Distribution of CGRP-, somatostatin-, galanin-, VIP-, and substance P-immunoreactive nerve fibers in the chicken carotid body

Summary An immunoperoxidase method was used to investigate and compare the distribution of neuropeptide-immunoreactive (ir) nerve fibers and neurofilament-ir fibers in chick carotid body. The vagus nerve and its branches were intensely immunoreactive with an antiserum against chick neurofilaments. The branches from the vagus and the recurrent laryngeal nerves anastomosed within the connective tissue encircling the carotid body, and then entered the organ to form a network of neurofilament-ir fibers. Immunoreactivities for CGRP, somatostatin, galanin, VIP and substance P were found in the carotid body; they were located within varicose fibers. Immunoreactivity for each peptide was discretely and characteristically distributed. Dense networks of varicose CGRP-ir nerve fibers were found throughout the carotid body in close proximity to clusters of carotid body cells and to blood vessels. Substance P-ir fibers were distributed similarly to CGRP-ir fibers. Somatostatin-ir fibers appeared as patches distributed around chief cells. Numerous galanin- and VIP-ir nerve fibers were observed in the connective tissue surrounding the carotid body, but they occurred in only moderate densities in the parenchyma.     

Innervation of the C cells of chicken ultimobranchial glands studied by immunohistochemistry, fluorescence microscopy, and electron microscopy

Innervation of the ultimobranchial glands in the chicken was investigated by immunohistochemistry, fluorescence microscopy and electron microscopy. The nerve fibers distributed in ultimobranchial glands were clearly visualized by immunoperoxidase staining with antiserum to neurofilament triplet proteins (200K-, 150K- and 68K-dalton) extracted from chicken peripheral nerves. The ultimobranchial glands received numerous nerve fibers originating from both the recurrent laryngeal nerves and direct vagal branches. The left and right sides of the ultimobranchial region were asymmetrical. The left ultimobranchial gland had intimate contact with the vagus nerve trunk, especially with the distal vagal ganglion, but was somewhat separated from the recurrent nerve. The right gland touched the recurrent nerve, the medial edge being frequently penetrated by the nerve, but the gland was separated from the vagal trunk. The left gland was innervated mainly by the branches from the distal vagal ganglion, whereas the right gland received mostly the branches from the recurrent nerve. The carotid body was located cranially near to the ultimobranchial gland. Large nerve bundles in the ultimobranchial gland ran toward and entered into the carotid body. By fluorescence microscopy, nerve fibers in ultimobranchial glands were observed associated with blood vessels. Only a few fluorescent nerve fibers were present in close proximity to C cell groups; the C cells of ultimobranchial glands may receive very few adrenergic sympathetic fibers. By electron microscopy, numerous axons ensheathed with Schwann cell cytoplasm were in close contact with the surfaces of C cells. In addition, naked axons regarded as axon terminals or "en passant" synapses came into direct contact with C cells. The morphology of these axon terminals and synaptic endings suggest that ultimobranchial C cells of chickens are supplied mainly with cholinergic efferent type fibers. In the region where large nerve bundles and complex ramifications of nerve fibers were present, Schwann cell perikarya investing the axons were closely juxtaposed with C cells; long cytoplasmic processes of Schwann cells encompassed large portions of the cell surface. All of these features suggest that C-cell activity, i.e., secretion of hormones and catecholamines, may be regulated by nerve stimuli.     

Ontogeny of the carotid body and glomus cells distributed in the wall of the common carotid artery and its branches in the chicken

Summary Developmental patterns of immunoreactivity for serotonin and neuropeptide Y were investigated immunohistochemically in the carotid body and glomus cells in the wall of the common carotid artery and around its branches of chickens at various developmental ages. The development of peptidergic nerve fibers was also studied. Serotonin immunoreactivity began to appear in the glomus cells of the carotid body and around arteries at 10 days of incubation and became very intense from 12 days onwards. Neuropeptide Y immunoreactivity also appeared in these cells at 10 days, became intense at 14 days, and was sustained until 20 days. After hatching, neuropeptide Y immunoreactivity in the carotid body rapidly decreased with age and almost cisappeared at posnatal day 10. However, it persisted for life in the glomus cells distributed in the wall of the common carotid artery. Substance P- and calcitonin gene-related peptide (CGRP)-immunoreactive fibers first penetrated into the carotid body parenchyma at 12 days of incubation. These peptidergic nerve fibers in the carotid body and glomus cell groups in and around arteries gradually increased with age, and approached the adult state at 18 days of incubation. Only a few galanin-and vasoactive intestinal peptide (VIP)-immunoreactive fibers were observed in the late embryonic carotid bodies. They rapidly developed after hatching and reached adult numbers at postnatal day 10. During late embryonic and neonatal development, considerable numbers of met-enkephalin-immunoreactive fibers were detected in the connective tissue encircling the carotid body.     

Neuropeptide Y and vasoactive intestinal peptide coexist in rat thyroid nerve fibers emanating from the thyroid ganglion

Neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) occur in nerve fibers around blood vessels and between follicles in the thyroid gland of the mouse and rat. VIP-immunoreactive fibers are numerous, while NPY-immunoreactive fibers are fewer. Most of the latter fibers contain noradrenaline (NA) as well as NPY, while a subpopulation was found to contain VIP instead of NA. We have determined the origins of rat thyroid nerve fibers containing NPY, VIP or NPY/VIP by investigating 3 conceivable sources, i.e. the superior cervical ganglion, the nodose ganglion and the thyroid ganglion. Chemical sympathectomy or removal of the superior cervical ganglion did not affect the frequency of VIP-immunoreactive fibers but eliminated most of the NPY-immunoreactive fibers as well as all NA-containing nerve fibers (recognized by antibodies to dopamine-beta-hydroxylase). The NPY-immunoreactive fibers that remained after sympathectomy occurred around blood vessels and between follicles and contained VIP. Cervical vagotomy (removal of the nodose ganglion including the adjacent vagus) did not overtly affect the frequency of NPY/VIP-, VIP-, or NPY/NA-containing fibers in the thyroid. In contrast, extirpation of the thyroid ganglion, which is situated immediately outside the thyroid capsule, greatly reduced the number of VIP- and NPY/VIP-containing fibers in the rat thyroid. On the whole, the results of radioimmunoassay of NPY and VIP agreed well with the immunocytochemical findings. High performance liquid chromatography confirmed the identity of NPY and VIP. The present findings suggest the existence in the rat thyroid of one NPY-containing nerve fiber population that harbours NA and emanates from the superior cervical ganglion; one NPY-containing fiber population that is non-adrenergic, harbours VIP and originates in the thyroid ganglion; and a second VIP-containing fiber population that is devoid of NPY and appears to derive from the thyroid ganglion.     

FRS2 alpha 2F/2F mice lack carotid body and exhibit abnormalities of the superior cervical sympathetic ganglion and carotid sinus nerve

The docking protein FRS2α is an important mediator of fibroblast growth factor (FGF)-induced signal transduction, and functions by linking FGF receptors (FGFRs) to a variety of intracellular signaling pathways. We show that the carotid body is absent in FRS2α^2F/2F mice, in which the Shp2-binding sites of FRS2α are disrupted. We also show that the carotid body rudiment is not formed in the wall of the third arch artery in mutant embryos. In wild-type mice, the superior cervical ganglion of the sympathetic trunk connects to the carotid body in the carotid bifurcation region, and extends thick nerve bundles into the carotid body. In FRS2α^2F/2F mice, the superior cervical ganglion was present in the lower cervical region as an elongated feature, but failed to undergo cranio-ventral migration. In addition, few neuronal processes extended from the ganglion into the carotid bifurcation region. The number of carotid sinus nerve fibers that reached the carotid bifurcation region was markedly decreased, and baroreceptor fibers belonging to the glossopharyngeal nerve were absent from the basal part of the internal carotid artery in FRS2α^2F/2F mutant mice. In some of the mutant mice (5 out of 14), baroreceptors and some glomus cells were distributed in the wall of the common carotid artery, onto which the sympathetic ganglion abutted. We propose that the sympathetic ganglion provides glomus cell precursors into the third arch artery derivative in the presence of sensory fibers of the glossopharyngeal nerve.     

Sympathetic innervation of the carotid bifurcation in the rabbit and cat: Blood vessels,carotid body and carotid sinus

Summary Two postganglionic branches of the superior cervical ganglion enter the area of the carotid bifurcation in the rabbit and the cat. The common and external carotid arteries receive a rich adrenergic nerve supply, which can be demonstrated by fluorophores of biogenic amines appearing after formaldehyde treatment. The internal carotid artery is only sparsely innervated; however, it shows a dense sympathetic supply at the site of pressor receptors. Following removal of the superior cervical ganglion, a total loss of fluorescent adrenergic nerves occurs and degeneration of nerve endings possessing dense core vesicles is conspicuous. These nerve terminals are situated mainly subendothelially in the carotid body sinusoids; they only rarely terminate on type I cells.     

The superior laryngeal nerve and the superior laryngeal artery

Length, diameter and anastomoses of the nervus vagus and its ganglion inferius were measured 44 halved heads. On the average, 8.65 fiber bundles of the vagus nerve leave the retro-olivary area. In the area of the jugular foramen is the near superior ganglion of the 10th cranial nerve. In this area were found 1.48 (mean value) anastomoses with the 9th cranial nerve. 11.34 mm below the margo terminalis sigmoidea branches off the ramus internus of the accessory nerve which has a length of 9.75 mm. Further anastomoses with the 10th cranial nerve were found. The inferior ganglion of the 10th nerve had a length of 25.47 mm and a diameter of 3.46 mm. Five mm below the ganglion the 10th nerve had a width of 2.9 and a thickness of 1.5 mm. The mean length of the superior sympathetic ganglion was 26.6 mm, its width 7.2 and its thickness 3.4 mm. In nearly all specimens anastomoses of the superior sympathetic ganglion with the ansa cervicalis profunda and the inferior ganglion of the 10th cranial nerve were found. The superior laryngeal nerve branches off about 36 mm below the margo terminalis sigmoidea. The width of this nerve was 1.9 mm, its thickness 0.8 mm on the right and 1.0 mm on the left side. The division in the internal and external rami was found about 21 mm below its origin. Between the n. vagus and thyreohyoid membrane the ramus internus had a length of 64 mm, the length of external ramus between the vagal nerve and the inferior pharyngeal constrictor muscle was 89 mm. Its mean length below the thyreopharyngeal part was 10.7 mm, 8.6 branchlets to the cricothyroid muscle were counted. The superior laryngeal artery had its origin in 80% of cases in the superior thyroideal artery, in 6.8% this vessel was a branch of the external carotid artery. Its average outer diameter was 1.23 mm on the right side and 1.39 mm on the left. The length of this vessel between its origin and the thyreohyoid membrane was 34 mm. In 7% on the right side and in 13% on the left, the superior laryngeal artery reached the larynx through a foramen thyreoideum. Ranges of diameters and lengths of vessels and nerves in the larynx are given.     

Innervation of the parathyroid in the european starling (Sturnus vulgaris)

Anatomical studies were conducted to characterize the source, type, and distribution of parathyroid gland innervation in European starlings. Denervation experiments demonstrated that the parathyroid glands and adjacent carotid bodies are innervated by nerve fibers originating in the nodose ganglion of the vagus nerve. In the parathyroid parenchyma, these fibers terminate adjacent to chief cells or near vascular smooth muscle. Vagal fibers also form synapses with catecholamine-containing glomus cells of the carotid body. Blood that first perfuses the carotid body subsequently perfuses the parathyroid parenchyma. These observations suggest that vagal innervation may influence parathyroid function in starlings either through direct chief cell innervation or through alteration of vascular perfusion. A neurohemal relationship also may exist between the carotid body and parathyroids.     

Innervation of the carotid body. An experimental quantitative study

The innervation of the carotid body in the cat was studied by means of light- and electron-microscopic techniques. Sinus nerve resection, glossopharyngeal resection, bilateral cervical sympathectomy, excisions of two nerves, and injection of 6-hydroxydopamine (6-OH-DA) were performed in different groups of animals. It was found that resection of the sinus nerve produces a rapid phase of degeneration of intralobular fibers and synaptic boutons, followed by a reinnervation with a progressive reappearance of these elements. This reinnervation is retarded by sympathectomy and prevented by 6-OH-DA. It is therefore concluded that reinnervation is due to collateral regeneration of nearby sympathetic fibers. Resection of the sinus nerve produces an increase in the number of argentaffin cells and dense-cored vesicles in the cytoplasm of principal cells. These findings suggest the existence of efferent synaptic contacts between this nerve and principal cells. Part of the intralobular fibers and synaptic boutons degenerate after bilateral sympathectomy demonstrating that sympathetic axons connect synaptically to the principal cells. Sympathetic fibers reach the carotid body, not only from branches of the cervical plexuses but also from fibers running in the adventitia of the common carotid artery, and via glossopharyngeal and sinus nerves. The vagus nerve contributes a few fibers to the parenchymal lobules of the carotid body.     

Distribution of TRPVs,P2X3, and Parvalbumin in the Human Nodose Ganglion

Immunohistochemistry for several neurochemical substances, the transient receptor potential cation channel subfamily V member 1 (TRPV1) and 2 (TRPV2), P2X3 receptor, and parvalbumin (PV), was performed on the nodose ganglion, pharynx, and epiglottis in human cadavers. The nodose ganglion was situated beneath the jugular foramen, and had a spindle shape with the long rostrocaudal axis. The pharyngeal branch (PB) issued from a rostral quarter of the nodose ganglion, whereas the superior laryngeal nerve (SLN) usually originated from a caudal half of the ganglion. In the nodose ganglion, sensory neurons were mostly immunoreactive for TRPV1 (89 %) or P2X3 (93.9 %). About 30 % of nodose neurons contained TRPV2 (35.7 %)—or PV (29.9 %)—immunoreactivity (-IR). These neurons mainly had small to medium-sized cell bodies, and were distributed throughout the ganglion. Neurodegenerative profiles such as shrinkage or pyknosis could not be detected in the examined ganglion. Occasionally, TRPV2-IR nerve fibers surrounded blood vessels in the epiglottis as well as in the nasal and oral parts of the pharynx. Isolated TRPV2-IR nerve fibers were also located beneath the epithelium. TRPV1-, P2X3-, or PV-IR nerve endings could not be detected in the pharynx or epiglottis. In the PB and SLN, however, numerous nerve fibers contained TRPV1-, TRPV2-, P2X3-, and PV-IR. The present study suggests that TRPV1-, TRPV2-, P2X3-, and PV-IR neurons in the human nodose ganglion innervate the pharynx and epiglottis through the PB and SLN. These neurons may respond to chemical, thermal, and mechanical stimuli during respiration and swallowing.     

Tissue distribution and innervation pattern of peptide immunoreactivities in the rat pancreas.

The distribution of calcitonin gene-related peptide (CGRP), substance P/tachykinin (SP/TK), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) and gastrin-releasing peptide (GRP) immunreactivities (IR) in the rat pancreas was investigated using radioimmunoassay and immunohistochemistry. CGRP, NPY and VIP tissue contents are much higher than GRP and SP/TK concentrations. Peptide-containing nerves are distributed to both the exocrine and endocrine pancreas. However, differences exist in terms of density and targets of innervation for each peptidergic system. In the acini and through the stroma, fibers IR for CGRP, NPY and VIP are greater than GRP- and SP/TK-containing processes. The vasculature is supplied by a prominent NPY, CGRP and, to a lesser extent, SP/TK innervation. VIP-IR is found occasionally, and GRP-IR is never detected, in fibers associated with blood vessels. Around ducts, CGRP- and NPY-positive neurites are greater than SP/TK- greater than or equal to VIP-IR fibers, whereas GRP-containing nerves are not visualized. In the islets, the density of peptidergic nerves is: VIP-, GRP- greater than or equal to CGRP-IR greater than NPY or SP/TK. In intrapancreatic ganglia. VIP- and, to a lesser extent, NPY-IRs are found in numerous neuronal cell bodies and in nerve fibers; GRP-IR is present in numerous nerve processes and in few cell bodies; CGRP- and SP/TK-IRs are detected only in fibers wrapping around unlabeled ganglion cells. The majority of CGRP-IR fibers contain SP/TK-IR. The existence of differential patterns of peptidergic nerves suggests that peptides exert their effects on pancreatic functions via different pathways.     

Mash1 is required for glomus cell formation in the mouse carotid body

The carotid body consists of chemoreceptive glomus cells, sustentacular cells and nerve endings. The murine carotid body, located at the carotid bifurcation, is always joined to the superior cervical ganglion of the sympathetic trunk. Glomus cells and sympathetic neurons are immunoreactive for the TuJ1, PGP9.5, tyrosine hydroxylase (TH) and neuropeptide Y (NPY) markers. Glomus cells are also immunoreactive for serotonin (5-HT). A targeted mutation of Mash1, a mouse homolog of the Drosophila achaete-scute complex, results in the elimination of sympathetic ganglia. In Mash1 null mutant mice, the carotid body primordium forms normally in the wall of the third arch artery at embryonic day (E) 13.0 and continues to develop, although the superior cervical ganglion is completely absent. However, no cells in the mutant carotid body display the TuJ1, PGP 9.5, TH, NPY and 5-HT markers throughout development. The absence of glomus cells was also confirmed by electron microscopy. The carotid body of newborn null mutants is composed of mesenchymal-like cells and nerve fibers. Many cells immunoreactive for the S-100 protein, a sustentacular cell marker, appear in the mutant carotid body during fetal development. The Mash1 gene is thus required for the genesis of glomus cells but not for sustentacular cells.     

Enkephalin-like immunoreactivity in ganglionic cells in the larynx and superior cervical ganglion of the rat.

The distribution of enkephalin-like immunoreactivity (ENK-LI) in the larynx, the superior cervical ganglion (SCG) and the nodose ganglion of adult rats was examined in the present study. A substantial number of the local acetylcholinesterase (AChE)-positive, presumably parasympathetic, ganglionic cells in the larynx displayed ENK-LI. These cells also exhibited neuropeptide Y (NPY)- and vasoactive intestinal polypeptide (VIP)-LI. Varicose nerve fibers showing ENK-LI were observed close to the acini and ducts of the glands, in the perichondrium and in the lamina propria. The varicosities exhibiting ENK-LI frequently displayed NPY- and VIP-LI. The ENK-LI was detected in a subpopulation of AChE-positive nerve fibers in the laryngeal tissue. In the SCG, only a small number of the ganglionic cells displayed ENK-LI. These cells, in contrast to other ganglionic cells of the SCG, did not show NPY-LI. None of the ganglionic cells of the nodose ganglion exhibited ENK-LI. Sympathectomy and vagotomy affected neither the number nor the distribution of fibers showing ENK-LI in the larynx. In conclusion, ENK appears to be present together with NPY and VIP in the parasympathetic innervation of the larynx and in a very limited number of the ganglionic cells of a sympathetic ganglion, the SCG, of the adult rat.     

Evidence for GABAergic fibers entering the superior cervical ganglion of rat from the preganglionic nerve trunk

The origin of gamma-aminobutyric acid immunoreactive (GABA-IR) nerve fibers present in the superior cervical ganglion (SCG) of rat was investigated. With immunocytochemical techniques many nerve fibers showed GABA-like positivity in the cervical sympathetic trunk, whereas similar staining could not be revealed in the internal carotid nerve or in the external carotid nerve. Ligation of the cervical sympathetic trunk for 24 h resulted a dramatic reduction in the staining density in the ganglion and in the cervical sympathetic trunk distal to the ligature. After transection of the preganglionic nerve fibers for eleven days or more, very few fibers staining for GABA were seen in the ganglion. The immunohistochemical results suggest that a major source of GABA within the SCG is a population of GABAergic axons entering from the preganglionic trunk.     

Evidence for GABAergic fibers entering the superior cervical ganglion of rat from the preganglionic nerve trunk

Summary The origin of gamma-aminobutyric acid immunoreactive (GABA-IR) nerve fibers present in the superior cervical ganglion (SCG) of rat was investigated. With immunocytochemical techniques many nerve fibers showed GABA-like positivity in the cervical sympathetic trunk, whereas similar staining could not be revealed in the internal carotid nerve or in the external carotid nerve. Ligation of the cervical sympathetic trunk for 24 h resulted a dramatic reduction in the staining density in the ganglion and in the cervical sympathetic trunk distal to the ligature. After transection of the preganglionic nerve fibers for eleven days or more, very few fibers staining for GABA were seen in the ganglion. The immunohistochemical results suggest that a major source of GABA within the SCG is a population of GABAergic axons entering from the preganglionic trunk.     

An immunohistochemical study on the innervation of SP-IR nerves in the cerebral arteries of the bent-winged bat

Summary The overall distribution of substance P (SP) immunoreactive (IR) nerves surrounding the cerebral arteries of the bent-winged bat were investigated immunohistochemically. In this microchiropteran species, the walls from the vertebral artery to the caudal part of the basilar artery have considerably well-developed plexuses of SP-IR nerves, whereas no demonstrable SP-IR fibers were found in the crostral part of the basilar artery, and in more rostrally located arteries the nerve supply was very sparse or occasionally lacking. This innervation pattern has not yet been established for the cerebral arterial systems of other mammals that have been studied under normal conditions, but it is very similar to the pattern of SP-IR innervation observed in the guinea pig and cat of which the trigeminal ganglia have been destroyed. From the combination of this and other immunohistochemical findings, it is suggested that SP-IR nerves innervating the vertebral and basilar arteries of the bent-winged bat originate from the upper cervical dorsal root ganglia (DRG) and enter the cranial cavity along the vertebral artery and through the meninges.Abbreviations BA basilar artery - CSN cervical spinal nerves - ICS internal carotid system - SCG superior cervical ganglion - SNB sympathetic nerve bundle - VA vertebral artery - VBS vertebro-basilar system     

Origin and colocalization of CGRP- and SP-reactive nerves in cat airway epithelium.

A combination of neuroanatomic techniques was used to examine the origin and neuropeptide content of nerve fibers in the airway epithelium of adult cats. By the use of immunocytochemical methods, the peptides substance P (SP) and calcitonin gene-related peptide (CGRP) were colocalized in airway epithelial nerve fibers. Two days after wheat germ agglutinin (WGA) was injected into the nodose ganglion, fibers containing WGA immunoreactivity (IR) were detected in the airway epithelium. SP-like immunoreactivity (LI) and CGRP-LI were demonstrated separately in the WGA-IR fibers, establishing their origin from nerve cell bodies of nodose ganglion. Vagal transection inferior to the nodose ganglion reduced the number of SP- and CGRP-IR fibers by greater than 90% in ipsilateral airways. In contralateral airways, SP-IR fibers were substantially reduced, whereas the effect on CGRP-IR fibers was not statistically significant. Vagotomy superior to the nodose ganglion did not alter the density of peptide-IR fibers. The results prove that SP- and CGRP-IR nerve fibers of cat airway epithelium originate from nerve cell bodies in the nodose ganglion and that SP- and CGRP-like peptides may be stored together in some nerve fibers of the airway epithelium.     

Sympathetic innervation of the reproductive organs of the male opossum, Didelphis albiventris (Lund, 1841)

The dissection of nerves and ganglia anatomically related to the pelvic organs revealed one inferior mesenteric ganglion, two testicular ganglia, two hypogastric nerves, two pelvic ganglia and two pelvic nerves. The histochemical demonstration of catecholamines by a glyoxylic acid fluorescence method revealed a rich sympathetic innervation in the ductus deferens, in the three segments of the prostate and in the convoluted ductuli efferentes. The testis, epididymis and all three pairs of bulbourethral glands presented fluorescent nerve fibers only around blood vessels. Removal of the inferior mesenteric and testicular ganglia, and hypogastric neurectomy with our without ligature and sectioning of testicular arteries, had no effect on the density of the nonvascular fluorescent fibers. Removal of the periprostatic tissue caused complete denervation of the prostate and marked denervation of the ductuli efferentes and ductus deferens. Small ganglia containing fluorescent nerve cell bodies were found close to the capsule of the prostate. The results indicate that short adrenergic neurons are responsible for the sympathetic innervation of the reproductive organs of the male opossum.     

The Distribution of Transient Receptor Potential Melastatin-8 in the Rat Soft Palate, Epiglottis, and Pharynx

Immunohistochemistry for transient receptor potential melastatin-8 (TRPM8), the cold and menthol receptor, was performed on the rat soft palate, epiglottis and pharynx. TRPM8-immunoreactive (IR) nerve fibers were located beneath the mucous epithelium, and occasionally penetrated the epithelium. These nerve fibers were abundant in the posterior portion of the soft palate and at the border region of naso-oral and laryngeal parts of the pharynx. The epiglottis was free from such nerve fibers. The double immunofluorescence method demonstrated that TRPM8-IR nerve fibers in the pharynx and soft palate were mostly devoid of calcitonin gene-related peptide-immunoreactivity (CGRP-IR). The retrograde tracing method also demonstrated that 30.1 and 8.7 % of sensory neurons in the jugular and petrosal ganglia innervating the pharynx contained TRPM8-IR, respectively. Among these neurons, the co-expression of TRPM8 and CGRP-IR was very rare. In the nodose ganglion, however, pharyngeal neurons were devoid of TRPM8-IR. Taste bud-like structures in the soft palate and pharynx contained 4–9 TRPM8-IR cells. In the epiglottis, the mucous epithelium on the laryngeal side had numerous TRPM8-IR cells. The present study suggests that TRPM8 can respond to cold stimulation when food and drinks pass through oral and pharyngeal cavities.     

Excitatory effects of 5-hydroxytryptamine, veratridine and phenyl diguanide on sensory ganglion cells of the nodose ganglion of the cat

5-hydroxytryptamine (5-HT), phenyl diguanide (PDG) and veratridine, injected into the common carotid artery in doses of 5–10 μg, caused action potentials to be generated in small bundles dissected from the infranodose vagus nerve of cat. These excitatory effects persisted following transection of the supranodose vagus nerve. 5-HT and PDG also produced action potentials in fibers dissected from the supranodose vagus, before and after transection of the cervical vagus nerve; veratridine was not tested on these fibers. Not all infranodose or supranodose fibers were excited by these drugs in the doses used. Susceptibility of the fibers to 5-HT, PDG or veratridine did not appear to be related to the type of sensory modality transmitted by the fibers, as fibers subserving different modalities were excited. Pentobarbital, 1–4 mg/kg injected intravenously, depressed responses to 5-HT (responses that the reflexes produced by 5-HT, PDG and veratridine through an action on the nodose ganglion probably result from direct excitatory effects of these drugs on sensory ganglion cells.