Lingual Branch Research Articles

Parasympathetic postganglionic cells in the glossopharyngeal nerve trunk and their relationship to unmyelinated nerve fibers in the fungiform papillae of the frog

The glossopharyngeal nerve of the frog is made up of afferent nerve fibers and efferent, parasympathetic and sympathetic nerve fibers. The precise origin and course of the parasympathetic efferent nerve fibers in the fungiform papillae of the frog's tongue were investigated. We found the ganglionic cells in the lingual branch of the frog glossopharyngeal nerve. The surface of the ganglionic cell bodies was partly covered by synaptic endings that impinged upon it. Synaptic endings contained clear synaptic vesicles and large dense-cored vesicles. After cutting of the glossopharyngeal nerve proximal to the jugular ganglion, synaptic endings were found to show definite signs of degeneration. These findings led us to the conclusion that the ganglionic cells in the lingual branch of the glossopharyngeal nerve are the parasympathetic postganglionic cells. After cutting of the glossopharyngeal nerve distal to the jugular ganglion, some unmyelinated nerve fibers in the fungiform papillae and postganglionic cells in the lingual branch remained intact. These results strongly suggest that the origin of some of the unmyelinated nerve fibers is the parasympathetic postganglionic cell in the lingual branch.

Early development and innervation of taste bud‐bearing papillae on the rat tongue

Early development of fungiform papillae on the fetal rat tongue was examined: (1) to determine whether morphogenesis of the taste bud-bearing fungiform papillae is induced by nerve and (2) to study the growth pattern of the two sensory nerves that innervate the papilla. The papillae first appear on the 15th day of gestation (E15; E1 is the day when the dam is sperm positive) in rows parallel to the midline sulcus. There appears to be a medial-lateral and an anterior-posterior gradient in the sequence of papilla differentiation. The epithelium of the early papilla resembles a multilayered placode topped by a flattened surface periderm. Close examination of the peridermal cells at the apex of the papillae reveals that the cells have fewer surface microvilli and their cytoplasm is more electron opaque than that of similar cells in interpapillary regions. The basal cells in the placode-like epithelium differ from those in interpapillary regions in that they are postmitotic and have more mitochondria. At later stages, the papilla acquires a mesenchymal core and nerves grow into the core. Results from organ culture experiments of tongue fragments taken from E14 fetuses indicate that morphogenesis of fungiform papillae is initiated in the absence of sensory nerve influence, but the nerve exerts a trophic effect on their maintenance. The two sensory nerves of the tongue, the chorda tympani and the lingual branch of the trigeminal nerve, enter the tongue mesenchyme at E14 and grow toward the epithelium. By E15 the chorda tympani branches have reached the developing fungiform papillae, by E16 many have entered the papilla, and by E17 they have penetrated the epithelium at the papilla apex. Their fibers are associated exclusively with the cells at the papilla apex, where the taste bud will develop. The trigeminal nerve ramifies beneath the surface of the entire epithelium by E15. Later, it, too, sends branches into fungiform papillae; these ascend along the trunk of the chorda tympani and at E17 terminate in the connective tissue core around the chorda tympani field. The results are compatible with the notion that the tongue epithelium exerts a general tropic effect on growing axons of both sensory nerves, and the epithelial cells of the fungiform papilla apex exert a similar effect to which only the chorda tympani axons are responsive.

Peripheral and central terminations of hypoglossal afferents innervating lingual tactile mechanoreceptor complexes in Fringillidae

Injections of cholera toxin B subunit conjugated to horseradish peroxidase (CTB-HRP) were made into the lingual branch of the hypoglossal nerve in four species of finch in order to identify the innervation of the mechanoreceptors of the dermal papillae of the tongue, and simultaneously to determine the pattern of central projections of lingual hypoglossal afferents. The results showed that hypoglossal fibers innervate all the Herbst corpuscles and terminal cell receptors of the elaborately organized papillae of the dorsum of the tongue, of the shorter papillae in the ventral tongue, and the loose collection of Herbst corpuscles in the subpapillary region. Labelled fibers were also observed in the intralingual glands, in the intrinsic tongue muscles, and in the posterodorsal epithelium where they formed budlike structures. Retrogradely labelled cell bodies were located in the jugular ganglion and their central processes ascended and descended throughout the brainstem within the descending trigeminal tract (TTD). Terminal fields were observed within the dorsolateral part of the nucleus caudalis of TTD, predominantly ipsilaterally, and within the medial part of the dorsal horn of the first 4-6 cervical segments bilaterally. There were dense patches of termination over a dorsolateral subnucleus of the interpolated nucleus of TTD, and within two regions of the principal sensory trigeminal nucleus: a large one laterally and a small one medially. Terminal fields were also observed within the nucleus ventralis lateralis anterior of the rostral solitary complex, and within adjacent nuclei, which are probably equivalent to the dorsal sensory nuclei of the facial and glossopharyngeal nerves of other avian species. The results are interpreted in the light of the role of the tongue in species-specific patterns of feeding in finches, and the possible requirement for the central integration of touch and taste.

Centrifugal decrement in diameter of myelinated afferent fibres innervating frog taste organ

1. 1. Regional changes in the diameter of single myelinated afferent nerve fibres innervating the taste disc of the fungiform papillae on the bullfrog tongue were investigated morphologically and functionally. 2. 2. The diameter of myelinated afférents in the medial lingual branch of the glossopharyngeal nerve averaged 8.4 μm at the proximal end of the tongue and gradually decreased at the rate of 0.8 μm/cm length of the fibres as they ran in the apical direction of the tongue. 3. 3. The conduction velocity of single myelinated afferent fibres within the tongue decreased gradually as they ran peripherally. 4. 4. Electrophysiological inspection of neural connections between the fungiform papillae suggests that a gradual centrifugal decrease in the diameter of a single myelinated afferent fibre is not due to multiple bifurcations of the fibre at various sites within the tongue, but due to a natural gradual decrease in the thickness of the myelin sheath and the diameter of axon.

The chorda tympani and glossopharyngeal nerves in the adult hamster

The numbers and diameters of axons in the intact chorda tympani (CT) and lingual branch of the glossopharyngeal nerve (GN) are quantified with the use of electron microscopic photomontages. The cross-sectional diameters of the CT and GN average 68 and 86 microns, respectively. The intact CT contains ˜ 1050 fibers, 63% are unmyelinated and 37% are myelinated. The GN contains ˜ 1600 fibers, 79% are unmyelinated and 21% are myelinated. Both nerves are made up of relatively small unmyelinated and myelinated fibers, although the GN shows a broader distribution of diameters for its myelinated fibers due to the presence of general somatosensory fibers. Following de-efferentation, there is a 48% reduction in the number of unmyelinated fibers in the CT. Fifty-two per cent of the unmyelinated fibers are sensory. The number of myelinated fibers is not significantly reduced and nearly all of the myelinated fibers are sensory. Sixty-seven per cent of the fibers within the CT are sensory. The de-efferented CT contains an equal number of unmyelinated and myelinated axons and a total of ˜ 700 fibers. Comparable data in the rat indicate that its intact and de-efferented CT are organized differently in regards to the numbers of sensory and motor, and myelinated versus unmyelinated fibers. The findings of the present study, together with the available data from other species, suggest that anatomical differences in the make-up of the major gustatory nerves do not contribute in any obvious way to the known differences in the response properties between the rat and hamster CT, and that the number of myelinated fibers in the visceral motor component of the CT varies considerably across species.

Radio-anatomic study of the carotid axis with regard to the implantation of microsurgical vascular anastomoses.

The authors report a radio-anatomic study of the carotid axis in the context of the implantation of microsurgical vascular anastomoses. The information derived from 36 dissections and 50 arteriographic studies suggests the preferential use of the superior thyroid, facial and lingual branches. Section and turning-down of the external carotid and direct end-to-side implantation on the common carotid could provide fall-back solutions when the collaterals are slender. Because of anatomic variations and frequent atheromatous lesions, arteriographic study before implantation appears essential.

EFFECTS OF I.A. LIGNOCAINE ON ADRENALINE-INDUCED VASOCONSTRICTION

The effects of i.a. administered lignocaine on the in vivo response of the vascular bed supplied by the lingual, external maxillary and posterior auricular branches of the common carotid artery were studied in the rat. Infusions of lignocaine in concentrations of 10-1000 micrograms ml-1 administered at the rate of 0.05 ml min-1 for 10 min did not affect vascular resistance or arterial pressure in the common carotid artery. However, following such infusions, the increase of vascular resistance caused by bolus doses of adrenaline (20-120 ng in 0.1 ml) was inhibited, indicating lignocaine-adrenaline antagonism. Responses to adrenaline remained significantly depressed 60 min after the termination of a 100-micrograms ml-1 or higher lignocaine infusion.

Glossopharyngeal and tectal influences on tongue-muscle motoneurons in the Japanese toad

Anuran tongue-muscle motoneurons receive excitatory inputs both from the glossopharyngeal nerve afferents and from the optic tectum. As a step toward elucidating the neural bases for controlling the tongue movements, we searched intracellularly for the neuronal pathways from the glossopharyngeal afferents to the tongue-muscle motoneurons in paralyzed Japanese toads. The electrical stimuli applied to the glossopharyngeal nerve (ipsilateral lingual branch) evoked polysynaptic excotatory postsynaptic potentials (EPSPs) in tongue-protractor motoneurons and mixed mono- and polysynaptic EPSPs in tongue-retractor motoneurons. Furthermore, we investigated the mode of the convergency of the excitatory inputs from the glossopharyngeal nerve and those from the optic tectum. A spatial facilitation was observed between the tectal EPSPs and the glossopharyngeal EPSPs in some motoneurons tested. These results suggest the existence of common excitatory premotor interneurons, on which the tectal descending volleys and the glossopharyngeal afferent volleys converge.

Cat carotid bodies reinnervated by normal or foreign nerves

The carotid body of the cat was reinnervated with either its native nerve, the carotid sinus nerve (CSN, re-anastomosis), or a foreign nerve, the lingual branch of the IXth cranial nerve (LN, cross-anastomosis). In both types of preparations, regenerating axons from the LN or CSN readily penetrated carotid body parenchymal tissue, as demonstrated by axoplasmic transport of radiolabeled material from the petrosal (sensory) ganglion. Electron microscopy revealed nearly normal fiber invasion into lobules of glomus (type I) and sustentacular (type II) cells following reinnervation by either the foreign or native nerve. However, while the regenerated CSN fibers formed a normal complement of specialized axon terminals in contact with type I cells, the incidence of such terminals in LN reinnervated carotid bodies was reduced by over 90% (2–19 months survival time). This low incidence of specialized LN endings was correlated with reductions in the magnitude of the chemosensory discharge elicited in these preparations by asphyxia, NaCN or acetylcholine. These data suggest that chemosensitivity depends upon intimate association between glomus cells and afferent nerve endings; and that the ability to form such contacts may reside in particular axons whose incidence is higher in the CSN than in the LN.

Two distinct projection areas from tongue nerves in the frontal operculum of macaque monkeys as revealed with evoked potential mapping

Projection areas in the cerebral cortex from tongue nerves were investigated in anesthetized macaque monkeys ( Macaca fuscata). Three tongue nerves (lingual nerve, chorda tympani, and a lingual branch of the glossopharyngeal nerve) were electrically stimulated and thereby evoked mass field potentials were recorded with microelectrodes roving through the exposed and buried frontal operculum. Two distinct tongue nerve projection areas were thus located; one in the lower part of the precentral gyrus ventral to the inferior precentral sulcus, and the other in the medial part of the buried frontal operculum. The former corresponds to the “cortical masticatory area”, previously defined in macaque monkeys as involved in somatic sensation as well as mastication. However, the prominent projection from the chorda tympani and glossopharyngeal nerve branch, containing taste fibers, to this area suggests its involvement in taste sensation. The latter corresponds to the “pure gustatory area” defined in squirrel monkeys in both location and cytoarchitecture. However, projection to this area from the lingual nerve, which contains only somatic nerve fibers, suggests its involvement in somatic sensation, as well.

Late onset of mandibular and lingual dysesthesia secondary to postextraction infection

A ltered or impaired sensation of the distribution of the inferior alveolar and lingual branches of the trigeminal nerve is most commonly associated with complications of mandibular third molar surgery. Numerous reports and reviews of this problem reveal, however, that the late onset of impaired sensation is uncommon and that nerve dysfunction related to postsurgical infection is unusual. Three cases will be reported in this article, with a discussion of the possible pathophysiologic mechanism of injury, Therapy and prognosis for recovery will also be discussed.

Anatomy of the gustatory system in the hamster: central projections of the chorda tympani and the lingual nerve.

The sensory modalities of taste and touch, for the anterior tongue, are relegated to separate cranial nerves. The lingual branch of the trigeminal nerve mediates touch: the chorda tympani branch of the facial nerve mediates taste. The chorda tympani also contains efferent axons which originate in the superior salivatory nucleus. The central projections of these two nerves have been visualized in the hamster by anterograde labelling with horseradish peroxidase (HRP). Afferent fibers of the chorda tympani distribute to all rostral-caudal levels of the solitary nucleus. They synapse heavily in the dorsal half of the nucleus at its rostral extreme; synaptic endings are sparser and located laterally in caudal regions. These taste afferents travel caudally in the solitary tract and reach different levels by a series of collateral branches which extend medially in the the solitary nucleus, where they exhibit preterminal and terminal swellings. Taste afferent axons range in diameter from 0.2 micrometer to 1.5 micrometers. The thickest axons project exclusively to the rostral and intermediate subdivisions of the solitary nucleus; the find ones may distribute predominantly to the caudal subdivision. Afferent fibers of the lingual nerve terminate heavily in the dorsal one-third of the spinal nucleus of the trigeminal nerve and also as a dense patch in the lateral solitary nucleus at the midpoint between its rostral and caudal poles. This latter projection overlaps that of the chorda tympani. Thus the two sensory nerves which subserve taste and touch from coincident peripheral fields on the tongue converge centrally on the intermediate subdivision of the solitary nucleus. Efferent neurons of the superior salivatory nucleus were labelled retrogradely following application of HRP to the chorda tympani. These cells are located ipsilaterally in the medullary reticular formation ventral to the rostral pole of the solitary nucleus; their dendrites are oriented dorsoventrally. The efferent axons course dorsally, form a genu lateral to the facial somatomotor genu, and course ventrolaterally through the spinal nucleus of the trigeminal nerve to exit the brain ventral to the entering facial afferents.

Effects of nitroglycerin on the diameter of intracranial and extracranial arteries in monkeys.

• Nitroglycerin is widely used as a safe and effective dilator of the large coronary arteries in patients with ischemic heart disease. Little is known, however, about its effects on the intracranial arteries. We compared, in the monkey, the effects of intravenous (IV) nitroglycerin, alone and in combination with phenylephrine hydrochloride, on the diameter of the intracranial portion of the internal carotid artery, the middle cerebral artery, and the lingual branch of the external carotid artery; IV nitroglycerin increased the diameter of all three. These arteries remained dilated even when phenylephrine was added to the infusion to raise the mean arterial pressure by up to 29% above control values.

Lingual Mechanoreceptive Information II

The extent to which the known trigeminothalamic projections are related to afferents from specific peripheral branches of the trigeminal nerve is not clearly revealed by degeneration studies involving lesions of the various trigeminal nuclei. This study examines the ascending projections related to the lingual branch of the trigeminal nerve using the evoked-potential technique in pentobarbital anesthetized rhesus monkeys. The distribution of potentials within the medulla, pons, and midbrain was determined by recording with macroelectrodes following single-pulse stimulation of the lingual nerve. Results show that two pathways from the main sensory nucleus convey lingual nerve information to the thalamic ventral posteromedial nucleus: an ipsilateral projection which in position corresponds to the dorsal trigeminal tract, and a larger contralateral projection which in position corresponds to the to the crossed ventral trigeminal tract, or trigeminal lemniscus. Additionally, the spinal trigeminal nucleus contributes fibers of lingual nerve origin to the contralateral medial lemniscus. The role of low-threshold mechanoreceptive information in lingual sensorimotor activity is discussed in relation to current concepts of somatosensory system function.

Intraoral nerve block for glossopharyngeal neuralgia

Glossopharyngeal neuralgia was treated by a new method of intraoral block. The procedure consists of block for the tonsillar branch and block of the lingual branch by the injection of 5% Phenol in Glycerin. This can be applied for neuralgia with a trigger zone around the tonsil. The result is quite satisfactory. This is extremely safe and simple, and can be performed repetitively when recurrences occur. Also, this procedure does not preclude later operations as a final step.

Effects of antidromic activity in gustatory nerve fibers on taste disc cells of the frog tongue

Antidromic electrical stimulation of the lingual branch of the glossopharyngeal (IX) nerve of the frog was carried out while recording intracellular potentials of taste disc cells.

Branched chorda tympani neurons and interactions among taste receptors.

AbstractThe preterminal branching pattern of nerve fibers from the chorda tympani nerve was examined in the tongues of rats using a normal silver stain. The lingual branch of the trigeminal nerve was sectioned unilaterally proximal to where it is joined by the chorda tympani and these fibers were allowed to degenerate from eight to ten days prior to sacrifice of the animals. Termination of the chorda tympani fibers in the anterior tongue was found to be limited to the taste bud region of the fungiform papillae. The control side of the tongue showed ubiquitous fiber terminations in the basal layers of the common epithelium of the filiform papillae as well as in the lateral walls of the fungiform papillae. These fibers were assumed to be of trigeminal origin. Seventy‐nine percent of the fungiform papillae on the experimental side of the tongue received fibers from a branched nerve bundle. Branch points within the nerve bundles were located deep within the tongue 300–500 μ below the taste bud in 43% of the papillae, at the base of 36% of the fungiform papillae about 125 μ below the taste bud, and within the papilla.These data corroborate electrophysiological observations that single chorda tympani fibers receive input from more than one taste bud. Lateral inhibition observed among adjacent taste buds has been postulated to result from interaction of fiber inputs at branch points in the afferent fiber. From a theoretical consideration of the morphology of chorda tympani nerve fibers it is concluded that modification of the neural response may be feasible at branch points.

Subclavian-external carotid bypass graft for cerebrovascular insufficiency

In patients with occlusion of the common carotid artery, the external carotid artery is often kept open by collateral flow through the superior thyroid and lingual branches. If there is no surgically correctable lesion in the opposite carotid vessels, revascularization of the external carotid artery can provide a sufficient increase in collateral blood flow to relieve symptoms of cerebrovascular insufficiency. In three patients with occlusion of the common carotid artery, subclavian-external carotid artery bypass grafts were inserted. Each patient exhibited clinical improvement during follow-up periods ranging from twenty to forty-two months.

Trigeminal nerve inputs and central blood pressure change in the cat

Peripheral nerve stimulations produce blood pressure responses in nembutalized cats. A comparison is made between the effects of femoral nerve stimulation and stimulation of the pulpal and lingual branches of the trigeminus. Trigeminal nerve irritation produces a depressor response, and the femoral nerve mainly produces a pressor response.

Solitary neurons in human tongue.

AbstractMany solitary neurons, each encapsuled by a number of satellite cells and surrounded by collagenic fibers and unaccompanied by other nerve cells, are observed in specimens of the posterior third of the human tongue. They are ganglion cells of the parasympathetic nervous system supplying postganglionic fibers that are adenomotor to von Ebner's gland and myomotor to the smooth muscle of blood vessels. The occurence of solitary neurons suggests that a “ganglion” may consist of a single nerve cell. It is emphasized that the lingual branch of the glossopharyngeal nerve supplying the posterior third of the human tongue is not a sensory but a mixed nerve.