 2-month-old kittens the relation was opposite. We suggest that afferent innervation of the trachea is not morphologically complete at the moment of birth and does not become mature until the second month of life.     

Trigeminal primary afferent projections to "non-trigeminal" areas of the rat central nervous system.

The central projections of rat trigeminal primary afferent neurons to various "non-trigeminal" areas of the central nervous system were examined by labeling the fibers with wheat germ agglutinin-horseradish peroxidase (WGA-HRP) transported anterogradely from the trigeminal ganglion. This technique produced a clear and comprehensive picture of trigeminal primary afferent connectivity that was in many ways superior to that which may be obtained by using degeneration, autoradiography, cobalt labeling, or HRP transganglionic transport techniques. Strong terminal labeling was observed in all four rostrocaudal subdivisions of the trigeminal brainstem nuclear complex, as well as in the dorsal horn of the cervical spinal cord bilaterally, numerous brainstem nuclei, and in the cerebellum. Labeling in the ipsilateral dorsal horn of the cervical spinal cord was very dense at C1, moderately dense at C2 and C3, and sparse at C4-C7. Numerous fibers crossed the midline in the medulla and upper cervical spinal cord and terminated in the contralateral pars caudalis and dorsal horn of the spinal cord from C1-C5. The latter axons terminated most heavily in the mandibular and ophthalmic regions of the contralateral side. Extremely dense terminal labeling was observed in the ipsilateral paratrigeminal nucleus and the nucleus of the solitary tract, moderate labeling was seen in the supratrigeminal nucleus and in the dorsal reticular formation, and small numbers of fibers were observed in the cuneate, trigeminal motor, lateral and superior vestibular nuclei, and in the cerebellum. The latter fibers entered the cerebellum in the superior cerebellar peduncle and projected to the posterior and anterior lobes as well as to the interposed and lateral deep cerebellar nuclei. Most projections in this study originated from fibers in the dorsal part of the spinal tract of V, suggesting a predominantly mandibular origin for these fibers. Projections from the ophthalmic and maxillary divisions, in contrast, were directed mainly to the cervical spinal cord bilaterally, to contralateral pars caudalis, and to certain areas of the reticular formation. In conclusion, this study has demonstrated that somatosensory information from the head and face may be transmitted directly to widespread and functionally heterogeneous areas of the rat central nervous system, including the spinal cord dorsal horn, numerous brainstem nuclei, and the cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)     

Involvement of nitric oxide in re-innervation of rat molar tooth pulp following transection of the inferior alveolar nerve

The aim of this study was to elucidate whether nitric oxide (NO) is involved in re-innervation of rat molar tooth pulp following transection of the inferior alveolar nerve. The inferior alveolar nerves (IAN) of rats were transected unilaterally under anesthesia with chloral hydrate. The animals received horseradish peroxidase (HRP) application to mandibular molar tooth pulps on both sides and were fixed by transvascular perfusion. The average number of labeled cells on each side of the trigeminal ganglion was not significantly different [101±11 (mean±S.E.M.; n=6, left) and 89±11 (n=6, right)]. With HRP application on postoperative day 3, the ratio of the number of labeled neurons in the transected vs. non-transected (contralateral) sides was 31.5±5.8% (n=11). The i.p. administration of N^ω-nitro-

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-arginine methyl ester (

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-NAME; 100 mg/kg, once a day for a period of 4 days), but not

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-NAME, significantly decreased the ratio of the number of labeled neurons (10.1±7.0%, n=10).

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-Arginine (300 mg/kg, i.p., once a day for a period of 4 days) slightly increased the number of labeled neurons on the transected side. Clonidine (25 μg/kg, i.p., once a day for a period of 4 days) failed to exhibit any significant effect on nerve regeneration. In the trigeminal ganglion ipsilateral to the transected IAN on postoperative day 4, NADPH-diaphorase (NADPH-d)-positive neurons had significantly increased. On the other hand, no changes in NADPH-d were observed in the superficial layers of the subnucleus caudalis of the spinal trigeminal nucleus from where primary neurons innervating the mammalian tooth pulp project. These results suggest that NO is involved in several mechanisms related to neuronal regeneration.     

Autoradiographic study on the distribution of vagal afferent nerve fibers in the gastroduodenal wall of the rabbit

Following unilateral supranodose vagotomy which eliminated vagal efferent fibers, [3H]leucine was injected into the ipsilateral no-dose ganglion of the rabbit, which was allowed to survive for 10 days. Autoradiographic examination of the distribution of vagal afferent fibers in the gastroduodenal wall revealed many nerve bundles of labeled afferent fibers present in the subserous plexus between the serosa and the muscle coat, where they branched and descended into the muscle coat. Some of the fibers appeared to interact with some myenteric neurons and muscle fibers in a manner suggesting that the afferent fibers may make synaptic contact with the enteric neurons and innervate or attach to the muscle fibers. Furthermore, the afferent fibers were observed in the submucosal plexus between the muscle coat and the muscularis mucosae. In the mucosa the afferent nerve branched in filaments containing one or several afferent fibers extending from the muscularis mucosae through the mucous lamina propria and to the mucous membrane composed of epithelial cells. It was speculated that the afferent fibers terminated as free endings near the mucous membrane.     

Autoradiographic demonstration of the distribution of vagal afferent nerve fibers in the epiglottis of the rabbit

After injection of [3H]leucine into the nodose ganglion of a rabbit autoradiographic examination of the distribution of vagal afferent fibers in the epiglottal wall revealed many nerve bundles of labeled afferent fibers present in the submucosal plexus between the cartilage tissue and the mucosa. The labeled afferent fibers, most of which were myelinated (while a few were unmyelinated), descended towards the mucosa, and then appeared to demyelinate at the subepithelial layer of the mucosa. The labeled afferent fibers entered the mucosal epithelium, terminated as free endings in the intercellular space among the epithelial cells, and extended near the mucosal surface. Grains were also observed near the taste buds in the epithelium, which suggests that some vagal afferent fibers innervated the epiglottal taste buds.     

Brainstem distribution of neurons with efferent projections in the cervical vagus of the dog

The distribution within the brainstem of cell bodies and efferent fibers projecting in the cervical vagus was studied with retrograde transport of horseradish peroxidase (HRP). Five to eight days after multiple microinjections of HRP into either the cervical vagosympathetic trunk or the nodose ganglion the brainstems and nodose ganglia were perfused and processed by the tetramethyl benzidine method. HRP-positive neurons were found in three brainstem regions: a dorsal cell column comprising the dorsal motor nucleus of the vagus (dmnX), a ventrolateral group in the region of nucleus ambiguus (nA), and scattered cells along a line between these columns. The density of labeled neurons was greatest within dmnX. Axons from cells of the ventrolateral column projected dorsomedially; just ventral to dmnX they turned laterally to exit the medulla in multiple rootlets. Within nA labelled neurons were distributed according to size, with larger cells more medial and smaller ones more lateral. Caudal to nA in nucleus retroambigualis and nucleus dorsalis medialis cell bodies appeared segregated into clusters.     

The central distribution of the cervical vagus nerve and gastric afferent and efferent projections in the rat

The medullary distribution of afferent fibers and cells of origin of the cervical vagal trunk and of the vagal innervation of the stomach have been studied using the anterograde and retrograde transport of horseradish peroxidase (HRP). Injections of HRP were made into the cervical vagus nerve, the stomach wall, the proximal small intestine, or the peritoneal cavity. Two to four days following the injections, the rats were perfused and the medullae oblongatae and nodose ganglia were processed using the tetramethyl benzidine method. Cervical vagus nerve injections of HRP resulted in heavy anterograde labeling in the ipsilateral nucleus of the tractus solitarius (NTS) and the commissural nucleus. Lighter labeling was seen in these regions on the contralateral side, but did not extend as far rostrally in the NTS. Labeling was also seen in the area postrema. Retrogade labeling of somata was present in the ipsilateral side in the nodose ganglion, throughout the whole extent of the dorsal motor nucleus of the vagus, much of the nucleus ambiguus and in rostral levels of the cervical spinal cord. After stomach injections, labeling indicative of afferent fibers was observed bilaterally in the dorsomedial and medial portions of the NTS and in the commissural nucleus. Labeled efferent fibres arose from neurons in the dorsal motor nucleus of the vagus, nucleus ambiguus and the cervical spinal cord. Retrogradely labeled somata were found bilaterally, throughout the rostrocaudal length of the dorsal motor nucleus in all cases with stomach injections. In some, but not all cases, labeled somata were seen bilaterally in compact areas within the nucleus ambiguus, particularly rostrally. Control injections of HRP into the intestinal wall and peritoneal cavity indicated that the stomach was the primary source of afferent and efferent labeling in the medulla following subdiaphragmatic injections.     

The effects of lithium chloride on the activity of the afferent nerve fibers from the abdominal visceral organs in the rat

The effect of lithium chloride on the activity of the afferent nerve fibers from the abdominal organs was studied in anesthetized rats. The administration of the lithium chloride solution (0.15 M) over the mesentery increased afferent discharge rate of the splanchnic and vagal gastric nerve. Injection of the same solution into the portal vein caused an increase in afferent activity of the vagal hepatic nerve. Further, infusion of the same solution into the duodenum resulted in facilitation of the afferent activity of the splanchnic as well as vagal celiac nerves. The results may explain the mechanism played by lithium chloride as unconditioned stimulus in the conditioned taste aversion paradigm.     

The distribution of the cat''s carotid sinus nerve afferent and efferent cell bodies using the horseradish peroxidase technique

The location of both afferent and efferent carotid sinus nerve (CSN) cell bodies in the cat has been determined using the horseradish peroxidase (HRP) technique. Following a limited exposure of the central cut end of the CSN to HRP, labeled sensory ganglion cells were found in both the petrosal and superior ganglia of the IXth cranial nerve. An average of 387 in the former and 16 cells in the latter ganglion were labeled.

Retrogradely labeled neurons were found only within the ipsilateral medulla. These cells were both round and spindle shaped and had an average somal diameter of 19 μm. The number of these CSN efferent cell bodies ranged from 1 to a maximum of 20 in a given animal. They were found in both the nucleus parvocellularis and the retrofacial nucleus. In 8 cases axonal labeling was observed. Axons generally projected dorsomedially from the ventrolateral medulla.     

The postganglionic parasympathetic fibers originating in the otic ganglion are distributed in several branches of the trigeminal mandibular nerve: an HRP study in the guinea pig

Application of HRP to the proximal stumps of the ramifications of the trigeminal nerve shows that all those belonging to the mandibular branch contain parasympathetic fibers originating in the otic ganglion. The nerve with the largest proportion of these fibers is the auriculotemporal nerve (50–60% of all labeled neurons), while the smallest percentages are found in the lingual nerve and motor root (about 5% each). The presence of otic fibers in the inferior alveolar, mylohyoid, buccal and motor branches of the trigeminal nerve has not hitherto been reported.