Search

The chorda tympani typically utilises the lingual nerve and submandibular ganglion to transmit parasympathetic fibres to the submandibular gland. During a routine anatomy dissection, the submandibular gland was found to be innervated by both the lingual nerve and the nerve to mylohyoid. The clinical implications of this variant dual innervation to the submandibular gland is not clear due to its rarity: however, recognising such a variation should be borne in mind during surgical intervention near the nerve to mylohyoid.

Introduction: The lingual nerve is a branch from posterior trunk of mandibular nerve and is sensory to the tongue, lingual gingivae and conveys postganglionic secretomotor fibres to submandibular, sublingual and anterior lingual glands. The nerve is joined by the chorda tympani branch of the facial nerve, and often by a branch of the inferior alveolar nerve. Submandibular ganglion is connected to the lingual by anterior and posterior filaments.1 Communications between Lingual nerve (LN) and Mylohyoid nerve (MHN) may be the possible explanation for the functional recovery of LN when its get injured during third molar extraction.4 Materials and Methods: A study was carried out in twenty embalmed cadavers and forty lingual nerves were studied by standard dissection method. Results: out of forty lingual nerves studied one lingual nerve was found to be arising from two roots. Anterior (AR) & posterior (PR). Mylohyoid nerve was found to be connected with the submandibular ganglion by two roots (anterior and posterior) and later was found to join the lingual nerve. A CB from LN joined posterior root. Discussion: Kim et al. described the communication between MHN & LN in 12.5% of 32 heads and first mentioned that this communication could provide another route of sensory transmission, being a possible cause of incomplete anaesthesia during dental practice.6 Conclusion: Our study showed multiple variations in one specimen which included variation in its origin (partly taking origin from anterior division of MN along with posterior division), communication with MHN, MHN was connected to submandibular ganglion by two roots. The incidences of all these variations in our study were 2.5%. Keywords: Lingual nerve, Inferior alveolar nerve, Mylohyoid nerve, Submandibular ganglion.

Neuronal signaling is known to be required for salivary gland development, with parasympathetic nerves interacting with the surrounding tissues from early stages to maintain a progenitor cell population and control morphogenesis. In contrast, postganglionic sympathetic nerves arrive late in salivary gland development to perform a secretory function; however, no previous report has shown their role during development. Here, we show that a subset of neuronal cells within the parasympathetic submandibular ganglion (PSG) express the catecholaminergic marker tyrosine hydroxylase (TH) in developing murine and human submandibular glands. This sympathetic phenotype coincided with the expression of transcription factor Hand2 within the PSG from the bud stage (E12.5) of mouse embryonic salivary gland development. Hand2 was previously associated with the decision of neural crest cells to become sympathetic in other systems, suggesting a role in controlling neuronal fate in the salivary gland. The PSG therefore provides a population of TH-expressing neurons prior to the arrival of the postganglionic sympathetic axons from the superior cervical ganglion at E15.5. In culture, in the absence of nerves from the superior cervical ganglion, these PSG-derived TH neurons were clearly evident forming a network around the gland. Chemical ablation of dopamine receptors in explant culture with the neurotoxin 6-hydroxydopamine at early stages of gland development resulted in specific loss of the TH-positive neurons from the PSG, and subsequent branching was inhibited. Taken altogether, these results highlight for the first time the detailed developmental time course of TH-expressing neurons during murine salivary gland development and suggest a role for these neurons in branching morphogenesis.

The ability to monitor the release of neurotransmitters during synaptic transmission would significantly impact the diagnosis and treatment of neurological diseases. Here, we present a DNA-based enzymatic nanosensor for quantitative detection of acetylcholine (ACh) in the peripheral nervous system of living mice. ACh nanosensors consist of DNA as a scaffold, acetylcholinesterase as a recognition component, pH-sensitive fluorophores as signal generators, and α-bungarotoxin as a targeting moiety. We demonstrate the utility of the nanosensors in the submandibular ganglia of living mice to sensitively detect ACh ranging from 0.228 to 358 μM. In addition, the sensor response upon electrical stimulation of the efferent nerve is dose dependent, reversible, and we observe a reduction of ∼76% in sensor signal upon pharmacological inhibition of ACh release. Equipped with an advanced imaging processing tool, we further spatially resolve ACh signal propagation on the tissue level. Our platform enables sensitive measurement and mapping of ACh transmission in the peripheral nervous system.

This protocol provides a detailed decription of the experimental procedure, including nanosensor farbication and characterization, in vivo microinjection, and in vivo imaging of acetylcholine release in the submandibular ganglion of mice.

We performed endoscopic transoral neurectomy of the submandibular and sublingual glands to treat drooling. We bilaterally operated two adult cases with treatment-resistant drooling. In these patients, conventional treatment had failed. Repeated botilinum toxin type A (BOTOX®, Abdi Ibrahim Pharmaceutical Company, Istanbul, Turkey) injections had been effective but were becoming less so. The patients benefited from surgery in that their saliva scores decreased. No issue emerged over 6 months of follow-up. Endoscopic transoral neurectomy of the submandibular and sublingual glands reduces saliva production and allows management of drooling in treatment-resistant patients. Laryngoscope, 127:1604–1607, 2017

The submandibular ganglion (SMG) contains parasympathetic neurons which innervate the submandibular gland. In this study, immunohistochemistry for vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), choline acetyltransferase (ChAT), dopamine β-hydroxylase (DBH), tyrosine hydroxylase (TH), and the transient receptor potential cation channel subfamily V members 1 (TRPV1) and 2 (TRPV2) was performed on the human SMG. In the SMG, 17.5 % and 8.9 % of parasympathetic neurons were immunoreactive for VIP and TRPV2, respectively. SMG neurons mostly contained ChAT- and DBH-immunoreactivity. In addition, subpopulations of SMG neurons were surrounded by VIP (69.6 %)-, TRPV2 (54.4 %)- and DBH (9.5 %)-immunoreactive (-ir) nerve fibers. SMG neurons with pericellular VIP- and TRPV2-ir nerve fibers were significantly larger than VIP- and TRPV2-ir SMG neurons, respectively. Other neurochemical substances were rare in the SMG. In the human submandibular gland, TRPV1- and TRPV2-ir nerve fiber profiles were seen around blood vessels. Double fluorescence method also demonstrated that TRPV2-ir nerve fiber profiles were located around myoepithelial and acinar cells in the submandibular gland. VIP and TRPV2 are probably expressed by both pre- and post-ganglionic neurons innervating the submandibular and sublingual glands. VIP, DBH and TRPV2 may have functions about regulation of salivary components in the salivary glands and neuronal activity in the SMG.

Variations in the branching pattern of the mandibular nerve frequently accounts for failure to obtain adequate local anesthesia in routine oral and dental procedures, and also for unexpected injury to the nerves during surgery. The knowledge of the neurovascular relationships of the infratemporal region is relevant in odontostomatology practice. In this article we present a rare case of atypical communication between the inferior alveolar nerve and lingual nerve and the mylohyoid and lingual nerves. Further, the clinical implications of these communications on the development of the supplementary innervation and their possible role in anesthesia is discussed in detail. The communication between mylohyoid and lingual nerve was found in this case near the submandibular ganglion after the lingual nerve passes in close relation to third molar tooth, which makes it more susceptible to injury during third molar extractions. The communicating branch between the mylohyoid nerve and lingual nerve may also innervate the tongue, and surgeons should be aware of this variation to avoid post- operative complcations after oral surgeries. Thus the precise anatomy of structures of infratemporal region and its variations may prove beneficial to clinicians, especially to oral and maxillofacial surgeons.

The major goals of this present study were 1) to further clarify which parasympathetic ganglion sends postganglionic fibers to the lower gingiva and lip that may be involved in the inflammatory processes besides the local factors; 2) to separately examine the central pathways regulating sympathetic and parasympathetic innervation; and 3) to examine the distribution of central premotor neurons on both sides. A retrogradely transported green fluorescent protein conjugated pseudorabies virus was injected into the lower gingiva and lip of intact and sympathectomized adult female rats. Some animals received virus in the adrenal medulla which receive only preganglionic sympathetic fibers to separately clarify the sympathetic nature of premotor neurons. After 72–120 h of survival and perfusion, the corresponding thoracic part of the spinal cord, brainstem, hypothalamus, cervical, otic, submandibular and trigeminal ganglia were harvested. Frozen sections were investigated under a confocal microscope. Green fluorescence indicated the presence of the virus. The postganglionic sympathetic neurons related to both organs are located in the three cervical ganglia, the preganglionic neurons in the lateral horn of the spinal cord on ipsilateral side; premotor neurons were found in the ventrolateral medulla, locus ceruleus, gigantocellular and paraventricular nucleus and perifornical region in nearly the same number on both sides. The parasympathetic postganglionic neurons related to the gingiva are present in the otic and related to the lip are present in the otic and submandibular ganglia and the preganglionic neurons are in the salivatory nuclei. Third order neurons were found in the gigantocellular reticular and hypothalamic paraventricular nuclei and perifornical area.

The present immunohistochemical study was attempted to localize in the submandibular glands of mice at various postnatal stages a diacylglycerol kinase (DGK) isoform termed DGKζ which is characterized by a nuclear localization signal and a nuclear export signal. This attempt was based on following facts: the continuous postnatal differentiation of glandular cells in the rodent submandibular gland, the regulatory role of DGK in the activity of protein kinase C (PKC) through attenuation of diacylglycerol (DAG), and the possible involvement of PKC in various cellular activities including the saliva secretion as well as the cell differentiation. As a result, a selective localization of immunoreactivity for DGKζ was detected in terminal tubule (TT) cells which comprise a majority of the newborn acinar structure and differentiate into the intercalated duct cells and/or the acinar cells. The immunoreactivity was deposited in portions of the cytoplasm lateral and basal to the nucleus, but not in the nuclei themselves. Although the immunoreactive TT cells remained until later stages in female specimen than in male, they eventually disappeared in both sexes by young adult stages. The present finding suggests that the regulatory involvement of DGKζ in PKC functions via control of DAG is exerted in the differentiation of the TT cells. In addition, another possible involvement of DGKζ in the regulation of secretion of the TT cells as well as its functional significance of its nuclear localization in the submandibular ganglion cells was also discussed.

Schwannoma is a benign nerve sheath tumor composed of Schwann cells. Schwannomas originating from ganglia are rare, and schwannomas of the submandibular ganglion or glandular branches have not been reported to date. We present a case of a Japanese woman in her sixties with a submandibular schwannoma originating from the submandibular ganglion, mimicking a submandibular gland tumor on radiological findings. As the radiological findings were nonspecific, the key finding in the present case may be the characteristic location of the tumor suspended from the undersurface of the lingual nerve and situated above the deep portion of the submandibular gland.

Background and objectives: An anatomical site in the oral cavity can be used to trigger the jaw opening reflex in patients with pseudobulbar palsy who have difficulty opening the mouth. The site is located at the midpoint between the palatoglossal arch and pterygomandibular fold and medial to the retromolar pad. However, previous findings on the nerves innervating this particular area are inconsistent. Therefore, in this study, we carefully investigated the sensory nerves that innervate the area near the trigger point of the jaw opening reflex. Materials and methods: For the morphological investigation of sensory innervation in this area, in this study we exposed the cranial nerves in 26 halves of cadaver head and observed their distribution in soft tissue. Results: In all cases, several nerve fibers diverged anteroinferiorly from the lingual nerve located between its junction with the chorda tympani nerve and the junction with the communicating branch of the submandibular ganglion. These nerve fibers, thought to be the facial branches of the lingual nerve, innervated the mucosa in the vicinity of the palatoglossal arch, retromolar pad, and the lingual gingiva of the last molar which were near to the trigger point of the jaw opening reflex. Conclusion: The results suggest that the sensory nerve that induces the jaw opening reflex appears to be the branches to isthmus of fauces diverged from the lingual nerve.

TRPC (transient receptor potential cation channel subfamily C) members are nonselective monovalent cation channels and control Ca2+ inflow. In this study, immunohistochemistry for TRPC1, TRPC3, and TRPC4 was performed on rat oral and craniofacial structures to elucidate their distribution and function in the peripheries. In the trigeminal ganglion (TG), 56.1, 84.1, and 68.3% of sensory neurons were immunoreactive (IR) for TRPC1, TRPC3, and TRPC4, respectively. A double immunofluorescence method revealed that small to medium-sized TG neurons co-expressed TRPCs and calcitonin gene-related peptide. In the superior cervical ganglion, all sympathetic neurons showed TRPC1 and TRPC3 immunoreactivity. Parasympathetic neurons in the submandibular ganglion, tongue, and parotid gland were TRPC1, TRPC3, and TRPC4 IR. Gustatory and olfactory cells were also IR for TRPC1, TRPC3, and/or TRPC4. In the musculature, motor endplates expressed TRPC1 and TRPC4 immunoreactivity. It is likely that TRPCs are associated with sensory, autonomic, and motor functions in oral and craniofacial structures.

The route of fine fascicles of nerve fibers in the lingual nerve was clarified. Contemporary anatomy textbooks describe the lingual nerve as supplying sensory innervation to the mucous membrane of the presulcal part of the tongue, the floor and side wall of the mouth, and the mandibular gums. In addition to receiving the chorda tympani and a branch of the inferior alveolar nerve, the lingual nerve is connected to the submandibular ganglion by a few branches. It carries preganglionic fibers from the chorda tympani and postganglionic fibers from the submandibular ganglion to the submandibular and sublingual glands. The branch from the mylohyoid nerve is described as a sensory nerve. However, we observed that this branch was directly connected to the submandibular ganglion. Furthermore, the branch from the submandibular ganglion innervated thin membranous tissue that originated in the petrous part of the temporal bone and inserted into the lateral surface of the superior constrictor. These branches have not been described in the anatomy textbooks and literature. Therefore, we studied the morphological features of the lingual nerve and discovered the route of fine fascicles of nerve fibers in the lingual nerve. These findings will likely improve the neurological and physiological understanding of the function of the lingual nerve.

Background: The management of sialorrhea can be difficult for both the patient and the clinician. Current management includes behavioral modification, anticholinergics, botulinum injections, and a variety of surgical options, which all have demonstrated some efficacy. As minimally invasive procedures flourish, we explore the feasibility of highly selective transoral submandibular neurectomy (TOSN) for the management of sialorrhea. Methods: Ten human cadaver dissections of the floor of mouth were performed bilaterally, for a total of 20 separate cases. An intraoral technique for highly selective, submandibular ganglion neurectomy is demonstrated. Results: A transoral submandibular ganglion neurectomy was performed in 10 cadavers (20 neurectomies) easily and reliably, without injury to the submandibular duct or the main trunk of the lingual nerve. Conclusion: Transoral submandibular neurectomy is an attractive addition to the armamentarium of surgical options for the treatment of medically intractable sialorrhea. Further study in selected patients would need to be performed to demonstrate clinical feasibility.

The vestibular and geniculate ganglia of the ear in experimental animals carry both of the tyrosine hydroxylase (TH)-positive sympathetic neurons and the neuronal nitric oxide synthase (nNOS)-positive parasympathetic neurons. With an aid of immunohistochemistry, we examined these ganglia as well as the horizontal part of the facial nerve using specimens from 10 formalin-fixed elderly cadavers. The submandibular ganglion from the same cadavers was used for the positive control for both markers. Although there was a nonspecific reaction in nuclei for the present antibody of nNOS, these ganglia were unlikely to contain either nNOS- or TH-positive neurons. However, we did not deny a possibility that the absence was a result of degeneration with aging. In contrast, the facial nerve horizontal part consistently contained both of TH-positive- and nNOS-positive fibers. These fibers might regulate blood supply to the facial nerve and the dysregulation leads to edema to elevate pressure on the nerve within its osseous canal.

It is established that neuropeptide Y (NPY) is a transmitter of parasympathetic secretory impulses in submandibular gland. The neuropeptides substance P, vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) are likely mediators of secretory parasympathetic responses of the gland. Previously, we have shown that substance P, VIP and CGRP modulate voltage-dependent Ca(2+) channels (VDCCs) in hamster submandibular ganglion (SMG) neurons. In this study, we attempt to characterize the effect of NPY on VDCCs current using Ba(2+) (I(Ba)) in SMG neurons. Application of NPY caused both facilitation and inhibition of L-type and N/P/Q-type I(Ba), respectively. Intracellular dialysis of the Gα(s)-protein antibody attenuated the NPY-induced facilitation of I(Ba). The adenylate cyclase (AC) inhibitor, as well as protein kinase A (PKA) inhibitor attenuated the NPY-induced facilitation of I(Ba). Intracellular dialysis of the Gα(i)-protein antibody attenuated the NPY-induced inhibition of I(Ba). Application of a strong depolarizing voltage prepulse attenuated the NPY-induced inhibition of I(Ba). These results indicate that NPY facilitates L-type VDCCs via Gα(s)-protein involving AC and PKA. On the other hand, NPY also inhibits N/P/Q-type VDCCs via Gα(i)-protein βγ subunits in the SMG neurons.

The cranial parasympathetic ganglia have been reported to paradoxically contain the sympathetic nerve marker, tyrosine hydroxylase (TH), in addition to neurons expressing parasympathetic markers such as vasoactive intestinal peptide (VIP) and neuronal nitric oxide synthase (nNOS). However, the distribution of these molecules in the cranial ganglia of human fetuses has not yet been examined. Using paraffin sections from 10 mid-term human fetuses (12-15 weeks), we performed immunohistochemistry for TH, VIP, and nNOS in the parasympathetic ciliary, pterygopalatine, otic, and submandibular ganglia, and for comparison, the sensory inferior vagal ganglion. The ciliary and submandibular ganglia contained abundant TH-positive neurons. In the former, TH-positive neurons were much more numerous than nNOS-positive neurons, whereas in the latter, nNOS immunoreactivity was extremely strong. No or a few cells in the pterygopalatine, otic, and inferior vagal ganglia expressed TH. Ciliary TH neurons appeared to compensate for classically described sympathetic fibers arising from the superior cervical ganglion, whereas in the submandibular ganglion, nNOS-positive neurons as well as TH neurons might innervate the lingual artery in addition to the salivary glands. Significant individual variations in the density of all these markers suggested differences in sensitivity to medicine affecting autonomic nerve function. Consequently, in the human cranial autonomic ganglia, it appears that there is no simple dichotomy between sympathetic and parasympathetic function.

Objective The control of saliva secretion is mainly under parasympathetic control. The submandibular ganglion (SMG) is a parasympathetic ganglion which receives inputs from preganglionic cholinergic neurons, and innervates the submandibular salivary gland to control saliva secretion. The aim of this study was to investigate if adrenomedullin (ADM) and/or calcitonin gene-related peptide (CGRP) modulate voltage-dependent calcium channel (VDCCs) current ( I Ca ) in SMG. Design The profile of CGRP and ADM actions in SMG was studied using the whole-cell configuration of the patch-clamp technique. Results Both ADM and CGRP facilitated I Ca . These facilitations were attenuated by intracellular dialysis of the anti-Gα s -protein and pretreatment of SQ22536 (an adenylate cyclase inhibitor). Conclusions ADM and CGRP facilitates VDCCs mediated by Gα s -protein and adenylate cyclase in SMG.

Although abnormal processing of amyloid precursor protein (APP) leads to early onset of Alzheimer's disease, the normal function of this protein is poorly understood. APP is widely expressed in axons, dendrites, and synapses in both central and peripheral nervous systems. Mice homozygous for APP or its homologue APP-like protein 2 (APLP2) null mutation (KO) are viable, but double mutants for APP and APLP2 deletions (DKO) are early postnatal lethal. To investigate the role of APP in synapse development, we compared the ultrastructure of submandibular ganglion synapses between DKO and littermate APLP2 KO mice at birth. Using serial electron microscopy, we found that the size of presynaptic boutons and the number of active zones per bouton were comparable in both strains of animals. However, the synaptic vesicle density, active zone size, and docked vesicle number per active zone were significantly reduced in DKO compared to those in APLP2 KO. These results indicate that the APP family of proteins plays an important role in regulating the formation and function of inter-neuronal synapses.

The control of saliva secretion is mainly under parasympathetic control, although there also could be a sympathetic component. Sympathetic nerves are held to have a limited action in secretion in submandibular glands because, on electrical stimulation, only a very small increase to the normal background, basal secretion occurs. Parasympathetic stimulation, on the other hand, caused a good flow of saliva with moderate secretion of acinar mucin, plus an extensive secretion of granules from the granular tubules. The submandibular ganglion (SMG) is a parasympathetic ganglion which receives inputs from preganglionic cholinergic neurons, and innervates the submandibular salivary gland to control saliva secretion. Neurotransmitters and neuropeptides acting via G-protein coupled receptors (GPCRs) change the electrical excitability of neurons. In these neurons, many neurotransmitters and neuropeptides modulate voltage-dependent calcium channels (VDCCs). The modulation is mediated by a family of GPCRs acting either directly through the membrane delimited G-proteins or through second messengers. However, the mechanism of modulation and the signal transduction pathway linked to an individual GPCRs depend on the animal species. This review reports how neurotransmitters and neuropeptides modulate VDCCs and how these modulatory actions are integrated in SMG systems. The action of neurotransmitters and neuropeptides on VDCCs may provide a mechanism for regulating SMG excitability and also provide a cellular mechanism of a variety of neuronal Ca(2+)-dependent processes.

703 e attempted to provide a framework to understand the normal anatomy and to outline the features of lesions in the submandibular space. Techniques In most cases, a high-resolution (7-12– MHz) linear transducer is useful, although a higher frequency (>12-MHz) transducer with a small contact surface area may be necessary in a smaller or angular region. The images were obtained mainly in an axial plane using a submandibular view with oblique or coronal High-Resolution Sonography of the Submandibular Space: Anatomy and Abnormalities A. S. C. Ching 1 and A. T. Ahuja 2

Angiotensin II (AngII) is one of the most important vasoconstrictive hormones but is also known to act as a neuromodulator and a neurotransmitter in the central and peripheral nervous systems. In a previous study, we have shown that AngII, mediated by AT 1 receptors, inhibits voltage-dependent calcium channel (VDCC) currents (I Ca ) via G-proteins in submandibular ganglion (SMG) neurons. In this study, we further characterized the signal transduction of AngII-induced inhibition of I Ca . Application of 1 μM AngII inhibited I Ca by 32.1±2.7% (mean±S.E.M., n =9). Intracellular dialysis of anti-G q/11 antibodies attenuated these inhibition (8.8±1.3%, n =6). In addition, treatment of protein kinase C (PKC) activator and inhibitor also attenuated these inhibition (8.0±0.9 and 9.8±0.9%, n =6 and 9, respectively). We therefore conclude that AngII inhibits VDCC via G q/11 -proteins involving in SMG neurons. In addition, such PKC-dependent pathways mediated mainly L-type VDCC inhibition.

In a previous study, we demonstrated that angiotensin II (Ang II) inhibited voltagedependent calcium channels (VDCCs) currents (ICa) in hamster submandibular ganglion (SMG) neurons. In sinoatrial node cells, it has been reported that Ang II inhibits ICa by suppressing cyclic AMP production. In this study, to investigate the possible involvement of a cyclic AMP-cyclic AMP dependent protein kinase (PKA) pathway in the Ang II-induced inhibition of ICa, effects of Ang II were examined in SMG neurons after treatment with an activator and inhibitor of PKA. Neither pretreatment of neurons with membrane permeable cyclic AMP nor intracellular dialysis of PKA blocker attenuated the Ang II-induced inhibition of ICa. These results indicate that Ang II inhibited ICa via a cyclic AMP-PKA-independent mechanism in SMG neurons.

Purpose Knowledge of lingual nerve anatomy is of paramount importance to dental practitioners and maxillofacial surgeons. The purpose of this article is to review lingual nerve anatomy from the cranial base to its insertion in the tongue and provide a more detailed explanation of its course to prevent procedural nerve injuries. Materials and Methods Fifteen human cadavers from the University of Alabama at Birmingham School of Medicine's Anatomical Donor Program were reviewed. The anatomic structures and landmarks were identified and confirmed by anatomists. Lingual nerve dissection was carried out and reviewed on 15 halved human cadaver skulls (total specimens, 28). Results Cadaveric dissection provides a detailed examination of the lingual nerve from the cranial base to tongue insertion. The lingual nerve receives the chorda tympani nerve approximately 1 cm below the bifurcation of the lingual and inferior alveolar nerves. The pathway of the lingual nerve is in contact with the periosteum of the mandible just behind the internal oblique ridge. The lingual nerve crosses the submandibular duct at the interproximal space between the mandibular first and second molars. The submandibular ganglion is suspended from the lingual nerve at the distal area of the second mandibular molar. Conclusion A zoning classification is another way to more accurately describe the lingual nerve based on close anatomic landmarks as seen in human cadaveric specimens. This system could identify particular areas of interest that might be at greater procedural risk.

Organs are complex structures composed of different kinds of cells and tissues that must develop in a coordinated manner. Although instructive signals from developing organs to the innervating neurons are well known, how innervating neurons contribute to the development of their targets is less studied. Nedvetsky et al . examined the development of the mouse submandibular salivary gland (SMG), which is innervated by parasympathetic nerves emanating from the parasympathetic submandibular ganglion (PSG). Previous work showed that acetylcholine released from the PSG neurons mediated the maintenance of a population of progenitor cells required for the development of full-sized SMG (see Houtz and Kuruvilla). Here, vasoactive intestinal peptide (VIP), another signaling molecule released from PSG neurons, was determined to play a role in SMG development. Ex vivo cultures of embryonic SMG, which include the innervating neurons, exposed to an inhibitor of the neurotrophic factor neurturin exhibited shortened nerves, impaired innervation, reduced epithelial branching, and impaired duct formation. Whereas inhibition of muscarinic acetylcholine signaling resulted in smaller SMGs with reduced epithelial branching, duct width and midline accumulation of duct precursors appeared unaffected. In contrast, inhibition of VIP signaling with a VIP receptor 1 (VIPR1) antagonist resulted in reduced epithelial branching with disrupted condensation of the ductal precursors at the midline and increased duct width. Exposure of PSG to neurturin stimulated the expression of the gene encoding VIP, and transcriptional microarray analysis showed that VIP expression increased at the time of secondary duct formation and lumenization. VIP was enriched in the PSG and absent from the SMG epithelia; VIPR1 was primarily present in the SMG epithelia. When cocultured with PSG in the presence of neurturin, rudimentary SMG epithelial cultures (lacking mesenchymal cells or nerves) exhibited increased branching and ductal length, the latter of which was blocked by inhibition of VIPR1 and was mimicked by exposing the cultures to VIP in the absence of PSG. Furthermore, culturing the rudimentary epithelia in the presence of VIP enabled the formation of a continuous ductal lumen, which was dependent on protein kinase A (PKA) activity; without VIP, the epithelia formed small, discontinuous microlumens. VIP stimulated the production of adenosine 3′,5′-monophosphate (cAMP) and phosphorylation of a PKA target in the rudimentary epithelial cultures, and pharmacological analysis with specific agonists or antagonists of cAMP effectors showed that PKA was important for ductal elongation in the rudimentary epithelial cultures and for lumen formation in the ex vivo cultured SMG. Fluid flow can stimulate lumen expansion, and the Cl – -conducting cystic fibrosis transmembrane conductance regulator (CFTR) stimulates fluid flow and is activated by VIP. Inhibition of CFTR blocked VIP-induced lumen expansion in the epithelial cultures. In vivo inhibition of VIPR1 during the period of SMG development resulted in narrower lumen, and CFTR -null mice had SMGs with abnormal duct morphology. Thus, this provides another example showing that signaling in both directions, from the tissue to the nerves and from the nerves to the tissue, is needed for proper organogenesis. P. I. Nedvetsky, E. Emmerson, J. K. Finley, A. Ettinger, N. Cruz-Pacheco, J. Prochazka, C. L. Haddox, E. Northrup, C. Hodges, K. E. Mostov, M. P. Hoffman, S. M. Knox, Parasympathetic innervation regulates tubulogenesis in the developing salivary gland. Dev. Cell 30 , 449–462 (2014). [PubMed] J. Houtz, R. Kuruvilla, VIP pipes up: Neuronal signals direct tubulogenesis. Dev. Cell 30 , 361–362 (2014). [PubMed]

The calcium ion influx through voltage-dependent calcium channels (VDCCs) has a vital role in the control of neurotransmitter release and membrane excitability. The modulation of VDCCs controls the extent of calcium entry and thus provides a way of regulating neuronal function. Prepulse facilitation is a phenomenon in which a strong depolarizing pulse induces a form of the VDCCs that exhibits an increased opening probability in response to a given test potential that persists for several seconds after repolarization. In this study, we have studied the characterization of prepulse facilitation of VDCCs currents (Ica) in hamster submandibular ganglion (SMG) neurons, using whole-cell patch clamp recordings. In SMG neurons, application of a strong depolarizing prepulse caused a Ica. In 8 SMG neurons, rate of facilitation was 1.1 +/- 0.1. The greatest value of prepulse facilitation was obtained with prepulse to +100 mV, 10 ms duration in this neuron. The magnitude of facilitation was dependent on changing the interval between the -prepulse and the +prepulse and reached a maximum at a interval of 500 ms.

Neurturin (NRTN), signalling via the GDNF family receptor alpha2 (GFRalpha2) and Ret tyrosine kinase, has recently been identified as an essential target-derived factor for many parasympathetic neurons. NRTN is expressed in salivary and lacrimal glands, while GFRalpha2 and Ret are expressed in the corresponding submandibular, otic and sphenopalatine ganglia. Here, we have characterized in more detail the role of GDNF and NRTN signalling in the development of cranial parasympathetic neurons and their target innervation. Gfra1 mRNA was expressed at E12 but not in newborn cranial parasympathetic ganglia, while Gfra2 mRNA and protein were strongly expressed in newborn and adult cranial parasympathetic neurons and their projections, respectively. In newborn GFRalpha1- or Ret-deficient mice, where many submandibular ganglion neurons were still present, the otic and sphenopalatine ganglia were completely missing. In contrast, in newborn GFRalpha2-deficient mice, most neurons in all these ganglia were present. In these mice, the loss and atrophy of the submandibular and otic neurons were amplified postnatally, accompanied by complete loss of innervation in some target regions and preservation in others. Surprisingly, GFRalpha2-deficient sphenopalatine neurons, whose targets were completely uninnervated, were not reduced in number and only slightly atrophied. Thus, GDNF signalling via GFRalpha1/Ret is essential in the early gangliogenesis of some, but not all, cranial parasympathetic neurons, whereas NRTN signalling through GFRalpha2/Ret is essential for the development and maintenance of parasympathetic target innervation. These results indicate that GDNF and NRTN have distinct functions in developing parasympathetic neurons, and suggest heterogeneity among and within different parasympathetic ganglia.

The distribution of neuronal-constitutive nitric oxide synthase (ncNOs)-positive nerve fibres was compared immunohistochemically, and the effect of NOs inhibitor and NO scavenger on the secretory response was compared functionally, in the two glands. Numerous ncNOs-positive fibres were distributed around acini in the submandibular gland but scarcely any around acini in the sublingual gland. Within the submandibular ganglion (parasympathetic), the nerve-cell bodies were strongly positive. Within the superior cervical ganglion (sympathetic), the nerve-cell bodies were negative, although some positive nerve fibres were observed. The secretory responses to the electrical stimulation of the chorda were significantly reduced by the NOs inhibitor, NG-nitro- l -arginine methyl ester (L-NAME, 10−9–10−3 M) in a dose-dependent manner. The NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO) also reduced the chorda-evoked secretion (10−9–10−6 M). The submandibular secretions evoked by stimulation of the superior cervical ganglion were not affected by L-NAME or carboxy-PTIO. In the sublingual gland, neither L-NAME nor carboxy-PTIO affected chorda-evoked salivary secretion. The histochemical and functional results both suggest that NO plays an excitatory role in the regulation of parasympathetic nerve-induced salivary secretion in the rat submandibular gland, but not in the sublingual gland.

Both substance P and neurokinin A are known as neurotransmitters of the submandibular ganglion cell. In this study, the effects of neurokinin (NK) receptor-subtype agonists on hamster submandibular ganglion cells were investigated using the whole-cell patch-clamp technique. Membrane currents evoked by a ramp pulse from +50 to −100 mV (−150 mV/1000 msec) were compared in both the absence and presence of NK receptor agonist. The NK-1 receptor agonist [Sar 9 , Met (O 2 ) 11 ]-substance P, the NK-2 receptor agonist [Ala 5 , β-Ala 8 ]-α-neurokinin fragment 4–10, and the NK-3 receptor agonist senktide were used. The three agonists dose-dependently increased the amplitude of the inward current with a reversal potential near 0 mV. Their rank order was NK-1=NK-3>NK-2. Even when the external solution was replaced with Cs + or N -methyl- d -glucamine + instead of Na + , the NK receptor agonists also increased the amplitude of the inward current. Thus, NK-1 and NK-3 receptors are apparently coupled with non-selective cation channels in submandibular ganglion cells.