Substance P and neurokinin A immunoreactive nerve fibres in the developing salivary glands of the rat

Regulation of salivary gland function by autonomic nerves

Oral homeostasis is dependent upon saliva and its content of proteins. Reflex salivary flow occurs at a low 'resting' rate and for short periods of the day more intense taste or chewing stimuli evoke up to ten fold increases in salivation. The secretion of salivary fluid and proteins is controlled by autonomic nerves. All salivary glands are supplied by cholinergic parasympathetic nerves which release acetylcholine that binds to M3 and (to a lesser extent) M1 muscarinic receptors, evoking the secretion of saliva by acinar cells in the endpieces of the salivary gland ductal tree. Most salivary glands also receive a variable innervation from sympathetic nerves which released noradrenaline from which tends to evoke greater release of stored proteins, mostly from acinar cells but also ductal cells. There is some 'cross-talk' between the calcium and cyclic AMP intracellular pathways coupling autonomic stimulation to secretion and salivary protein secretion is augmented during combined stimulation. Other non-adrenergic, non-cholinergic neuropeptides released from autonomic nerves evoke salivary gland secretion and parasympathetically derived vasointestinal peptide, acting through endothelial cell derived nitric oxide, plays a role in the reflex vasodilatation that accompanies secretion. Neuronal type, calcium-activated, soluble nitric oxide within salivary cells appears to play a role in mediating salivary protein secretion in response to autonomimetics. Fluid secretion by salivary glands involves aquaporin 5 and the extent to which the expression of aquaporin 5 on apical acinar cell membranes is upregulated by cholinomimetics remains uncertain. Extended periods of autonomic denervation, liquid diet feeding (reduced reflex stimulation) or duct ligation cause salivary gland atrophy. The latter two are reversible, demonstrating that glands can regenerate provided that the autonomic innervation remains intact. The mechanisms by which nerves integrate with salivary cells during regeneration or during salivary gland development remain to be elucidated.

Role of nerve growth factor in the regulation of parotid cell differentiation induced by rat serum

The present study was undertaken to examine the factors that regulate rat serum (RS)- and nerve growth factor (NGF)-induced differentiation in a rat parotid acinar cell line. RS elicited extracellular signal-regulated kinase (ERK1/ERK2) activation within 5min, while cyclic AMP (cAMP) levels transiently rose after 6hr. RS also elicited a rise in amylase mRNA levels within 30min, which preceded the rise in amylase protein levels. A possible role for NGF was suggested by the findings that parotid cells express both TrkA and p75 receptors. The immunoreactivity of these NGF receptors was reduced during exposure to RS. Following prolonged incubation in RS when ERK activity subsided to near basal levels, NGF restored ERK1/ERK2 activity to the elevated level initially observed in RS. NGF was ineffective when cells were incubated in fetal bovine serum. NGF, when incubated in combination with the cAMP-generating neuropeptides, calcitonin gene-related peptide and vasoactive intestinal peptide, markedly enhanced the cellular amylase content produced by RS. We conclude that parotid cell differentiation arises from an activation of cell surface receptors by humoral factors in combination with NGF and cAMP-generating neuropeptides.

Immunochemical analysis of laminin during postnatal development of the rat submandibular gland

Anti-laminin serum was used to investigate distribution patterns and chain composition of laminin during postnatal development of rat submandibular gland. Immunohistochemical analysis showed that in glands of newborn rats laminin was not uniformly present around growing acini. Staining was frequently weak or absent in clefts formed between adjacent cells. This irregular staining pattern decreased progressively over the subsequent periods, and in 30-day-old animals immunoreactivity was observed only at the periphery of glands. Immunoblot analysis showed that laminin was composed of bands corresponding to the alpha 1, beta 1 and gamma 1 polypeptides. The correlation between the pattern of laminin expression and gland maturation suggests a role of laminin in the functional maturation of acinar cells.

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.

Vascular protein leakage in the rat parotid gland elicited by reflex stimulation, parasympathetic nerve stimulation and administration of neuropeptides

Evans blue accumulated in parotid glands of conscious rats in response to feeding (over 60 min), in the absence of atropine and adrenoceptor antagonists and in their presence, and after pretreatment with the sensory neurotoxin capsaicin. Stimulation of the auriculo-temporal nerve (40 Hz, 10 or 20 min), without and with the blockers, caused Evans blue to accumulate. A periglandular oedema also contained the dye. Administration (i.v.) of neurokinin A accumulated Evans blue, while substance P, vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating peptide (PACAP), calcitonin gene-related peptide (CGRP) and pilocarpine lacked effect. Pilocarpine enhanced the action of neurokinin A and, furthermore, substance P combined with either VIP, PACAP or CGRP resulted in accumulation of Evans blue. In the sublingual + submandibular glands, Evans blue increased in response to neurokinin A and pilocarpine; furthermore, substance P and VIP, and substance P and CGRP, interacted positively. Bradykinin lacked effect in the glands. Comparisons were made with the urinary bladder. Accumulation of Evans blue reflects plasma protein extravasation. In salivary glands, the phenomenon occurred during feeding and was independent on intact sensory innervation; instead, the parasympathetic innervation containing the neuropeptides was in focus. In the clinic, the present findings may have implications for the aetiology of gland swelling and pain.

Rat serum induces a differentiated phenotype in a rat parotid acinar cell line

To establish a continuous cell line, freshly prepared rat parotid acinar cells were stably transfected with a plasmid vector containing the SV40 large T antigen. The acinar origin of these cells was confirmed by Western blotting, enzyme analysis, and morphological analysis. Transformed cells grown in 10% rat serum showed a modest reduction in cell number after 7 days and a concentration- and time-dependent increase in amylase levels approximately 16 times greater than those observed in fetal bovine serum-treated cells. Ultrastructural analysis revealed that cells grown in rat serum harbored protein-filled secretory granules localized adjacent to the endoplasmic reticulum, and punctate amylase-specific immunofluorescence distributed throughout the cytoplasm was consistent with the presence of amylase in secretory organelles. Clonal cells express tissue-specific proline-rich proteins and the four protein kinase C isozymes present in primary culture. Carbachol and isoproterenol stimulated [3H]protein secretion and isoproterenol enhanced amylase secretion from cells grown in rat serum. Moreover, norepinephrine, carbachol, and substance P produced a time- and concentration-dependent rise in cytoplasmic Ca2+. This continuous cell line of parotid acinar cells, which after treatment with rat serum retains the basic structural and functional properties of primary culture cells, will be utilized as a model system for studying long-term biological processes that regulate parotid cell function.

Tachykinins in the gut. Part II. Roles in neural excitation, secretion and inflammation

The preprotachykinin-A gene-derived peptides substance (substance P; SP) and neurokinin (NK) A are expressed in intrinsic enteric neurons, which supply all layers of the gut, and extrinsic primary afferent nerve fibers, which innervate primarily the arterial vascular system. The actions of tachykinins on the digestive effector systems are mediated by three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Within the enteric nervous system, SP and NKA are likely to mediate, or comediate, slow synaptic transmission and to modulate neuronal excitability via stimulation of NK3 and NK1 receptors. In the intestinal mucosa, tachykinins cause net secretion of fluid and electrolytes, and it appears as if SP and NKA play a messenger role in intramural secretory reflex pathways. Secretory processes in the salivary glands and pancreas are likewise influenced by tachykinins. The gastrointestinal arterial system may be dilated or constricted by tachykinins, whereas constriction and an increase in the vascular permeability are the only effects seen in the venous system. Various gastrointestinal disorders are associated with distinct changes in the tachykinin system, and there is increasing evidence that tachykinins participate in the hypersecretory, vascular and immunological disturbances associated with infection and inflammatory bowel disease. In a therapeutic perspective, it would seem conceivable that tachykinin antagonists could be exploited as antidiarrheal, antiinflammatory and antinociceptive drugs.

Ontogeny of the peptidergic fibers in the male mouse submandibular gland

The first appearance of substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), galanin (GAL), leucine-enkephalin (1-ENK), and methionine-enkephalin (m-ENK) in the male mouse submandibular glands were different for each. VIP immunoreactive fibers first appeared on embryonic day 15 (E15), SP on E16, and CGRP fibers on E18. GAL, 1-ENK, and m-ENK fibers appeared in the early postnatal period, and NPY fibers occurred on postnatal day 21 (P21). From P0 to P21, VIP fibers rapidly increased in number, but SP and CGRP fibers increased only slightly. After P21, VIP, SP, and CGRP fibers decreased in number. ENK fibers were found only from P0 to P14. The number of these immunoreactive fibers in the adult phase was low in comparison with that in early postnatal phase. Around the blood vessels, SP, VIP, CGRP, NPY, and GAL fibers appeared by at least P7. These findings suggested that the transient high activity of VIP, CGRP, SP, and GAL and the transient appearance of ENKs in the nerve fibers may be related to the cell proliferation and differentiation of the functionally important structures of the mouse submandibular glands, and that the peptidergic innervation around the vasculature is probably involved in controlling local glandular circulation.

Thermolytic salivation, substance P and kinins in rats

In the heat, rats produce a large flow of saliva that they spread on their fur. We have tested whether substance P (SP) is involved in this response by using RP 67580, a NK1 tachykinin receptor antagonist, in normal and in kininogen-deficient rats. In anaesthetized rats, the sialogogic effect of SP (1 and 5 micrograms.kg-1 iv) was inhibited by RP 67580 (50 to 2500 micrograms.kg-1 iv). SP (5 micrograms.kg-1 iv) did not modify the vascular permeability to 125I-labelled albumin in submaxillary glands but increased this permeability in periglandular soft tissues and in the ears. This effect was suppressed by RP 67580 (50 to 2500 micrograms.kg-1 ip). Unanaesthetized normal male Wistar rats were exposed to ambient temperatures of 26 degrees C (thermoneutral range) or 36 degrees C for one hour. After this time period, a loss of body weight was observed. The thermolytic water loss reached 2% of body weight. This body weight loss was reduced by atropine (3 mg.kg-1 ip) or RP 67580 (50 to 2500 micrograms.kg-1 ip). The submaxillary glands were swollen and accumulated labelled albumin. This accumulation was reduced by atropine but was not affected by RP 67580. An extravasation of labelled albumin occurred in periglandular tissues. This accumulation was not modified by atropine which induced a large oedema of the soft tissues. Protein extravasation was suppressed by RP 67580 (2500 micrograms.kg-1) which did not modify or increased the volume of the oedema.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P (SP) and neurokinin A (NKA) in developing submandibular glands of the rat

The effect of isoprenaline, carbachol, substance P (SP) and neurokinin A (NKA) on peroxidase and total protein secretion was studied in the developing postnatal submandibular glands of the rat using in vitro methods. Submandibular glands of 1, 5, 12 and 30 day-old rats were stimulated by 10(-5) M isoprenaline and carbachol, and 10(-6) M SP and NKA. The stimulatory effects of these compounds were compared to the basic release of peroxidase and total amount of protein from submandibular gland fragments in incubation solution with no added transmitter substances. Indirect immunohistochemical methods were used to study these developing glands from SP- and NKA-immunoreactive (IR) nerve fibers. The distributions of SP-IR and NKA-IR nerve fibers closely resembled each other, being most abundantly spread around the developing acini and ducts. The number of these fibers was high on the 1st, 5th and 12th days, but was decreased on the 30th day. On peroxidase release, isoprenaline was the most effective, causing a maximal response of 47 times the basic release on the first postnatal day, after which it gradually decreased. The effects of carbachol, SP and NKA on peroxidase release were clearly weaker and, unlike isoprenaline, their strongest response was on the 5th postnatal day (carbachol, 4.3; SP 5.2; NKA, 4.5). The total protein secretion effect patterns of the studied substances resembled each other more, showing their strongest response on the 5th day (isoprenaline, 5.0; carbachol, 4.5; SP, 4.2; NKA, 3.4) and decreasing thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Kallikrein, nitric oxide and the vascular responses of the submaxillary glands in rats exposed to heat

During exposure of normal rats to an ambient temperature of 36 degrees C or 40 degrees C, body temperature increases; thermolytic processes are set up and saliva is spread on the skin. In Wistar rats, thermolytic salivation started when body temperature was above 39 degrees C. This water loss was associated with a loss of body weight. A 10% reduction of plasma volume was observed in animals exposed to 40 degrees C but no change was observed in those exposed to 36 degrees C. Body weight loss was reduced by hexamethonium, atropine, prazosin, HOE 140, a bradykinin-antagonist, and NG-nitro-L-arginine (NOARG), a NO synthase inhibitor. The weight and blood content of the submaxillary glands, which are the main effectors of the thermolytic processes, increased as a function of the ambient temperature. The increase of blood content was enhanced by hexamethonium but reduced by atropine and NOARG. The weight increase was inhibited by hexamethonium, prazosin, HOE 140 and NOARG. At an ambient temperature of 40 degrees C, a large swelling developed around the submaxillary glands, resulting in a distention of the surrounding soft tissues. This local oedema fluid contained low levels of endogenous proteins but accumulated exogenous labelled albumin. This swelling was enhanced by atropine but decreased by hexamethonium, trasylol, HOE 140, NOARG, ketoprofen, a cyclooxygenase inhibitor, and prazosin. In kininogen deficient rats, the blood content of submaxillary glands increased as a function of ambient temperature. No increase in glandular weight and no swelling of the of the soft tissues were observed. After atropine, the weight of the glands increased and a swelling of the soft tissues appeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of substance P and neurokinin A immunoreactivity in ganglia supplying nerves to the submandibular glands of the rat

Developing submandibular, trigeminal and superior cervical ganglia, which provide innervation to the submandibular glands, were studied for substance P (SP)- and neurokinin A (NKA)-immunoreactive (IR) ganglion cells and nerve fibres in rat. These ganglia were examined by using an indirect immunofluorescence technique at daily intervals from the 16th day in utero (i.u.) until birth, and subsequently on the 2nd, 5th, 7th, 12th, 16th, 30th, 42nd postnatal day and in the adult (3 months). In the submandibular ganglion SP- and NKA-IR cells and fibres first appeared in considerable numbers on the 19th day i.u. (in one sample out of five on the 18th day i.u.), when more than 90% of the ganglion cells were immunoreactive to SP and NKA. The number stayed at more than 90% to the 7th postnatal day and then slowly decreased to the levels of adult animals (18% SP, 17% NKA). The first SP- and NKA-IR ganglion cells and fibres appeared in the trigeminal ganglion on the 18th day i.u. when they represented 7% (SP) and 4% (NKA) of the ganglion cells. The number of SP- and NKA-IR cells increased steadily, reaching a maximum at the time of birth when 68% (SP) and 74% (NKA) of the ganglion cells were immunoreactive. Thereafter they began to decrease toward the level of an adult rat (10% SP, 11% NKA). In the superior cervical ganglion only a few SP- and NKA-IR ganglion cells were detected from the 19th day i.u. to the fifth postnatal day. Positive ganglion cells were also occasionally found in the nerve trunks outside the superior cervical ganglion.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcitonin gene-related peptide immunoreactive nerve fibers in the developing salivary glands of the rat

The appearance and distribution of calcitonin gene-related peptide immunoreactive (CGRP-IR) nerve fibers was studied by indirect immunofluorescence microscopy in the developing salivary glands of the rat at daily age intervals from the 15th day in utero (i.u.) until birth, and subsequently on the 2nd, 5th, 7th, 16th, 30th postnatal (p.n.) days. The findings were compared to samples of adult rats. CGRP-IR fibers appeared on day 20 i.u. both in parotid and submandibular glands. In submandibular glands, fibers were first seen surrounding the developing ductal branches, in the mesenchyme and also in association with developing ducts and blood vessels. In the parotid gland CGRP-IR fibers first appeared around ductal branches and blood vessels on day 20 i.u. and on day 21 i.u. CGRP-IR nerve fibers were found in the mesenchyme and around developing ducts. The density of CGRP-IR fibers was highest between the 2nd and 16th postnatal days, after which the amount of CGRP immunoreactivity slowly decreased to the levels of adult glands. The increase in a number of CGRP-IR nerve fibers especially around the ductal and vascular elements in the developing salivary glands indicates that they may play a role in the functional maturation of salivary glands.

Substance P and neurokinin A immunoreactive nerve fibres in the developing salivary glands of the rat

The time of appearance and distribution of substance P (SP) and neurokinin A (NKA) immunoreactive nerve fibres in developing salivary glands of the rat were studied by the use of indirect immunohistochemical methods. The glands were examined at daily intervals from the 15th day in utero (i.u.) until birth, and subsequently on the 2nd, 5th, 7th, 12th, 16th and 30th postnatal day. The findings were compared to samples from adult. The first SP- and NKA-immunoreactive (IR) nerve fibres appeared on the 19th day i.u. in the parotid and submandibular glands and were abundantly distributed around developing ductal branches. In the mesenchyme around the developing ductal branches of the parotid gland the fibres appeared on the 20th day i.u. In the submandibular gland NKA-IR fibres appeared in the mesenchyme surrounding the developing ductal branches on the 19th day i.u. and SP-IR fibres on the 21st day i.u. Around blood vessels of both glands, SP- and NKA-IR fibres made their appearance only much later, on the second postnatal day. The number of SP- and NKA-IR nerve fibres in the developing salivary glands was already high on the 19th day i.u. when they were first detected. From this point up to the 16th postnatal day the glands were richly innervated by the fibres, but later the numbers slowly decreased to adult levels. The abundance of SP- and NKA-IR nerve fibres especially around the ductal branches and secretory structures in the developing salivary glands suggests a role in the functional maturation of salivary glands.