Neuropeptide Y in salivary glands of the rat: origin, release and secretory effects

The human major sublingual gland and its neuropeptidergic and nitrergic innervations

BACKGROUND

What textbooks usually call the sublingual gland in humans is in reality a tissue mass of two types of salivary glands, the anteriorly located consisting of a cluster of minor sublingual glands and the posteriorly located major sublingual gland with its outlet via Bartholin's duct. Only recently, the adrenergic and cholinergic innervations of the major sublingual gland was reported, while information regarding the neuropeptidergic and nitrergic innervations is still lacking.

METHODS

Bioptic and autoptic specimens of the human major sublingual gland were examined by means of immunohistochemistry for the presence of vasoactive intestinal peptide (VIP)-, neuropeptide Y (NPY)-, substance P (SP)-, calcitonin gene related-peptide (CGRP)-, and neuronal nitric oxide synthase (nNOS)-labeled neuronal structures.

RESULTS

As to the neuropeptidergic innervation of secretory cells (here in the form of mucous tubular and seromucous cells), the findings showed many VIP-containing nerves, few NPY- and SP-containing nerves and a lack of CGRP-labeled nerves. As to the neuropeptidergic innervation of vessels, the number of VIP-containing nerves was modest, while, of the other neuropeptide-containing nerves under study, only few (SP and CGRP) to very few (NPY) nerves were observed. As to the nitrergic innervation, nNOS-containing nerves were very few close to secretory cells and even absent around vessels.

CONCLUSION

The various innervation patterns may suggest potential transmission mechanisms involved in secretory and vascular responses of the major sublingual gland.

Aging-Related Metabolic Dysfunction in the Salivary Gland: A Review of the Literature

Aging-related salivary dysfunction commonly induces the poor oral health, including decreased saliva flow and dental caries. Although the clinical significance of the salivary glands is well-known, the complex metabolic pathways contributing to the aging-dysfunction process are only beginning to be uncovered. Here, we provide a comprehensive overview of the metabolic changes in aging-mediated salivary gland dysfunction as a key aspect of oral physiology. Several metabolic neuropeptides or hormones are involved in causing or contributing to salivary gland dysfunction, including hyposalivation and age-related diseases. Thus, aging-related metabolism holds promise for early diagnosis, increased choice of therapy and the identification of new metabolic pathways that could potentially be targeted in salivary gland dysfunction.

Distribution, nature, and origin of CXCL14-immunoreactive fibers in rat parotid gland

The distribution and nature of CXCL14-immunoreactive nerve fibers in salivary glands, especially the parotid gland was immunohistochemically investigated. Furthermore, the origin of parotid CXCL14-immunoreactive nerve fibers was determined by retrograde tracing experiments. CXCL14-immunoreactive nerve fibers were localized in the parotid, submandibular, and sublingual glands, particularly in the parotid gland. Double staining using identical sections revealed that a subpopulation of cells neuropeptide Y (NPY)-containing fibers was immunopositive for CXCL14 in the parotid gland. In the peripheral regions of acinar cells, CXCL14-immunoreactive fibers tended to coexist with NPY; however, perivascular NPY-immunoreactive fibers tended to be immunonegative for CXCL14. Parotid CXCL14-immunoreactive fibers were immunopositive for tyrosine hydroxylase (TH) but immunonegative for choline acetyltransferase and vasoactive intestinal peptide (VIP). After injection of horseradish peroxidase-labeled wheat germ agglutinin (WGA-HRP) in the parotid gland, retrogradely labeled neurons were seen in the superior cervical ganglion (SCG) and otic ganglion. Some of the WGA-immunoreactive somata in the SCG were immunopositive for CXCL14; however, no doubly-labeled somata were noted in the otic ganglion. These results indicate that CXCL14-immunoreactive nerve fibers originate in the SCG, and are sympathetic in nature. The coexistence of CXCL14 with NPY/TH suggests that CXCL14 may be associated with NPY/TH functions as a neuromodulatory chemokine in the parotid gland. The localization of CXCL14 nerve fibers around the acinar cells of the parotid gland indicates its involvement in acinar cell function, but not vasoconstriction.

Effect of the neuropeptides vasoactive intestinal peptide, peptide histidine methionine and substance P on human major salivary gland secretion

OBJECTIVE

The parasympathetic transmitters vasoactive intestinal peptide (VIP) and substance P (SP) are secretagogues in salivary glands of animals. Currently, we hypothesise that in human salivary glands, these neuropeptides and the VIP-related peptide histidine methionine (PHM) also exert secretory actions, reflected morphologically by exocytosis of acinar protein/glycoprotein-storing granules.

MATERIALS AND METHODS

Submandibular and parotid gland tissues, exposed in vitro to VIP and PHM, and SP, respectively, were examined by light and transmission electron microscopy. For comparison, the response to in vitro stimulation of isoproterenol, phenylephrine and carbachol was examined. Moreover, the peptidergic innervation of the glands was examined by immunohistochemistry.

RESULTS

Vasoactive intestinal peptide- and PHM-immunoreactive nerves were in close proximity to acini and ducts in the two glands, while these elements lacked a SP-positive innervation. While no morphological changes occurred in response to SP (parotid glands), VIP and PHM administration (submandibular glands) caused conspicuous acinar degranulation accompanied by luminal space broadening. In the two glands, both α1 - and β-adrenergic receptor stimulation and muscarinic receptor stimulation caused similar changes as to VIP/PHM, although to varying extent.

CONCLUSIONS

Vasoactive intestinal peptide and PHM, but not SP, are likely transmitters in the parasympathetic control of salivary (protein) secretion in humans.

Neuropeptide Y modulates calcium channels in hamster submandibular ganglion neurons

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.

Neurochemical classification and projection targets of CART peptide immunoreactive neurons in sensory and parasympathetic ganglia of the head

The aims of the present study were to determine if there is neuronal Cocaine and amphetamine regulated transcripts (CART) peptide expression (CART+) in parasympathetic (sphenopalatine (SPG); otic (OG)) and sensory (trigeminal (TG)) ganglia of the head and to examine the neurochemical phenotype (calcitonin gene-related peptide (CGRP), neurofilament 200 (NF200), isolectin B4 (IB4) binding, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and enkephalin (ENK) immunoreactivity) and projection targets (lacrimal gland (LG), parotid gland (PG), nasal mucosa (NM), temporomandibular joint (TMJ), middle cerebral artery (MCA) and middle meningeal artery (MMA)) of CART expressing neurons in these ganglia. We found CART+ neurons in both the SPG (5.25±0.07%) and OG (4.32±0.66). A significant proportion of these CART+ neurons contained VIP, NPY or ENK (34%, 26% and 11%, respectively). SPG neurons retrogradely labelled from the lacrimal gland (29%) were CART+, but we were unable to demonstrate CART+ labelling in any of the SPG or OG neurons labelled from other targets. This supports a role for CART peptides in lacrimation or regulation of vascular tone in the lacrimal gland, but not in salivation or nasal congestion. CART+ neurons were also present in the trigeminal ganglion (1.26±0.38%), where their size distribution was confined almost completely to neurons smaller than 800 μm2 (mean=410 μm2; 98%<800 μm2), and were almost always CGRP+, but did not bind IB4. This is consistent with a role for CART peptides in trigeminal pain. However, there were few CART+ neurons amongst any of the trigeminal neurons retrogradely labelled from the targets we investigated and thus we cannot comment on the tissue type where such pain may have originated. Our study shows that some specialization of CART peptide expression (based on neurochemical phenotype and target projection) is evident in sensory and parasympathetic ganglia of the head.

Immunohistochemical characterization of superior cervical ganglion neurons supplying porcine parotid salivary gland

The main goal of our study was to investigate the chemical coding of the superior cervical ganglion (SCG) sympathetic neurons supplying the porcine parotid gland. Additionally, the chemical nature of the vicinal nerve fibers surrounding the parotid SCG perikarya was investigated. Fast blue (FB) retrograde tracing of the parotid gland and immunofluorescent labelling of SCG neurons were studied in juvenile female pigs. Microscopic analysis revealed that only ipsilateral SCG neurons were retrogradely labelled. The labelled neurons formed a discrete cluster in the middle and caudal region of the ganglion. Immunofluorescent labelling revealed that virtually all of the FB-positive parotid gland neurons were immunoreactive to tyrosine hydroxylase (TH), confirming their sympathetic nature. In addition to TH, the majority of the FB-positive neurons were found to be immunoreactive to calbindin (CB) and to a lesser extent for neuropeptide Y (NPY), leu-enkephalin (LENK) and galanin (GAL). In the close proximity of the FB-traced perikarya, a large number of immunoreactive (IR) vasoactive intestinal peptide (VIP-IR), pituitary adenylate cyclase-activating polypeptide (PACAP-IR), nitric oxide synthase (NOS-IR) processes were identified. Moreover, calcitonin gene related peptide-immunoreactive (CGRP-IR), substance P-immunoreactive (SP-IR), vesicular acetylcholine transporter (VAChT-IR), calretinin (CRT-IR), GAL-IR, LENK-IR and CB-IR protrusions were observed. The results of the present study provide a detailed characteristic of the location and neurochemical coding of sympathetic SCG neurons innervating the parotid salivary gland of the pig and lay ground for more advanced, clinical studies on salivary gland innervations.

Chemical coding for cardiovascular sympathetic preganglionic neurons in rats

Cocaine and amphetamine-regulated transcript peptide (CART) is present in a subset of sympathetic preganglionic neurons in the rat. We examined the distribution of CART-immunoreactive terminals in rat stellate and superior cervical ganglia and adrenal gland and found that they surround neuropeptide Y-immunoreactive postganglionic neurons and noradrenergic chromaffin cells. The targets of CART-immunoreactive preganglionic neurons in the stellate and superior cervical ganglia were shown to be vasoconstrictor neurons supplying muscle and skin and cardiac-projecting postganglionic neurons: they did not target non-vasoconstrictor neurons innervating salivary glands, piloerector muscle, brown fat, or adrenergic chromaffin cells. Transneuronal tracing using pseudorabies virus demonstrated that many, but not all, preganglionic neurons in the vasoconstrictor pathway to forelimb skeletal muscle were CART immunoreactive. Similarly, analysis with the confocal microscope confirmed that 70% of boutons in contact with vasoconstrictor ganglion cells contained CART, whereas 30% did not. Finally, we show that CART-immunoreactive cells represented 69% of the preganglionic neuron population expressing c-Fos after systemic hypoxia. We conclude that CART is present in most, although not all, cardiovascular preganglionic neurons but not thoracic preganglionic neurons with non-cardiovascular targets. We suggest that CART immunoreactivity may identify the postulated "accessory" preganglionic neurons, whose actions may amplify vasomotor ganglionic transmission.

Generating diversity: Mechanisms regulating the differentiation of autonomic neuron phenotypes

Sympathetic and parasympathetic postganglionic neurons innervate a wide range of target tissues. The subpopulation of neurons innervating each target tissue can express unique combinations of neurotransmitters, neuropeptides, ion channels and receptors, which together comprise the chemical phenotype of the neurons. The target-specific chemical phenotype shown by autonomic postganglionic neurons arises during development. In this review, we examine the different mechanisms that generate such a diversity of neuronal phenotypes from the pool of apparently homogenous neural crest progenitor cells that form the sympathetic ganglia. There is evidence that the final chemical phenotype of autonomic postganglionic neurons is generated by both signals at the level of the cell body that trigger cell-autonomous programs, as well as signals from the target tissues they innervate.

Impaired vascular responses to parasympathetic nerve stimulation and muscarinic receptor activation in the submandibular gland in nonobese diabetic mice

Introduction

Decreased vascular responses to salivary gland stimulation are observed in Sjögren's syndrome patients. We investigate whether impaired vascular responses to parasympathetic stimulation and muscarinic receptor activation in salivary glands parallels hyposalivation in an experimental model for Sjögren's syndrome.

Methods

Blood flow responses in the salivary glands were measured by laser Doppler flowmeter. Muscarinic receptor activation was followed by saliva secretion measurements. Nitric oxide synthesis-mediated blood flow responses were studied after administration of a nitric oxide synthase inhibitor. Glandular autonomic nerves and muscarinic 3 receptor distributions were also investigated.

Results

Maximal blood flow responses to parasympathetic stimulation and muscarinic receptor activation were significantly lower in nonobese diabetic (NOD) mice compared with BALB/c mice, coinciding with impaired saliva secretion in nonobese diabetic mice (P < 0.005). Nitric oxide synthase inhibitor had less effect on blood flow responses after parasympathetic nerve stimulation in nonobese diabetic mice compared with BALB/c mice (P < 0.02). In nonobese diabetic mice, salivary gland parasympathetic nerve fibres were absent in areas of focal infiltrates. Muscarinic 3 receptor might be localized in the blood vessel walls of salivary glands.

Conclusions

Impaired vasodilatation in response to parasympathetic nerve stimulation and muscarinic receptor activation may contribute to hyposalivation observed in nonobese diabetic mice. Reduced nitric oxide signalling after parasympathetic nerve stimulation may contribute in part to the impaired blood flow responses. The possibility of muscarinic 3 receptor in the vasculature supports the notion that muscarinic 3 receptor autoantibodies present in nonobese diabetic mice might impair the fluid transport required for salivation. Parasympathetic nerves were absent in areas of focal infiltrates, whereas a normal distribution was found within glandular epithelium.

Trial registration

The trial registration number for the present study is 79-04/BBB, given by the Norwegian State Commission for Laboratory Animals.

Carbachol-induced in vitro secretion of certain human submandibular proteins investigated by mass-spectrometry

OBJECTIVE

To investigate protein content of saliva produced in vitro by samples of human submandibular gland following stimulation with the muscarinic agent carbachol.

DESIGN

Tissue samples, obtained at surgery from seven patients and showing normal morphological appearance, were tested for 30 min: in absence of carbachol and atropine; in presence of carbachol (10 microM); in presence of carbachol (10 microM) and atropine (20 microM); or in presence of just atropine (20 microM). Medium was analysed by high-performance liquid chromatography-mass-spectrometry. Neither before nor during surgery were the patients exposed to drug treatments that were likely to influence the in vitro secretion.

RESULTS

Proline-rich proteins (PRP)-1 and -3, peptide PC and PB, statherin, cystatins SN, S1 and S2 were invariably found in control gland tissue medium. Mean concentrations of these proteins/peptides in the medium were non-proportionally elevated following carbachol exposure to the gland tissues. Difference between basal release and carbachol-induced secretion achieved statistical significance as to all the proteins/peptides under study but for statherin. Atropine alone or atropine plus carbachol caused no significant changes compared to the basal release of proteins/peptides.

CONCLUSIONS

In vitro studies on salivary glands make it possible to study protein secretion from individual glands and thus, to reveal the contribution of the various types of gland to protein/peptide content of whole saliva. The disproportional responses to carbachol may imply that the proteins/peptides are not confined to the same cells or to the same intracellular locations and are therefore not secreted as packages at parasympathetic cholinergic activity.

Role of capsaicin-sensitive sensory nerves in mediation of the cardiovascular effects of the essential oil of croton zehntneri leaves in anaesthetized rats

The essential oil of Croton zehntneri Pax et Hoffm. (EOCZ) contains anethole (42%) and estragole (46%), two isomers that share some chemical structural similarities with capsaicin. The present study investigated the cardiovascular effects of EOCZ and the role of capsaicin-sensitive sensory nerve fibres in the mediation of these effects in anaesthetized rats. 2. Intravenous bolus injection of EOCZ (1-20 mg/kg) elicited dose-dependent hypotension and bradycardia that were immediate and transient. Similar responses were also observed with anethole and estragole (both at 10 mg/kg). After cervical bivagotomy or perineural treatment of both cervical vagus nerves with capsaicin (250 mg/mL) to selectively block the conduction of sensory C-fibres, both cardiovascular responses to EOCZ (10 mg/kg) were abolished. 3. Like capsaicin, an epigastric retrograde intra-arterial injection of EOCZ (10 mg/kg, i.a.) into the femoral artery elicited a monophasic hypotensive response. This reflex response was blocked by either neonatal pretreatment with capsaicin (50 mg/kg, s.c.) or intrathecal injection of the substance P receptor antagonist RP 67580 (7.8 nmol, at the spinal level L5-L6), suggesting that it is mediated exclusively by substance P-containing primary afferent fibres. 4. The cardiovascular responses to EOCZ (10 mg/kg, i.v.) were also significantly reduced by the selective vallinoid TPRV1 receptor antagonist capsazepine (1 mg/kg, i.v.). 5. It is concluded that i.v. administration of EOCZ in anaesthetized rats elicits a capsaicin-like bradycardic and depressor reflex, which appears to be mediated by the activation of vallinoid TPRV1 receptors located on vagal sensory nerves. Like capsaicin, i.a. injection of EOCZ induces a spinally mediated sensory reflex.

Parasympathetic nerve-evoked protein synthesis, mitotic activity and salivary secretion in the rat parotid gland and the dependence on NO-generation

Incorporation of radiolabelled leucine and thymidine into trichloroacetic acid-insoluble material of the parotid gland was used as indices of protein synthesis and mitotic activity, respectively, following electrical stimulation of the parasympathetic auriculo-temporal nerve for 30 min in pentobarbitone-anaesthetized rats under adrenoceptor blockade (phentolamine and propranolol, 2mg/kg intravenous of each) in the absence or presence of atropine (2mg/kg intravenous) and without or with nitric oxide synthase inhibitors. In atropinized rats, the parasympathetic non-adrenergic, non-cholinergic (NANC) nerve-evoked mean increases in protein synthesis at a frequency of 10 Hz (142%) and 40 Hz (200%) were not affected in a statistically significant way (124 and 275%, respectively) by the neuronal type NO-synthase inhibitor N(w)propyl-l-arginine (N-PLA) (30 mg/kg intravenous). Neither were the increase (175%) in protein synthesis at 10 Hz in non-atropinized animals affected by N-PLA (180%). The increase (65%) in mitotic activity, 19 h after the end of stimulation at 40 Hz, in the presence of atropine, was not affected by N-PLA (55%). Neither were the increase (95%) in gland content of amylase at this point of observation statistically significant affected by N-PLA (144%). The secretion of fluid and output of amylase from the parotid gland upon nerve stimulation was not affected by N-PLA. When examining the non-selective NO-synthase inhibitor l-NAME (30 mg/kg intravenous) in atropinized rats subjected to stimulation at 10 Hz, neither the increase in protein synthesis nor the evoked fluid response or amylase outputs were affected. Hence, in contrast to an NO-dependent sympathetic-induced protein synthesis and mitosis in the parotid gland, involving the activity of the neuronal type NO-synthase, no support for a parasympathetic-induced protein synthesis (and gain in gland amylase) and mitosis, depending on NO-generation, was found. Likewise, the present findings provide no evidence for a role of NO in the parasym pathetic nerve-evoked fluid secretion and amylase output.

Distribution of neuropeptide Y Y1 receptors in rodent peripheral tissues

Using a sensitive immunohistochemical technique, the localization of neuropeptide Y (NPY) Y1-receptor (Y1R)-like immunoreactivity (LI) was studied in various peripheral tissues of rat. Wild-type (WT) and Y1R-knockout (KO) mice were also analyzed. Y1R-LI was found in small arteries and arterioles in many tissues, with particularly high levels in the thyroid and parathyroid glands. In the thyroid gland, Y1R-LI was seen in blood vessel walls lacking alpha-smooth muscle actin, i.e., perhaps in endothelial cells of capillaries. Larger arteries lacked detectable Y1R-LI. A distinct Y1R-immunoreactive (IR) reticulum was seen in the WT mouse spleen, but not in Y1R-KO mouse or rat. In the gastrointestinal tract, Y1R-positive neurons were observed in the myenteric plexus, and a few enteroendocrine cells were Y1R-IR. Some cells in islets of Langerhans in the pancreas were Y1R-positive, and double immunostaining showed coexistence with somatostatin in D-cells. In the urogenital tract, Y1R-LI was observed in the collecting tubule cells of the renal papillae and in some epithelial cells of the seminal vesicle. Some chromaffin cells of adrenal medulla were positive for Y1R. The problem of the specificity of the Y1R-LI is evaluated using adsorption tests as well as comparisons among rat, WT mouse, and mouse with deleted Y1R. Our findings support many earlier studies based on other methodologies, showing that Y1Rs on smooth muscle cells of blood vessels mediate NPY-induced vasoconstriction in various organs. In addition, Y1Rs in other cells in parenchymal tissues of several organs suggest nonvascular effects of NPY via the Y1R.

Enhancement of salivary secretion and neuropeptide (substance P, alpha-calcitonin gene-related peptide) levels in saliva by chronic anethole trithione treatment

Anethole trithione, a choleretic, has been reported to be effective in the treatment of dry mouth. We have examined the effects of chronic treatment with anethole trithione on salivary secretion, substance P immunoreactive substance (SP-IS) and alpha-calcitonin gene-related peptide immunoreactive substance (alpha-CGRP-IS) concentrations in human saliva. Anethole trithione caused significant increases of saliva SP-IS concentrations from the day 13 (25.3 +/- 1.6 pg mL(-1)) to day 14 (25.8 +/- 1.7 pg mL(-1)) compared with day 1 (19.9 +/- 1.9 pg mL(-1)). Anethole trithione caused significant increase in saliva alpha-CGRP-IS concentration on day 14 (39.9 +/- 4.7 pg mL(-1)) compared with day 1 (27.7 +/- 4.7 pg mL(-1)). Anethole trithione significantly increased the sialosis volumes from day 11 to day 14 (1.6 +/- 0.1-1.7 +/- 0.2 mL) compared with the day 1 (1.2 +/- 0.2 mL). Simple linear regression of the increase in sialosis volume with saliva SP-IS (r = 0.94) and alpha-CGRP-IS (r = 0.97) concentrations was found. These results demonstrated that chronic treatment with anethole trithione affected saliva SP-IS and alpha-CGRP-IS concentration in human saliva and sialosis volume.

Autonomic regulation of cystatin S gene expression in rat submandibular glands

Innervation of rat submandibular and parotid glands by the autonomic nervous system regulates saliva volume, its rate of secretion and its composition. The autonomic nervous system also plays a regulatory role in the differentiation and growth of salivary glands, and in the expression of specific sets of genes. Rat cystatin S, a member of family 2 of the cysteine proteinase inhibitor superfamily, is expressed in submandibular and parotid glands of human and rat. In the rat, cystatin S gene expression is tissue- and cell type-specific, is temporally regulated during postnatal development, and not observed in adult animals. The beta-adrenergic agonist isoproterenol (IPR) induces hypertrophic and hyperplastic enlargements of rat salivary glands and the expression of a number of genes including cystatin S. Sympathectomy reduces, but does not completely block, IPR-induced expression of the cystatin S gene in submandibular glands of adult female rats, indicating the participation of sympathetic factor(s) in its regulation. Bilateral parasympathectomy also reduces IPR-induced cystatin S gene expression, suggesting a role of the parasympathetic nervous system in its regulation. Experiments described in this paper suggest that similar factor(s) arising from both the sympathetic and parasympathetic branches of the autonomic nervous system simultaneously participate in IPR-induced cystatin S gene expression in submandibular glands.

The protein composition of ferret parotid saliva as revealed by high-resolution electrophoretic methods

Ferret parotid saliva has been analysed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis (2-DE) to determine, for the first time, its protein composition. SDS-PAGE, in combination with Coomassie Brilliant Blue (CBB) staining, revealed up to 20 bands and the patterns were characterised by major protein constituents of Mr 105000, 51000, 47000, 33000, 22000 and 16 400 common to all samples from all animals. Sequential samples collected from the same animal during prolonged stimulation of the parasympathetic nerve (40 min at 40 Hz) showed subtle but reproducible protein changes. Saliva collected from different animals varied widely in the amount of a protein Mr 66000. 2-DE, in combination with silver staining, revealed up to 300 spots and the patterns were characterised by major protein constituents of Mr 105000 (pI 6.3-7.2), Mr 66000 (pI 4.7-5.3), Mr 51000 (pI 5.0-5.7), Mr 47000 (pI 6.0-7.5), and Mr 33000 (pI 4.7-6.0). Many of the polypeptide spot clusters consisted of one or more horizontal strings of spots suggesting extensive microheterogeneity. Both SDS-PAGE and 2-DE indicated that the protein patterns of ferret parotid saliva evoked by electrical stimulation of the parasympathetic nerve in the absence or presence of atropine are similar, i.e., the protein composition of the atropine-resistant nonadrenergic, noncholinergic (NANC) secretion is similar to that of saliva evoked in the absence of muscarinic receptor blockade.

NPY/sympathetic and NPY/VIP innervation of the blood vessels supplying rat tooth-related structures: effects of sympathectomy

In order to better understand the regulation of blood flow to tooth-related structures, the patterns of VIP- and NPY-ergic innervations in the rat were examined. Nerve fibers showing NPY-like immunoreactivity (NPY-LI) frequently occurred in the walls of the large main arteries, as well as in association with the arterioles, to a high degree co-existing with tyrosine hydroxylase (TH), whereas VIP-LI was mainly restricted to the walls of the large arteries. After sympathectomy, no NPY/TH-LI nerve fibers were seen in blood vessel walls. However, a NPY-immunoreactive nerve population remained in the walls of the large arteries, NPY- and VIP-LI co-existing in this nerve population. Both immunoreactions were intense. The present study suggests that a NPY/sympathetic innervation as well as a VIP innervation (large arteries) are likely to have substantial roles in the balance and maintenance of vasoregulation in tooth-related structures and that a NPY/VIP innervation becomes of particular importance when the NPY/sympathetic innervation is destroyed.

High-resolution electrophoretic analysis of rat parotid salivary proteins

Silver staining and high-resolution electrophoretic methods have been used to compare the protein composition of rat parotid saliva evoked in response to (i) parasympathetic stimulation (including the nonadrenergic, noncholinergic, atropine-associated secretion), (ii) sympathetic stimulation, or (iii) the infusion of neuropeptides with secretagogue activity (substance P, calcitonin gene-related peptide, neuropeptide Y, or vasoactive intestinal peptide). The different stimuli influenced the protein concentration and flow rate of the evoked secretion but had little effect upon the protein composition of the saliva. In contrast to earlier studies using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Coomassie blue staining, the combination of silver staining and two-dimensional electrophoresis (2-DE) revealed many newly detected proteins. The results indicate that the protein composition of rat parotid saliva is more complex than previously reported but is unaffected by the mode of stimulation.

Isoproterenol-induced expression of the cystatin S gene in submandibular glands of parasympathectomized rats

Parasympathetic innervation of rat submandibular and parotid glands regulates saliva volume, its rate of secretion and its composition. It also has a regulatory role in hypertrophy and hyperplasia of salivary glands, and in the expression of specific sets of genes. Rat cystatin S is a member of family 2 of the cysteine proteinase inhibitor superfamily. Cystatin S gene expression is tissue- and cell type-specific, temporally regulated during postnatal development, and not observed in adult animals. Isoproterenol (IPR), a beta-adrenergic agonist, induces hypertrophic and hyperplastic enlargement of rat salivary glands and expression of a number of genes including cystatin S. Sympathectomy reduces, but does not completely block IPR-induced expression of the cystatin S gene in the submandibular glands of adult female rats, indicating the participation of sympathetic factor(s) in this regulation. Since both sympathetic and parasympathetic branches of the autonomic nervous system act in parallel in the submandibular gland, it is possible that parasympathetic nerve terminals also provide factor(s) that play a role in regulation of cystatin S gene expression. Experiments described in this paper were designed to test the hypothesis that the parasympathetic nervous system participates in IPR-induced cystatin S gene expression. Bilateral parasympathectomy reduced IPR-induced cystatin S gene expression, suggesting a role of the parasympathetic nervous system in its regulation. Unilateral parasympathectomy in contrast, had no effect on IPR-induced cystatin S gene expression, suggesting that the presence of an intact parasympathetic innervation in the contralateral side permits the 'normal' IPR-induced expression of the cystatin S gene in the parasympathectomized gland.

Nitric oxide synthase immunoreactive nerves in rat and ferret salivary glands, and effects of denervation

Nitric oxide has been implicated in mechanisms mediating nerve-evoked vasodilatory and secretory responses in salivary glands. In the present study, the occurrence and distribution of nitric oxide synthase (NOS)-immunoreactive nerves in ferret and rat salivary glands were investigated using immunocytochemistry with rabbit and sheep NOS antisera, and using NADPH-diaphorase enzyme histochemistry. In the parotid, submandibular and sublingual glands of the rat and the ferret, NOS-immunoreactive varicose terminals encircled acini and arteries of various sizes. In the ferret, collecting ducts were also supplied with NOS-immunoreactive fibres. In the rat, only the granular ducts of the submandibular gland were supplied with such fibres. The NOS-immunoreactive innervation of acinar cells was more abundant in the rat than in the ferret, whereas the opposite was true for the innervation of blood vessels. No NOS immunoreactivity was observed in the vascular endothelium. In both species, NOS-positive ganglionic cell bodies were found in the hilar regions of the submandibular and sublingual glands, whereas none could be detected in the parotid glands. NADPH-diaphorase reactivity had the same neuronal distribution as NOS immunoreactivity and, in addition, NADPH-diaphorase reactivity was expressed in ductal epithelium. Neither sympathetic denervation (by removal of the superior cervical ganglion) nor treatment with the sensory neurotoxin capsaicin reduced the NOS-immunoreactive innervation of the parotid gland. However, parasympathetic denervation (by cutting the auriculo-temporal nerve) caused an almost total disappearance of the NOS-immunoreactive innervation. The present findings provide a morphological background to the suggested role of nitric oxide in parasympathetic secretory and vascular responses of salivary glands.

Neuropeptide-containing nerve fibres in the human parotid gland: a semiquantitative analysis using an antibody against protein gene product 9.5

The occurrence and distribution of neuropeptide-containing fibres in the human parotid gland were examined by the peroxidase-antiperoxidase method with attention to the quality of fixation and the condition of patients. Many fibres immunoreactive for neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) and a moderate number of galanin-positive (GAL) fibres were distributed around the acini. A moderate number of NPY and VIP fibres were distributed around the intercalated ducts. The semiquantitative mean densities (+/- SD) of periacinar NPY, VIP and GAL fibres expressed as a percentage of the total protein gene product (PGP) 9.5 immunoreactive fibres were 75.62 +/- 7.25%, 70.52 +/- 9.33% and 41.76 +/- 5.45%, respectively, whereas those of substance P (SP), calcitonin gene-related peptide (CGRP) and FMRF amide (FMRF) fibres were below 10%. The mean densities of NPY and VIP fibres around the intercalated ducts expressed as the percentage of PGP 9.5 fibres associated with these ducts were 52.37 +/- 6.19% and 59.62 +/- 7.02% respectively. Those of SP, CGRP, GAL, and FMRF fibres were below 10%. The densities of NPY, VIP, SP, CGRP, GAL and FMRF fibres around the striated and excretory ducts were also below 10%. In the vasculature, NPY fibres were the most prominent. Similarly, the mean density of perivascular NPY fibres was 93.76 +/- 2.03%. No somatostatin or leucine or methionine enkephalin immunoreactivity was detected around the acini, duct system or blood vessels. These findings suggest that, in this gland, the periacinar NPY, VIP and GAL fibres may participate in regulating the synthesis of saliva and its secretion and that perivascular peptidergic fibres, especially NPY fibres, may be involved in controlling local blood flow.

Expression of vasoactive intestinal polypeptide receptor mRNA and secretory regulation by vasoactive intestinal polypeptide in rat submandibular and sublingual salivary glands

Vasoactive intestinal polypeptide (VIP)-receptor mRNA was strongly expressed in the acinar cells in the submandibular gland but not in the sublingual gland. VIP-containing nerve fibres were richly distributed around acini in the submandibular gland but were rare around acini of the sublingual gland. In the submandibular gland, the chorda was stimulated at various frequencies (1-40 Hz) together with an infusion of (N-Ac-Tyr1, D-Phe2)-GRF(1-29)-NH2 (109 M), VIP antagonist, which reduced salivary flow from the submandibular gland only at high-frequency stimulation (> 20 Hz), and more markedly reduced the salivary protein concentration. When the chorda was continuously stimulated the antagonist reduced the salivary flow only during the initial 5 min. Exogenous VIP 10(-12) - 10(-8) M) infusion at the same time as chorda stimulation caused no increase in salivary flow, but the salivary protein concentration was increased in a dose-dependent manner. In the sublingual gland, neither VIP nor the VIP antagonist affected chorda-evoked salivary flow and protein concentration. Thus, endogenous VIP may play a part in the regulation of both fluid and protein secretion, especially of protein, evoked by chorda stimulation at high frequency in the submandibular gland. These phenomena occurred only in the initial phase of secretion. In the sublingual gland, it seems likely that VIP plays no part in the regulatory mechanism, at least with regard to salivary fluid secretion in the acinar cells.