[Topographic features of lingual nerve and its relationship with other anatomical structures in maxillolingual groove]

By surgical interventions in maxillolingual groove area one should consider anatomical variations and topography of vessels, glands ducts and lingual nerve to prevent their injury. At the Department of Operative Surgery and Topographic Anatomy of the First Moscow State Medical University named after I.M. Sechenov we carried out anatomical study on cadavers (men and women, n=30).The study revealed topographical features of the lingual nerve and its relationship to other anatomical structures in the maxillolingual groove. It was found out that at the level of the second molar (96%) lingual nerve "crosses" duct of submandibular salivary gland, at the level of the third molar lingual nerve is located under the duct and lateral to it, closer to the inner surface of the body of the mandible. At the level of the first molar lingual nerve is located above and medial to Wharton duct and passes along sublingual-lingual muscles (m.hyoglossus).

Sympathetic reinnervation of peripheral targets following bilateral axotomy of the adult superior cervical ganglion

The ability of adult injured postganglionic axons to reinnervate cerebrovascular targets is unknown, yet these axons can influence cerebral blood flow, particularly during REM sleep. The objective of the present study was to assess quantitatively the sympathetic reinnervation of vascular as well as non-vascular targets following bilateral axotomy of the superior cervical ganglion (SCG) at short term (1 day, 7 day) and long term (8 weeks, 12 weeks) survival time points. The sympathetic innervation of representative extracerebral blood vessels [internal carotid artery (ICA), basilar artery (BA), middle cerebral artery (MCA)], the submandibular gland (SMG), and pineal gland was quantified following injury using an antibody to tyrosine hydroxylase (TH). Changes in TH innervation were related to TH protein content in the SCG. At 7 day following bilateral SCG axotomy, all targets were significantly depleted of TH innervation, and the exact site on the BA where SCG input was lost could be discerned. Complete sympathetic reinnervation of the ICA was observed at long term survival times, yet TH innervation of other vascular targets showed significant decreases even at 12 weeks following axotomy. The SMG was fully reinnervated by 12 weeks, yet TH innervation of the pineal gland remained significantly decreased. TH protein in the SCG was significantly decreased at both short term and long term time points and showed little evidence of recovery. Our data demonstrate a slow reinnervation of most vascular targets following axotomy of the SCG with only minimal recovery of TH protein in the SCG at 12 weeks following injury.

Botox(®) to reduce drooling in a paediatric population with neurological impairments: a Phase I study

BACKGROUND

The treatment of drooling in a paediatric population with neurological impairments is clinically challenging. Surgery is considered invasive, while behaviour modification techniques, correction of situational factors and oral-motor therapy do not always produce sustained improvement. In recent years the use of Botox® to decrease drooling has been investigated.

AIMS

To review the clinical data from a Drooling Treatment Project for children with neurological impairments and to establish the validity of the drooling severity and frequency rating scales, establishing Phase I-level information about the therapeutic use of submandibular salivary gland injections of Botox® in various contexts.

METHOD & PROCEDURES

A retrospective, explanatory design was used to review the data. Nine children, seven with cerebral palsy and two with operculum syndrome, ranging in age from 5 to 17 years (mean = 9;3 years) were included. Drooling was assessed by qualified speech-language therapists using drooling rating scales, in five different situations and at different time points pre- and post-Botox® injection up to 6 months. Quantitative and qualitative analyses were computed. Parents'/primary caregivers' perceptions of drooling and treatment with Botox® were also considered using an interview form and a quality of life questionnaire.

OUTCOMES & RESULTS

Statistically significant reductions in drooling with large effect sizes were obtained in the communicating and general appearance situations. There was a difference in the pattern of response between the children with cerebral palsy and those with operculum syndrome. Discrepancies between the parents and the speech-language therapists regarding the context of drooling reduction were found. Most parents/primary caregivers felt their children's lives and their own had improved following the Botox® injection and would repeat the treatment. The drooling rating scales were a valid method to assess drooling in a clinical situation.

CONCLUSIONS & IMPLICATIONS

In the clinical setting of the Drooling Treatment Project, the results indicated that the context in which drooling occurs is an important factor and suggested the value of considering the situational context when making drooling judgments. Further, there was a difference in the pattern of response between the children with cerebral palsy and those with operculum syndrome, suggesting that aetiology may be involved in the response to Botox®.

The changes in submandibular gland size and function following chorda tympani section

To investigate the effects of chorda tympani section on submandibular gland size and function in the early (postoperative day 7) and late (postoperative month 6) postoperative period by ultrasonography, scintigraphy, and biochemical analysis of the saliva patients with unilateral chronic otitis media. One-hundred and thirty patients (46 males and 84 females) who were ≥16 years of age and diagnosed with unilateral chronic otitis media and for whom type 1 tympanoplasty was indicated in 1st Outpatient Clinic of Kartal Dr. Lutfi Kirdar Training and Research Hospital between August 2004 and February 2007 were enrolled in the study. Of 130 patients, 102 patients who were eligible and gave written approval were included in the study. However, of these patients 99 underwent type 1 tympanoplasty and 3 had a canal down mastoidectomy. In 99 patients, chorda tympani nerves of 16 were cut, but 3 patients had to be excluded due to allergic reactions. Before the operation, bilateral submandibular gland ultrasonography was performed on all patients and the anterior-posterior length, the frontal lateral-medial width (transverse), and the paramandibular depth of both submandibular glands were measured. In scintigraphic examinations, perfusion index (PI), uptake ratio and excretion fraction were measured. Then, in biochemical analysis of the saliva the levels of sodium, potassium, chloride, calcium, magnesium, amylase, and the values of pH and density were assessed by the saliva collection through Wharton duct. In the statistical comparison of operated and healthy side of the patients with respect to these parameters Mann-Whitney U test, and in intragroup analysis Wilcoxon test was used. The volume of the submandibular gland of the operated side was significantly lower compared to the healthy side in postoperative month 6 (P < 0.05). According to the baseline volume of the submandibular gland of the healthy side, the increase in postoperative day 7 and month 6 were found to be statistically insignificant (P > 0.05). According to the baseline PI value, the decreases in the PI value in the postoperative day 7 and postoperative month 6 were statistically significant (P < 0.01). The uptake ratio of the patients was lower in the postoperative day 7 and month 6 than those at the baseline; however, the difference was statistically insignificant (P > 0.05). The excretion fraction values in the postoperative day 7 were significantly lower than the baseline values (P < 0.05), whereas the decrease in the EF values in the postoperative month 6 were statistically insignificant (P > 0.05). In conclusion, the present study was the first in the literature in which three parameters of assessment, such as ultrasonography, scintigraphy, and biochemical analysis, were used to determine the changes in submandibular gland size and function following the chorda tympani section. After chorda tympani section, the volume of submandibular gland decreased in the late postoperative period. Moreover, chorda tympani section led to decrease in the saliva secretion and the PI value of the patients in the early and late postoperative period.

Parasympathetic innervation maintains epithelial progenitor cells during salivary organogenesis

The maintenance of a progenitor cell population as a reservoir of undifferentiated cells is required for organ development and regeneration. However, the mechanisms by which epithelial progenitor cells are maintained during organogenesis are poorly understood. We report that removal of the parasympathetic ganglion in mouse explant organ culture decreased the number and morphogenesis of keratin 5-positive epithelial progenitor cells. These effects were rescued with an acetylcholine analog. We demonstrate that acetylcholine signaling, via the muscarinic M1 receptor and epidermal growth factor receptor, increased epithelial morphogenesis and proliferation of the keratin 5-positive progenitor cells. Parasympathetic innervation maintained the epithelial progenitor cell population in an undifferentiated state, which was required for organogenesis. This mechanism for epithelial progenitor cell maintenance may be targeted for organ repair or regeneration.

[Effect of botulinum toxin-A on secretion of parasympathetic denervated rabbit submandibular gland]

OBJECTIVE

To investigate the effect of botulinum toxin-A (BTX-A) on secretion of parasympathetic denervated rabbit submandibular gland.

METHODS

Twenty-four rabbits were divided into 3 groups: control (n = 4), parasympathetic denervated submandibular gland (n = 4), and parasympathetic denervated submandibular gland with 5 U BTX-A injection (n = 16). Secretion flow was measured by Schirmer test. Composition of saliva was detected by biochemical method.

RESULTS

Secretion of parasympathetic denervated submandibular gland increased by 139.0% in rest time (P < 0.01), but decreased by 64.2% in feeding time (P < 0.01) compared with controls. Secretion of submandibular gland decreased in rest time 1, 2, 4, and 12 weeks after BTX-A injection compared with that of parasympathetic denervated submandibular gland without injection (P < 0.05), which was also the same in feeding time 1 and 2 week after injection (P < 0.05). The concentrations of amylase, sodium, potassium, chloride and protein of saliva were not changed after BTX-A injection.

CONCLUSIONS

BTX-A could decrease the secretion of parasympathetic denervated submandibular gland.

Components of the NGF signaling complex are altered in mdx mouse superior cervical ganglion and its target organs

We previously reported that in the superior cervical ganglion (SCG) of dystrophic mdx mice, which lack full-length dystrophin, there is a loss of neurons projecting to SCG muscular targets, like the iris. Nonetheless, surviving neurons, innervating either iris or submandibular gland (SuGl), a SCG non-muscular target, underwent reduced axon defasciculation and terminal branching. Here we report that, during early post-natal development, levels of pro-apoptotic proNGF in mdx mouse iris, but not in the SuGl, are higher than in the wild-type. This increase, along with reduced levels of NGF receptors (TrkA and p75NTR) in SCG, may be partly responsible for the observed loss of neurons projecting to the iris. These alterations, combined with a reduction in polysialylated-NCAM and neurofilament protein levels in SCG, may also account for reduced axon defasciculation and terminal branching in mdx mouse SCG targets.

Peripheral projections of NESP55 containing neurons in the rat sympathetic ganglia

The peripheral projections of neurons expressing neuroendocrine secretory protein 55 (NESP55), a novel member of the chromogranin family, were studied by retrograde tracing technique. It was found that NESP55 positive neurons in the rat superior cervical ganglion projected to a number of targets including the submandibular gland, the cervical lymph nodes, the forehead skin, the iris, but not to the thyroid. Among these NESP55 positive target-projecting neurons, a subpopulation contained neuropeptide Y (NPY), a vasoconstrictor. Forepaw pad projecting neurons were found exclusively in the stellate ganglion, almost all of which (approximately 90%) were immunoreactive to NESP55. Colocalization of NESP55 and calcitonin gene-related peptide (CGRP), a peptide involved in sudomotor effects, was observed in a subpopulation of these paw pad projecting neurons, as was colocalization of NESP55 and NPY. The data suggest that NESP55 may have a functional role in some populations of sympathetic neurons.

Studies on the control of mucin production

The process of synthesizing a mucin molecule is discussed, primarily from the standpoint of glycoconjugate biosynthesis. The control of the activation steps in the making of nucleotide sugars is detailed, stressing the molecular mechanisms operating. These include: supply of glycolytic intermediates; the pyridine nucleotide redox potential; the energy state as expressed in nucleotide potential; and feedback modifiers. Next, the glycosyl transferases are discussed, as are suggestions of control at the first committment step and the subjects of specificity of donor and acceptor molecules and the associational state of the glycosyl transferases. The secondpart of the paper describes a model system in vivo. The paired cat submandibular glands are exposed and, in one, blood supply and salivary duct are cannulated and the parasympathetic and sympathetic nerve exposed. This preparation uses the contralateral gland as control and enables certain questions to be asked: 1. Does the cell produce incomplete mucins when the biosynthetic rate is high? 2. Does the energy state of the cell 'keep up with' the high rates of synthesis? 3. What is the extent of post-synthetic modifications? 4. What cell types are involved in mucin elicited by different chemical or electrical stimuli? 5. What is the time involved in synthesis and storage?

Intraglandular application of botulinum toxin leads to structural and functional changes in rat acinar cells

BACKGROUND AND PURPOSE

Intraglandular injection of botulinum toxin (BoNT) leads to a transient denervation of the submandibular gland and this is associated with reduced salivary secretion. The purpose of the present study was to verify whether temporary acinar atrophy occurs simultaneously with chemical denervation of the glands.

EXPERIMENTAL APPROACH

Tissue specimens of the right submandibular gland taken from 18 Wistar rats after intraglandular injection of BoNT A, BoNT B, or a combination of both were examined. As a sham control, an equivalent volume of saline was injected into the left submandibular gland. Morphometric measurements, immunohistochemistry, electron microscopy and western blot analysis were used to analyse the morphological and functional changes of the denervated glands.

KEY RESULTS

Morphological and ultrastructural analyses of the cell organelles and secretory granula showed a clear atrophy of the acini, which was more prominent in glands injected with the combination of BoNT/A and B. Morphometric measurements of the glandular acini revealed a significant reduction of the area of the acinar cells after injection of BoNT (P=0.031). The expression of amylase was significantly reduced in BoNT treated glands.

CONCLUSIONS AND IMPLICATIONS

Intraglandular application of BoNT induces structural and functional changes of the salivary glands indicated by glandular atrophy. These effects may be due to glandular denervation induced by the inhibition of the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors (SNAREs) involved in acetylcholine release at the neuroglandular junction and also specially inhibition of those involved in exocytosis of the granula of the acinar cells.

Acetylcholine synthesis, muscarinic receptor subtypes, neuropeptides and secretion of ferret salivary glands with special reference to the zygomatic gland

Studies on salivary secretion are usually focused on parotid and submandibular glands. However, the film of mucin, that protects the oral structures and is responsible for the feeling of oral comfort, is produced by the submucosal glands. The submucosal zygomatic and molar glands are particularly large in carnivores such as the ferret. Comparisons between the mucous sublingual, zygomatic and molar glands, serous parotid and sero-mucous submandibular glands showed the acetylcholine synthesis, in terms of concentration, to be three to four times higher in the mucous glands than in the parotid and submandibular glands. Bromoacetylcholine inhibited 95-99% of the synthesis of acetylcholine in the incubates of the five types of glands, showing the acetylcholine synthesis to depend on the activity of choline acetyltransferase. The high acetylcholine synthesis in the zygomatic gland was of nervous origin, since cutting the buccal nerve, aiming at parasympathetic denervation, and allowing time for nerve degeneration, reduced the acetylcholine synthesising capacity of the gland by 95%. A similar reduction (96%) in the parotid gland followed upon the avulsion of the parasympathetic auriculo-temporal nerve. Zygomatic saliva was very viscous. The salivary flow rate in response to electrical stimulation (20 Hz) of the buccal nerve (zygomatic gland), expressed per gland weight, was one-third of that to stimulation of the auriculo-temporal nerve (parotid gland) or the chorda-lingual nerve (submandibular gland). As previously shown for the parotid and submandibular gland, a certain fraction (25%) of the parasympathetic secretory response of the zygomatic gland depended on non-adrenergic, non-cholinergic transmission mechanisms, probably involving substance P and vasoactive intestinal peptide and possibly calcitonin gene-related peptide. Particularly, high concentrations of vasoactive intestinal peptide were found in the sublingual and molar glands, and of substance P in the submandibular, zygomatic and molar glands; notably, the concentration of calcitonin gene-related peptide of the sublingual gland was not detectable. All five muscarinic receptor subtypes were detected in the five glands. The receptor protein profile, as judged by immunoblotting and semi-quantitative estimations, was about the same in the glands: high level of M3, low level of M2 and levels roughly in the same range of M1, M4 and M5. Compared to the parotid and submandibular glands, the M5 receptor level was particularly low in the mucin-secreting glands. The present study points out both similarities and dissimilarities between the five types of glands investigated. The zygomatic gland, in particular, appears to be a suitable model for future studies aiming at causing relief of dry mouth by local pharmacological treatment.

Transcervical Submandibular Sialoadenectomy

The submandibular glands are subject to several pathologies that require excision. The most common problem that affects these salivary glands is sialadenitis combined with sialolithiasis. This problem occurs in the submandibular gland 10 times more frequently than it does in the parotid gland. Other illnesses frequently involving the submandibular glands are represented by sialadenosis and benign, malign, and intermediate neoplasms. Diagnosis of any disturbance in the submandibular gland involves both a clinical and instrumental (echography, traditional radiography [ortopantomography] and eventually computed tomography (CT) or magnetic resonance imaging) assessment. Surgery is the usual method of treatment of both chronic sialadenitis and neoplasms in the submandibular gland. A submandibular gland surgical approach can be cervical, intraoral, or endoscopic. The authors present their clinical experience with a total of 40 patients with illnesses involving the submandibular gland treated with submandibular gland excision by a transcervical approach. Their experience suggests that this approach entails a relatively simple procedure, involves low risks for the nerve structure around the gland, permits wide resection margins for neoplasms, and incurs little aesthetic damage.

Saliva Secretion Stimulated by Grafted Nerve in Submandibular Gland Allograft in Dogs

BACKGROUND

Recent studies have described submandibular gland allografts in animal models; however, the amount of saliva secretion or nervous regeneration in those animals have not been reported. Herein, we investigated saliva secretion from submandibular gland allografts in beagle dogs.

METHODS

Using a vascularized submandibular gland transplantation method, we extracted portions of the submandibular gland including the duct from beagle dogs and placed them into the submental region of age- and weight-matched dogs. Differences in the amount of saliva secretion and histologic appearance were compared based on the existence of chorda tympani branches in the allograft.

RESULTS

At 10 weeks after transplantation, the amount of resting saliva in the group grafted with the nerve was clearly increased, whereas the quantity of that in the group that underwent transplantation without the nerve was quite low. In the former group, responses were demonstrated after taste stimulation and electronic nerve stimulation.

CONCLUSIONS

Our results showed a clear relationship between the presence of a nerve in grafted submandibular glands and saliva secretion.

Rat salivary gland ligation causes reversible secretory hypofunction

AIM

To determine the influence of inflammation on salivary secretion. Secretion by salivary glands involves interactions between nerves, blood vessels and salivary cells. The present study investigated the effects of inflammation on rat submandibular gland function following acute ductal obstruction.

METHODS

Under recovery anaesthesia a metal clip was placed on the main duct of the submandibular gland. After 24 h salivary secretion was evoked by nerve and methacholine stimulation. For recovery experiments the clip was removed after 24 h and the animal left to recover for 3 days when salivary function was again assessed.

RESULTS

By 24 h of obstruction an inflammatory infiltrate had developed within the obstructed gland and stimulated salivary flows were just 20% of the normal secretion, whilst protein secretion and ion reabsorption were also severely impaired. If ductal obstruction was removed after 24 h the salivary function returned to normal after 3 days of recovery. In vitro analysis of cells from 24-h ligated glands revealed normal changes in intracellular calcium (the main secondary messenger involved in fluid secretion) in response to methacholine stimulation. Protein secretion from isolated cells indicated some changes in particular to methacholine-induced protein secretion although a significant protein secretion was still seen in response to isoprenaline - the main stimulus for protein secretion.

CONCLUSION

This report demonstrates reversible salivary inhibition associated with an inflammatory infiltrate within the salivary gland.

Different subcellular distributions of the vesicular monoamine transporter, VMAT2, in subclasses of sympathetic neurons

A subpopulation of neurons in the rat superior cervical ganglion (SCG) was found to lack immunostaining for VMAT2, an isoform of the vesicular monoamine transporter that loads catecholamines into vesicles for release at the synapse. Double labeling with neuropeptide Y (NPY), a marker for vasomotor neurons, revealed selective cellular colocalization of NPY together with intense perinuclear staining for VMAT2. This implied that VMAT2-negative neurons were likely to have secretomotor and pilomotor phenotypes. We tested this by identifying peripheral noradrenergic axons by their expression of immunoreactivity for tyrosine hydroxylase (TH) and determining whether they also expressed NPY and VMAT2. This analysis revealed the presence of VMAT2-positive, non-vasomotor sympathetic axons in the submandibular gland and at the base of piloerector hairs. Together the results confirm earlier indications that virtually all sympathetic neurons in the rat SCG express VMAT2 and they show for the first time that functional subclasses of cells can be distinguished by different somatic levels of immunoreactivity for VMAT2.

Effects of isoflurane on parasympathetic vasodilatation in the rat submandibular gland

Volatile anesthetics have been known to suppress parasympathetic reflex vasodilatation in the lower lip and palate. However, in the submandibular gland, little is known about the effects of these anesthetics on the parasympathetic vasodilatation elicited by reflex and direct (i.e., non-reflex) activation of the parasympathetic vasodilator mechanisms. Although both parasympathetic vasodilatations were inhibited by isoflurane in a concentration- and time-dependent manner, the effects of continuous administration of the alpha(1)-adrenoceptor agonist methoxamine were markedly different: The reflex vasodilatation was not affected by methoxamine, while the direct vasodilatation was significantly reduced. Picrotoxin (GABA(A) receptor antagonist) attenuated the inhibitory effect of isoflurane on direct vasodilatation and the systemic arterial blood pressure. These findings suggest that the isoflurane-induced inhibitory effects on direct vasodilatation are produced by a decrease of peripheral vascular tone by GABAergic mechanisms, whereas those on the reflex vasodilatation are produced exclusively by the inhibition of the reflex center.

Endoscope-assisted submandibular sialoadenectomy: a pilot study

PURPOSE

To describe an endoscopic technique for submandibular sialoadenectomy in humans, as well as the equipment, instrumentation, and pertinent anatomy.

MATERIALS AND METHODS

Six submandibular sialoadenectomies were carried out in 5 patients (3 women, 2 men; mean age, 26.6 years; range, 16 to 42 years) via a 15 to 20 mm neck incision for insertion of the endoscopic camera and surgical instruments.

RESULTS

All operations were successful without conversion to an open surgery. Operative time was 20 to 120 minutes (mean, 65 minutes). All patients were discharged the day after surgery. There were no postoperative complications (hematoma, nerve injury, infection). All patients experienced a mild degree of edema, which had resolved totally at the 6-month follow-up visit. All patients were satisfied with the outcome and especially the cosmetic result.

CONCLUSIONS

Absence of extensive scars, nontraumatic dissection, and magnification of anatomic structures are the most obvious advantages of this innovative technique.

Vasodilatation in the submaxillary gland of the rabbit

1. In the rabbit, in contrast to the cat and dog, the vasodilatation and the secretion in the submaxillary gland which accompany parasympathetic nerve stimulation are correspondingly sensitive to atropine block. 2. It is concluded that true vasodilator nerve fibres to the submaxillary gland exist in the chorda tympani nerve of the rabbit. 3. The vasodilatation which follows sympathetic vasoconstriction in the submaxillary gland of the rabbit is small and variable. The possibility that this after-dilatation is due to an adrenergic neurotransmitter agent acting on beta-vascular receptors is discussed.

Distribution and function of muscarinic receptor subtypes in the ovine submandibular gland

The effects of muscarinic receptor antagonists on responses to electrical stimulation of the chorda-lingual nerve were determined in pentobarbitone-anesthetized sheep and correlated to the morphology of tissue specimens. Stimulation at 2 Hz continuously, or in bursts of 1 s at 20 Hz every 10 s, for 10 min induced similar submandibular fluid responses (19 ± 3 vs. 21 ± 3 μl·min−1·g gland−1), whereas vasodilatation was greater during stimulation in bursts (−52 ± 4 vs. −43 ± 5%; P < 0.01). Continuous stimulation at 8 Hz induced substantially greater responses (66 ± 9 μl·min−1·g gland−1 and −77 ± 3%). While atropine (0.5 mg/kg iv) abolished the secretory response at 2 and 20 Hz (1:10 s), a small response persisted at 8 Hz (<5%). The “M1-selective” antagonist pirenzepine (40 μg/kg iv) reduced the fluid response at all frequencies tested ( P < 0.05–0.01), most conspicuously at 2 Hz (reduced by 69%). Methoctramine (“M2/M4-selective”; 100 μg/kg iv; n = 5) had no effect on fluid or the vascular responses but increased the protein output at 2 (+90%, P < 0.05) and 8 Hz (+45%, P < 0.05). The immunoblotting showed distinct bands for muscarinic M1, M3, M4, and M5 receptors, and immunohistochemistry showed muscarinic M1 and M3 receptors to occur in the parenchyma. Thus muscarinic M1 receptors contribute to the secretory response to parasympathetic stimulation but have little effect on the vasodilatation in the ovine submandibular gland. Increased transmitter release caused by blockade of neuronal inhibitory receptors of the M4 subtype would explain the increase in protein output.

Intraoral duct ligation without inclusion of the parasympathetic nerve supply induces rat submandibular gland atrophy

The atrophic effect of ligating the main duct of the right submandibular gland was examined in rat using a novel intraoral approach that did not include the chorda lingual (CL) nerve. Comparison was made with the effect of duct ligation including the attached CL nerve as carried out in previous studies. In all animals, the contralateral, unligated left submandibular gland was used as a control. At different times (1, 2, 7, 14 and 21 days) after ligation, glands were removed and weighed. Tissue was fixed for morphological analysis and homogenized for biochemical assay of secretory proteins. After 21 days, ligated glands showed a significant decrease in wet weight compared with unligated glands. Weight loss was the greatest (P < 0.05) in glands ligated with the CL nerve included. Light microscopy revealed that following ligation, an initial inflammatory reaction was followed by severe atrophy of acini and granular ducts. The atrophy was less severe when the CL nerve was not ligated. Secretory proteins were decreased from day 1 onwards following duct ligation in both groups. It can be concluded that most of the atrophy induced by duct ligation is independent of damage caused to the parasympathetic nerve supply, although the latter causes a greater atrophy presumably due to denervation.

Effects of ATP and GTP on voltage-gated K+ currents in glandular and muscular sympathetic neurons

This study assesses the effects of ATP and GTP on the kinetic properties of voltage-gated K+ currents in anatomically identified postganglionic sympathetic neurons innervating the submandibular gland and the masseter muscle in rats. Three types of K+ currents were isolated: the I(Af) steady-state inactivating at more hyperpolarized potentials, I(As) steady-state inactivating at less hyperpolarized potentials than I(Af) and the I(K) current independent of membrane potential. The kinetic properties of these currents were tested in neurons with ATP (4 mM) and GTP (0.5 mM) or without ATP and GTP in the intracellular solution. In glandular and muscular neurons in the absence of ATP and GTP in the intracellular solution, the current density of I(Af) was significantly larger (142 pA/pF and 166 pA/pF, respectively) comparing to cells with ATP and GTP (96 pA/pF and 100 pA/pF, respectively). The I(As) was larger only in glandular neurons (52 pA/pF vs. 37 pA/pF).Conversely, I(K) current density was smaller in glandular and muscular neurons without ATP and GTP (17 pA/pF and 31 pA/pF, respectively) comparing to cells with ATP and GTP (57 pA/pF and 58 pA/pF, respectively). In glandular (15.5 nA/ms vs. 6.9 nA/ms) and muscular (10.9 nA/ms vs. 7.5 nA/ms) neurons, the I(Af) activated faster in the absence of ATP and GTP. Half inactivation voltage of I(Af) in glandular (-110.0 mV vs. -119.7 mV) and muscular (-108.4 vs. -117.3 mV) neurons was shifted towards depolarization in the absence of ATP and GTP. We suggest that the kinetic properties of K+ currents in glandular and muscular sympathetic neurons change markedly in the absence of ATP and GTP in the cytoplasm. Effectiveness of steady-state inactivated currents (I(Af) and I(AS)) increased, while effectiveness of steady-state noninactivated currents decreased in the absence of ATP and GTP. The effects were more pronounced in glandular than in muscular neurons.

Microvascular transplantation and replantation of the dog submandibular gland

Transplantation and replantation of the submandibular gland with microvascular techniques were demonstrated in a previous study, with good gland survival. The application of radiation on the neck bed was attempted to address an actual clinical scenario in this study. Five canine submandibular glands were transplanted using microvascular techniques to the ipsilateral femoral system. Radiotherapy at a dosage level of 3,600 cGy using 600 cGy q.d was delivered to the nasopharyngeal and neck regions 2 weeks after transplantation. The transferred glands were then reintroduced into the original but radiated neck bed. The glands were harvested for histological examination 8 weeks later. Four of five canine submandibular glands can withstand microvascular transplantation and then replantation into a radiated neck bed for at least 8 weeks. However, the salivary function was depleted. The canine submandibular gland can survive the transplantation and replantation for at least 8 weeks in spite of precipitating radiation insult on the neck bed for 3 weeks. Neurorraphy is, however, essential to maintaining the glandular function.

The origin of sensory nerve fibers that innervate the submandibular salivary gland in the rat

The origin of sensory nerves that innervate the submandibular salivary gland was investigated in the rat. After application of wheat germ agglutinin-horseradish peroxidase to the cut endings of the sympathetic and parasympathetic nerve branches at the hilus of the gland, labeled cells were mainly found in the dorsal root ganglia and the trigeminal ganglion, respectively. The labeled neurons in these ganglia were of various sizes compared to unlabeled neurons, suggesting that the sensory nerves of the gland conduct various modalities of sensory information.

The influences of p75 neurotrophin receptor and brain-derived neurotrophic factor in the sympathetic innervation of target tissues during murine postnatal development

Post-ganglionic sympathetic neurons express the p75 neurotrophin receptor (p75NTR) and brain-derived neurotrophic factor (BDNF), which together have been implicated in controlling the degree of efferent innervation of peripheral organs [Kohn, J., Aloyz, R.S., Toma, J.G., Haak-Frendscho, M., Miller, F.D. 1999. Functionally Antagonistic Interactions between the TrkA and p75 Neurotrophin Receptors Regulate Sympathetic Neuron Growth and Target Innervation. J. Neurosci. 19, 5393-5408]. To examine this concept further, we developed null mutant mice lacking both p75NTR and BDNF, and assessed whether the loss of this receptor-ligand interaction negatively impacts the degree of sympathetic innervation to various target tissues. Between postnatal days 10 and 14, hearts, urinary bladders, kidneys, and submandibular salivary glands were isolated from p75(-/-)/BDNF-/-, p75-/-, BDNF-/-, and wild type siblings. Sympathetic axons were visualized using tyrosine hydroxylase (TH) immunohistochemistry, and TH protein levels were quantified by immunoblotting. Concerning the sympathetic innervation of the heart, urinary bladder and kidneys, no differences were seen in single and double null mutant mice, as compared with their wild type siblings. Sympathetic innervation of the submandibular salivary gland was, however, increased in both p75-/- and p75(-/-)/BDNF-/- mice over control mice. These results reveal that an absence of p75NTR and/or BDNF expression does not perturb the degree of sympathetic innervation of many peripheral tissues during postnatal development, and that a lack of p75NTR expression may actually enhance the density of these efferent fibers in other target tissues, such as the salivary glands.

Endothelin-1-induced depolarization and hyperpolarization in submandibular ganglion neurons

The effects of endothelin-1 were studied in vitro on neurons in the hamster submandibular ganglion, using the intracellular microelectrode technique. Endothelin (1 microM) caused a depolarization (5.5 +/- 1.2 mV) followed by a hyperpolarization (8.5 +/- 2.8 mV) of the membrane potential. Membrane conductance was increased during the endothelin-induced depolarization and was decreased during the endothelin-induced hyperpolarization. The endothelin-induced depolarization was depressed (mean 43.6%) in a Krebs solution containing zero calcium and high magnesium. The results suggested that the predominant component of the depolarization was mediated by calcium ions. The calcium-insensitive component of depolarization was carried by chloride ions. Endothelin-induced slow rhythmic hyperpolarizations were probably induced by a decrease in chloride ion conductance.

Surgical release of a stone from the hilum of the submandibular gland: a technique note

A minimally invasive surgical technique using an intra-oral approach for release of salivary stones from the proximal submandibular duct and hilum is described in detail. The different surgical steps are illustrated.

Preganglionic parasympathectomy decreases salivary SIgA secretion rates from the rat submandibular gland

Immunoglobulin A (IgA) is transported into saliva by salivary cells expressing the polymeric immunoglobulin receptor (pIgR). In rat salivary glands, autonomic nerves stimulate this process. To examine how nerves affect pIgR-mediated IgA secretion, the chorda-lingual nerve was sectioned. One week after preganglionic parasympathectomy, both the stimulated and unstimulated rates of salivary IgA secretion were reduced, despite similar glandular amounts of IgA. Biochemical analysis of cells from parasympathectomised and control glands indicated reduced membrane expression of pIgR. It appears the removal of long-term parasympathetic input has affected the routing of pIgR within salivary cells and reduced the SIgA transport into saliva.

The effect of nerve growth factor on functional recovery after injury to the chorda tympani and lingual nerves

Nerve growth factor (NGF) is known to ameliorate central changes and enhance the regeneration of damaged axons in the early stages after peripheral nerve injury. We have assessed the long-term outcome of placing NGF at a nerve repair site by determining the functional characteristics of several groups of sensory afferent and autonomic efferent fibres in the cat lingual nerve. Six months after entubulation repair, with or without the incorporation of NGF, the recovery of secretomotor and vasomotor efferents was determined by recording salivary flow from the submandibular gland and temperature changes on the tongue surface, each evoked by stimulation of the repaired nerve. Electrophysiological recordings from the lingual and chorda tympani nerves proximal to the repair allowed characterisation of mechanosensitive, thermosensitive and gustatory afferents. When compared with data from uninjured control animals, both repair groups showed changes in spontaneous discharge and persistent reductions in conduction velocity, receptor sensitivity, proportion of gustatory units, and rate of salivary secretion. Comparisons between the outcome of repair with or without NGF revealed few differences. In the NGF group the conduction velocity of afferents in the lingual nerve was lower, and the level of spontaneous activity was higher. However, NGF appeared to preferentially enhance the regeneration of thermosensitive afferents, suggesting that it may play a role in determining the phenotypic profile of the regenerating axonal population. This suggests that future therapeutic enhancement of regeneration after peripheral nerve injury may require a combination of factors to encourage regeneration of specific fibre groups.

Nitric oxide-dependent mitotic activity in salivary glands of the rat upon sympathetic stimulation

Incorporation of [3H]thymidine into trichloroacetic acid (TCA)-insoluble material of the parotid and submandibular glands was used as an index of mitotic activity following unilateral electrical stimulation of the sympathetic innervation (20 Hz, 4 min every fifth minute over 34 min). Stimulation under beta-adrenoceptor blockade (propranolol 2 mg/kg, intravenous) alone or combined with alpha-adrenoceptor blockade (phentolamine 2 mg/kg, intravenous) did not increase the rate of [3H]thymidine incorporation into the two types of glands. However, under alpha-adrenoceptor blockade the [3H]thymidine incorporation increased into the parotid glands, by 122% (compared to the glands on the contralateral side), but not into the submandibular glands. In the presence of the neuronal type NO-synthase (nNOS) blocker N-PLA (30 mg/kg, intravenous) or the unselective NO-synthase blocker L-NAME (30 mg/kg, intravenous), this increase was reduced to 49 and 47%, respectively. Thus, the major part of the sympathetically nerve-evoked beta-adrenoceptor-mediated mitotic response was found to depend on the activity of neuronal type NO-synthase to generate NO. Since the sympathetic nerve fibres of the parotid gland lack NO-synthase, the neuronal type NO-synthase subjected to the inhibitors is likely to be of parenchymal origin.

Comparison of target innervation by sympathetic axons in adult wild type and heterozygous mice for nerve growth factor or its receptor trkA

Nerve growth factor (NGF), a neurotrophin required for the survival and maintenance of postganglionic sympathetic neurons, mediates its trophic effects by activation of its high-affinity receptor trkA. Null mutant mice lacking either NGF or trkA have profound sympathetic deficits, thus revealing the vital importance of NGF synthesis in target tissues and trkA expression by sympathetic neurons. In this study, we sought to assess whether sympathetic neurons of the superior cervical ganglion (SCG) display alterations in their neurochemical phenotype in adult mice carrying one mutated allele for either NGF or trkA, and whether such differences result in altered patterns of innervation to the submandibular salivary gland and pineal gland. In comparison with adult siblings, levels of trkA protein in the SCG were reduced in age-matched NGF(+/-) and trkA(+/-) mice. While NGF(+/-) mice also had significantly fewer sympathetic axons innervating both the submandibular salivary gland and pineal gland, densities of sympathetic axons in both tissues reached normal levels in trkA(+/-) mice. These findings reveal that while levels of trkA are reduced in SCG neurons of adult NGF(+/-) and trkA(+/-) mice (compared with their wild type counterparts), sympathetic axons are capable of achieving normal patterns of target innervation in trkA(+/-) mice but not in NGF(+/-) mice. As NGF protein levels are not depleted in the submandibular salivary gland and pineal gland of NGF(+/-) mice, a loss of sympathetic neurons [Nat Neurosci 1999; 2:699-705], in combination with reduced levels of trkA protein, may account for perturbed patterns of sympathetic innervation to peripheral tissues.

A quantitative study of nerve fiber density in the submandibular gland of rats

The route and three dimensional distribution of nerve terminals in the submandibular gland were investigated in rats using immunohistochemistry for the protein gene product (PGP) 9.5, as a marker of neuronal elements. Thick fiber bundles were found along the wall of the excretory duct. Many fine fibers from these thick bundles were distributed each lobule of the submandibular gland. A large number of single fibers terminated in the area around the striated, intercalated ducts and the acini. The densities of PGP 9.5 immunoreactive terminals were measured by a computer aided analysis system in the three areas: the striated duct, the intercalated duct, and the acini, whose densities (microm/microm2) were 0.23, 0.39 and 0.05 respectively. The relatively high density of nerve terminals in the intercalated duct suggests that the duct system probably plays an unexpectedly important role in the functional aspects.

Co-expression of tyrosine hydroxylase, dopamine beta-hydroxylase and neuropeptide Y in the sympathetic neurons projecting to the submandibular gland in the sheep

Sympathetic neurons projecting to the ovine submandibular gland (SMG) from the superior cervical ganglion (SCG) and middle cervical ganglion (MCG) were identified using retrograde tracing with fluorescent dye (Fast Blue). Antibodies to tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH) and neuropeptide Y (NPY) were used to determine the immunochemical characteristics of SMG-innervating sympathetic neurons. Immunohistochemistry combined with the retrograde tracing revealed that the population of SMG-projecting neurons consist of four distinct sub-populations, but taking into account their possible different physiological properties only three major sub-populations can be distinguished. The vast majority of neurons in both ganglia are noradrenergic in nature (co-express TH and DbetaH). All examined TH-immunoreactive (IR) neurons also show immunoreactivity to DbetaH. Sub-population of noradrenergic neurons can be divided into NPY-IR and non-NPY-IR. Noradrenergic neurons expressing NPY may act as vasoconstrictors. The second sub-population of SMG projecting neurons in the ganglia studied consists of non-noradrenergic neurons (containing NPY, but not TH). It is known that these kinds of neurons may play a vasodilatory role. In both examined ganglia the third sub-population consists of non-TH-IR and non-NPY-IR neurons of unknown physiological function. Since no DbetaH immunoreactivity was found in any of TH- neurons these nerve cells can also be regarded as non-noradrenergic. It is possible that some neurons of the second as well as the third sub-population are cholinergic and some of them are non-noradrenergic/non-cholinergic in character.

Multiple signal pathways coupling VIP and PACAP receptors to calcium channels in hamster submandibular ganglion neurons

The Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are two novel neuropeptides which produce particular biological effects caused by interaction with G-protein-coupled receptors. We have shown in a previous study where VIP and PACAP 38 inhibit voltage-dependent calcium channel (VDCC) currents (ICa) via G-proteins in hamster submandibular ganglion (SMG) neurons. In this study, we attempt to further characterize the signal transduction pathways of VIP-and PACAP 38-induced modulation of ICa. Application of 1 microM VIP and PACAP 38 inhibited ICa by 33.0 +/- 3.1% and 36.8 +/- 2.6%, respectively (mean +/- S.E.M., n = 8). Application of strong voltage prepulse attenuated PACAP 38-induced inhibition of ICa. Pretreatment of cAMP dependent protein kinase (PKA) activator attenuated VIP-induced inhibition, but not the PACAP 38-induced inhibition. Intracellular dialysis of the PKA inhibitor attenuated the VIP-induced inhibition, but not the PACAP 38-induced inhibition. Pretreatment of protein kinase C (PKC) activator and inhibitor attenuated VIP-induced inhibition, but not the PACAP 38-induced inhibition. Pretreatment of cholera toxin (CTX) attenuated PACAP 38-induced inhibition of ICa. These findings indicate that there are multiple signaling pathways in VIP and PACAP 38-induced inhibitions of ICa: one pathway would be the VPAC1/VPAC2 receptors-induced inhibition involving both the PKA and PKC, and another one concerns the PAC1 receptor-induced inhibition via Gs-protein betagamma subunits. The VIP-and PACAP 38-induced facilitation of ICa can be observed in the SMG neurons in addition to inhibiting of ICa.

Neural regulation of submandibular gland blood flow in the streptozotocin-diabetic rat: evidence for impaired endothelium-dependent vasodilatation

Functional changes in vascular tone and reactivity arise early in diabetes, and endothelial dysfunction plays a central role in the development of these microvascular abnormalities. Blood flow in the rat submandibular gland is mainly under neural regulation, which is mediated in part via endothelium-dependent mechanisms. Given the role of the endothelium in regulating blood flow and the deleterious effects of diabetes on endothelial cell function, we hypothesised that diabetes would significantly impair neural regulation of submandibular gland vascular perfusion. Three weeks after the induction of streptozotocin diabetes continuous 2 Hz sympathetic stimulation resulted in a similar degree of vasoconstriction (as measured by a decrease in perfusion) in both diabetic (-31+/-17%) and control rats (-22+/-7%). However, the magnitude and the duration of the after-dilatation were significantly less in diabetic animals. The same number of impulses delivered at 20 Hz in bursts (1s in every 10s) also resulted in vasoconstriction with each burst, but unlike the effects of burst stimulation in control rats the initial vasoconstriction was not converted to a net vasodilatation between bursts. Parasympathetic stimulation (2, 5 and 10 Hz) caused a marked vasodilatation in both control and diabetic rats, but the initial responses were delayed in diabetic animals, the maintained phases were smaller in magnitude (P<0.02) and it took longer to return to resting levels. In conclusion, submandibular gland vascular responses are altered in streptozotocin-induced diabetic rats. Vasoconstrictor responses evoked by sympathetic impulses were unaffected, but vasodilatory responses, particularly those associated with endothelium-dependent mechanisms, were significantly reduced.

Ionotropic NMDA receptor evokes an excitatory response in superior salivatory nucleus neurons in anaesthetized rats

Extracellular recordings were taken from preganglionic superior salivatory nucleus (SSN) neurons projecting to submandibular and intra-lingual ganglia, in order to study the action of SSN neurons resulting from ionophoretic application of ionotropic NMDA receptor agonist in urethane-chloralose anaesthetized rats. Single SSN neurons were identified by their antidromic spike responses following stimulation of the chorda-lingual nerve (CLN), chorda tympani branches (CTBs) and the lingual nerve (LN). About one-third (33%, 10/30) of the identified SSN neurons were induced to fire by ionophoretic application of the NMDA receptor agonists used, dl-homocysteic acid (DLH) and N-methyl-D-aspartic acid (NMDA). More than half exhibited firing at high frequencies, often exceeding 40 Hz. About one-fifth (20%; 6/30) of the identified SSN neurons exhibited orthodromic spike responses to the combination of NMDA receptor agonist application and sensory nerve (CLN or LN) stimulus. These excitatory responses evoked by application of NMDA receptor agonist were attenuated (n = 4) by ionophoretic application of DL-2-amino-5-phosphonovaleric acid (AP5; NMDA receptor antagonist). About half (47%) of the neurons did not respond to any combination of NMDA receptor agonist and sensory nerve stimuli. No differences were observed between SSN neurons with B fibre axons and those with C fibre axons in response to ionophoresis of the NMDA receptor agonists. The NMDA-sensitive neurons, which exhibited high frequency firing, were predominantly found in the rostral part of the SSN. In summary, activation of ionotropic NMDA receptors exerts an excitatory effect on about half of the SSN neurons. These data support the view that NMDA receptors are involved in information processing and transmission on SSN neurons.

Distribution of sympathetic and afferent neurones innervating the submandibular gland in the sheep

The distribution of sympathetic and sensory neurones innervating the submandibular gland (SMG) in sheep was studied using retrograde tracing technique. The retrograde tracer Fast Blue (FB) was unilaterally injected into the SMG in five juvenile male sheep under general anaesthesia. After a 4-week survival period, all the animals were reanaesthetized, perfused transcardially with 4% buffered paraformaldehyde and ganglia, which could be considered as a potential sources of sympathetic, and afferent innervation of the gland were bilaterally collected. The FB-labelled sympathetic neurones were found in the ipsilateral superior and middle cervical ganglion. Many labelled neurones were distributed in the ipsilateral jugular and nodose ganglia of the vagus nerve and smaller numbers of the nerve cells were also found in ipsilateral C1-C3 dorsal root ganglia (DRG). No labelled neurones were observed in the ipsilateral stellate ganglion, trigeminal ganglion, C4-C8 DRG and in all contralateral ganglia. The present study revealed that the majority of sympathetic neurones projecting to the sheep SMG are found in the superior cervical ganglion but some of them are also distributed in the middle cervical ganglion. Most of the afferent neurones are located in the jugular and nodose ganglia of vagus nerve but C1-C3 DRG also comprise some of these nerve cells.

Postdecentralization plasticity of voltage-gated Na+ currents in rat glandular sympathetic neurons

The kinetic properties of voltage-gated Na(+) currents in two groups of glandular postganglionic sympathetic neurons were assessed. The first group of neurons remained innervated by preganglionic axons until the day of current recordings, while the second--decentralized 4 weeks prior to recordings. An increase of maximum current amplitude and density was noted in decentralized neurons. Na(+) currents activated and time-dependently inactivated more slowly in decentralized than in control neurons. Furthermore, after decentralization the currents steady-state inactivated at less hyperpolarized potentials as well as reactivated faster from inactivation. We conclude that the Na(+) currents in decentralized postganglionic glandular sympathetic neurons undergo up-regulation.

Angiotensin II-induced ionic currents and signalling pathways in submandibular ganglion neurons

Angiotensin II (Ang II) 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 system. The submandibular ganglion (SMG) neuron is a parasympathetic ganglion which receives inputs from preganglionic cholinergic neurons, and innervates the submandibular salivary gland to control saliva secretion. In this study, the effects of Ang II on SMG neurons were investigated using the whole-cell patch clamp technique. Membrane currents evoked by a ramp pulse from +50 to -100 mV (-150 mV/500 ms) were compared in both the absence and presence of Ang II. In eight neurons tested, 1 microM Ang II increased inward currents by 42.0+/-8.2%. The reversal potentials of the Ang II-induced current were 0.2+/-0.6 mV. These increase of inward currents by Ang II were antagonized by losartan, a selective antagonist of AT(1) receptors. Intracellular dialysis with 0.1mM guanosin 5'-O-(2-thiodiphosphate) (GDP-beta-S), a G-proteins blocker, and anti-G(q/11) antibody attenuated Ang II-induced ionic current. In addition, pretreatment of neurons with 10 microM staurosporine (stauro), a protein kinase C (PKC) inhibitor, 0.5 microM PMA, a PKC activator, and 10 microM KN-93, a Ca2+/calmodulin-dependent protein kinase II (CaM K II) inhibitor, attenuated Ang II-induced ionic current in SMG neurons. The data presented here demonstrated that Ang II-induced ionic current via G(q/11)-proteins involving both PKC and CaM K II pathways in SMG neurons.

Salivary secretion of immunoglobulin A by submandibular glands in response to autonomimetic infusions in anaesthetised rats

Salivary secretion of immunoglobulin A (lgA) by submandibular glands is increased by stimuli from autonomic nerves. Since it is unclear which specific autonomic receptors transduce such stimuli, we have infused autonomimetics intravenously and compared secretion of fluid, IgA and stored proteins (peroxidase and total protein) with secretory responses during electrical stimulation of the parasympathetic nerve supply in anaesthetized rats. The greatest secretion of IgA was evoked by the alpha-adrenoceptor agonist phenylephrine and this was reduced by the beta-adrenoceptor blocking drug propranolol. The secretion of fluid or proteins but not IgA was increased with frequency of nerve stimulation and dose of methacholine (cholinergic), isoprenaline (beta-adrenergic) or phenylephrine (alpha-adrenergic).

The effects of the chorda tympani damage on submandibular glands: biometric changes

OBJECTIVE

It was aimed to analyze the biometric changes in ipsilateral submandibular glands of patients with unilateral chorda tympani (ChT) section during otological operations, compared with change in size of the contralateral glands and with those of healthy subjects.

METHODS

29 patients with unilateral complete ChT section and 29 healthy subjects with identical ages, genders, and weights to the patient group were examined ultrasonographically. The patients having a mean duration to follow-up examination of 32 months (2-84 months) were subdivided into two groups by their time to follow-up as short-term patient group (2-12 months, 14 patients) and long-term patient group (13-84 months, 15 patients). The ultrasonographic dimensions and volumes of submandibular glands were compared statistically between the groups.

RESULTS

In the patient group, the glands on the contralateral, non-operated side were found to be greater than the ipsilateral, denervated glands in terms of both paramandibular depth dimension (P<0.05) and volume (P<0.01). The differences could be determined only in long-term patient group. When comparing the submandibular glands of the patient group with those of the control group, it was found that paramandibular depth dimension and volume of the submandibular glands on the contralateral, non-operated side were statistically greater (P<0.01). There was no difference between submandibular glands on the operated side of the patient group and those of the control group (P>0.05).

CONCLUSION

The late (13-84 months) biometric results of ChT damage on submandibular gland were significant for increase in the size of the contralateral, non-denervated submandibular gland. An atrophying effect was not ascertained in the submandibular glands denervated parasympathetically due to the section of the ChT.

Autonomic nervous control of myoepithelial cells and secretion in submandibular gland of anaesthetized dogs

In dog submandibular gland, the activity of myoepithelial cells was assessed by simultaneous measurement of intraductal pressure (P(du)) and subcapsular pressure (P(ca)) using catheter-tip pressure transducers; their resting values were 2.5 +/- 0.21 and 3.0 +/- 0.19 mmHg, respectively (n = 40). Retrograde infusion of saliva (collected from preceding parasympathetic nerve stimulation) increased P(du) (coefficient of 50 mmHg ml(-1) for rates < 1 ml min(-1) and 85 mmHg ml(-1) for higher rates) and P(ca) (coefficient of 0.47 mmHg ml(-1) for all rates). Blood flow changes did not affect P(du) but increased P(ca) (coefficient of 0.04 mmHg ml(-1)). Parasympathetic nerve stimulation increased P(du) but decreased P(ca) abruptly; the response threshold was 0.1 Hz, with maximal responses at 16 Hz. The coefficients for P(du) and P(ca) on salivary secretion to parasympathetic nerve stimulation in glands with spontaneous blood flow (5.3 x 10(-3) and 4.87 x 10(-2) ml min(-1) g(-1) mmHg(-1)) were close to their values in glands with constant-flow vascular perfusion (4.9 x 10(-3) and 3.68 x 10(-2) ml min(-1) g(-1) mmHg(-1)). The finding that P(ca) fell despite concomitant increased blood flow suggests contraction of myoepithelial cells. Additional ductal occlusion further increased P(du) and enhanced the fall in P(ca), suggesting that the myoepithelial cells can contract when distended. Atropine blocked salivary secretion and responses of P(du) and P(ca) to parasympathetic nerve stimulation. ACh elicited responses similar to that of parasympathetic nerve stimulation. VIP caused very scanty salivary secretion and gradual slight increases in P(du) and P(ca); the change in P(ca) was abolished in glands with constant-flow vascular perfusion. Hence, contraction of myoepithelial cells to parasympathetic nerve stimulation is via muscarinic receptors. Sympathetic nerve stimulation increased P(du) and decreased P(ca) abruptly; the response threshold was 0.1 Hz, with maximal responses at 16 Hz. The coefficients for P(du) and P(ca) on salivary secretion to sympathetic nerve stimulation in glands with spontaneous blood flow (3.0 x 10(-3) and 3.2 x 10(-3) ml min(-1) g(-1) mmHg(-1)) were similar to their values in glands with constant-flow vascular perfusion (3.2 x 10(-3) and 3.1 x 10(-3) ml min(-1) g(-1) mmHg(-1)). The finding that P(ca) fell even in glands with constant-flow vascular perfusion suggests contraction of myoepithelial cells. Superimposed sympathetic nerve stimulation immediately enhanced the pressure changes and secretory response to parasympathetic nerve stimulation, indicating that the two autonomic nerves act synergistically to evoke myoepithelial cell contraction. Phentolamine and prazosin but not propranolol and yohimbine blocked the sympathetic enhancement. The finding that phenylephrine, but not clonidine and isoproterenol, abruptly decreased P(ca) in glands with constant-flow vascular perfusion suggests that the sympathetic activation of myoepithelial cells is via the alpha(1)-adrenoceptors.

Presynaptic muscarinic receptor mechanisms and submandibular responses to stimulation of the parasympathetic innervation in bursts in rats

Submandibular secretory responses to electrical stimulation of the parasympathetic innervation at variable frequencies were measured in anaesthetized rats. Selective blockade by pirenzepine and by methoctramine occurred at doses (50 and of 300 nmol kg (-1), i.v., respectively) that did not inhibit the responses to exogenous acetylcholine. In the presence of methoctramine, the nerve-evoked fluid responses were increased by 100% at 1 Hz independently of the total number of impulses (10-300), suggesting that M2 receptor activation inhibits transmitter release. The magnitude of the increase was inversely related to frequency of stimulation. The protein concentrations in the fluid responses were not significantly affected by methoctramine. Pirenzepine had an inhibitory effect on the fluid secretory responses, which was dependent of frequency, as well as of number of impulses, suggesting that M1 receptor activation facilitates transmitter release. At 10 Hz given intermittently (for 1 s at 10-s intervals), pirenzepine reduced the fluid response by 25%. The protein release was substantially and significantly reduced by pirenzepine independent of frequency but only during long periods of stimulation (300 impulses). It is concluded that muscarinic M1 receptor activation normally has a facilitatory effect on transmitter release, and that the facilitation occurs during short, intense stimulation. Muscarinic M1 receptors are, however, likely to regulate protein secretion by other mechanisms. Muscarinic M2 receptors, on the other hand, normally inhibit cholinergic transmission at low frequencies. Similar to findings in the alimentary tract of several species, stimulation in bursts at high frequencies is a more efficient stimulation pattern than continuous low frequency stimulation. This pattern of stimulation thus takes advantage of transient facilitation and avoids the inhibition at less intense neuronal activity.

Constitutive secretion of immunoglobulin A and other proteins into lumina of unstimulated submandibular glands in anaesthetised rats

Salivary fluid secretion is dependent upon reflex stimuli mediated by autonomic nerves. In order to determine if immunoglobulin A (IgA) and salivary proteins are secreted in the absence of nerve stimulation, small volumes (< 2 microl) of saliva were consecutively collected from the submandibular duct of anaesthetised rats following rest pauses in order to sample the protein contents of the ductal system. Within the first 5 microl of such saliva collected by parasympathetic nerve stimulation, IgA and other salivary proteins reached peak concentrations that were over 20-fold greater than levels in parasympathetically stimulated saliva subsequently collected during a 5 min period of stimulation. Confocal microscopy of TRITC-labelled IgA added to live, acutely isolated submandibular acini indicated that it did not enter the lumina by paracellular leakage. IgG is thought to enter saliva by paracellular leakage but did not accumulate in luminal saliva in the present study. Electrophoresis suggested that the major proteins secreted in the absence of stimulation were the same as those present in subsequently stimulated saliva. It can be concluded that IgA and other major submandibular proteins are secreted into glandular lumina in the absence of nerve stimulation. The functional significance of such unstimulated protein secretion is at present unclear.

Constitution of calcium channel current in hamster submandibular ganglion neurons

The submandibular ganglion (SMG) neuron has been well established as the parasympathetic ganglion that innervates the submandibular and sublingual salivary glands. Thus this neuron plays a key role in salivary secretion. In a previous study, we reported that SMG possessed T-, L-, N-, P/Q- and R-type voltage-dependent calcium channels (VDCCs). In this study, we analyzed the contribution of the distinct subtypes of VDCCs currents (ICa) using the whole-cell configuration of the patch clamp technique in SMG neurons. In addition, we also investigated the effects of a strong voltage prepulse on the contributions of the subtypes of VDCCs. In SMG neuronal ICa without a prepulse, the mean percentages of L-, N-, P-, Q- and R-type were 39.7, 31.5, 10.6, 7.1 and 7.9%. In SMG neuronal ICa with prepulse, the mean percentages of L-, N-, P-, Q- and R-type were 37.2, 34.0, 14.0, 7.6 and 7.0%. Thus, these results showed that SMG possess multiple types of VDCCs and that N- and P-type VDCCs are facilitated by a prepulse in SMG neurons.

Effects of endothelin on submandibular salivary responses to parasympathetic stimulation in anaesthetized sheep

Submandibular responses to stimulation of the parasympathetic chorda tympani nerve have been investigated in anaesthetized sheep before, during and after an intracarotid infusion of endothelin, which reduced the blood flow through the gland by 56+/-5%. Stimulation of the peripheral end of the chorda tympani nerve produced a frequency-dependent increase in the flow of submandibular saliva, and in sodium, potassium and protein output. The reduction in submandibular blood flow, which occurred in response to endothelin, was associated with a decrease in the flow of saliva at all frequencies tested amounting on average to 44+/-6% (P<0.01). The flow of saliva was linearly related to the blood flow before and after endothelin. Both parameters were also linearly related during the infusion of endothelin and the regression lines were parallel. Salivary sodium concentration was significantly increased at the lower frequencies (1 and 2 Hz). Protein output was generally reduced but the difference only achieved statistical significance during stimulation at 1 Hz (P<0.01). Thus, submandibular secretory responses to parasympathetic stimulation are significantly attenuated by reducing the blood flow through the gland in this way.

Angiotensin II-induced inhibition of calcium currents via G(q/11)-protein involving protein kinase C in hamster submandibular ganglion neurons

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 microM 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.

Cyclic AMP-dependent protein kinase-independent angiotensin II-induced inhibition of calcium current in hamster submandibular ganglion neurons

In a previous study, we demonstrated that angiotensin II (AngII) inhibited voltage-dependent calcium channels (VDCCs) currents (ICa) in hamster submandibular ganglion (SMG) neurons. In sinoatrial node cells, it has been reported that AngII 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 AngII-induced inhibition of ICa, effects of AngII 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 AngII-induced inhibition of ICa. These results indicate that AngII inhibited ICa via a cyclic AMP-PKA-independent mechanism in SMG neurons.

VIP and PACAP inhibit L-, N- and P/Q-type Ca2+ channels of parasympathetic neurons in a voltage independent manner

In this study, we investigated the effects of vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide 1-38 (PACAP) on the voltage-gated calcium currents in hamster submandibular ganglion neurons. VIP and PACAP inhibited the high threshold voltage-gated calcium current in a voltage-independent and a concentration-dependent manner via the G protein-mediated pathway. L-, N- and P/Q-type components of the total maximum voltage-gated calcium current accounted for 48.0 +/- 3.1% (n = 4), 35.1 +/- 4.7% (n = 4), and 13.5 +/- 2.3% (n = 3) of the total peak amplitude, respectively. VIP at a concentration of 1 microM inhibited the L-type calcium current by 33.2% +/- 1.4% (n = 4), the N-type current by 31.0 +/- 3.6%, and the P/Q-type current by 3.2 +/- 1.1% (n = 3). PACAP at a concentration of 1 microM inhibited the L-type current by 35.6 +/- 5.7%, the N-type current by 34.4 +/- 3.1% (n = 4), and the P/Q-type current by 6.4 +/- 2.1% (n = 2). However, VIP and PACAP did not inhibit the low threshold voltage-gated (T-type) calcium current. The rank order of potency was PACAP > VIP. In experiments replacing GTP with GDP-beta-S, the inhibitory effects of VIP and PACAP were prevented. In experiments of double-pulse protocol, depolarizing conditioning pulses could not relieve the inhibition of total high threshold voltage-gated calcium currents produced by VIP and PACAP. Therefore, the inhibition of the high threshold voltage-gated calcium channels produced by VIP and PACAP in hamster parasympathetic neurons differed in its mechanisms from that of N-type calcium channels in rat sympathetic neurons.