Salivary secretion induced by substance P

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.

The Mouse Parotid Gland Preparation: An in vivo Pharmacological Tool

The effects of several autonomic agents on total protein, amylase, RNase, calcium, potassium, and sodium levels and also on flow rate of mouse parotid saliva were investigated during the process of evaluating the in vivo mouse parotid gland preparation as a pharmacological tool. Acetylcholine and pilocarpine were used as secretagogues and produced different sequential patterns of sodium and enzyme levels secreted in mouse parotid saliva. Additionally, propranolol treatment was able to alter amylase and sodium levels produced by pilocarpine stimulation significantly, as well as alter calcium levels produced by both acetylcholine and pilocarpine stimulation. Phentolamine treatment resulted in higher amylase levels with both acetylcholine and pilocarpine stimulation. The use of acetylcholine as a secretagogue allows one to perform in vivo anticholinergic experiments which alter flow rates without significantly altering protein or ion levels secreted in mouse parotid saliva.

Effects of calcitonin and calcitonin gene-related peptide on the substance P-mediated secretion of fluid from the rat submandibular gland

1. The effects of rat calcitonin gene-related peptide (rCGRP), rat calcitonin (rCT) and salmon calcitonin (sCT) on the substance P-mediated (SP-mediated) secretion of fluid from the rat submandibular gland were investigated. 2. Rat CGRP potentiated and prolonged the SP-mediated secretion of fluid from the rat submandibular gland in a dose-dependent manner. CGRP also enhanced methacholine- and phenylephrine-mediated secretion of fluid. 3. The potentiating effect of the combination of rCGRP and SP was somewhat reduced by pretreatment with spantide, human CGRP8-37 and atropine but not by pretreatment with phentolamine or with propranolol. 4. Salmon CT at a low dose mimicked the effect of rCGRP on the SP-mediated secretion of fluid, but its potency was lower than that of rCGRP. However, rCT had no effect on the SP-mediated secretion of fluid. 5. These results suggest that the potentiating effects of rCGRP and SP might involve cholinergic receptors, as well as CGRP and tachykinin receptors, and that sCT, but not rCT, is able to mimic rCGRP in potentiating the secretion of fluid induced by SP.

Protein secretion from rat submandibular acini and granular ducts: effects of exogenous VIP and substance P during parasympathetic nerve stimulation

The influences of exogenous vasoactive intestinal peptide (VIP) and substance P on the release of peroxidase from acini and true tissue kallikrein (rK1) from granular ducts of the rat submandibular gland were studied during continuous parasympathetic stimulation. Parasympathetic nerve impulses caused a moderate flow of saliva (mean +/- SD, 108+/-26 microl/g tissue/min) that had a low protein concentration (174+/-88 microg/ml). The outputs of peroxidase and rK1 were minimal (14.3+/-11.8 pmol DCF/g tissue/min and 6.5+/-3.4 nmol AFC/g tissue/min, respectively). When administered intravenously, VIP had no apparent effect on the overall flow rate, but caused a significant increase in the output of peroxidase; 450% at 1 microg/kg and a further 10-fold increase at 10 microg/kg. In contrast, substance P (1 microg/kg) evoked a marked increase in flow rate (68%), and peroxidase secretion increased only 3-fold. The output of rK1 was unaffected by either VIP or substance P. Our results support the hypothesis that acinar, but not granular duct, protein secretion is evoked by non-adrenergic, non-cholinergic peptides released from parasympathetic nerve terminals.

Exocrine gland dysfunction in MC5-R-deficient mice: evidence for coordinated regulation of exocrine gland function by melanocortin peptides

The effects of pituitary-derived melanocortin peptides are primarily attributed to ACTH-mediated adrenocortical glucocorticoid production. Identification of a widely distributed receptor for ACTH/MSH peptides, the melanocortin-5 receptor (MC5-R), suggested non-steroidally mediated systemic effects of these peptides. Targeted disruption of the MC5-R produced mice with a severe defect in water repulsion and thermoregulation due to decreased production of sebaceous lipids. High levels of MC5-R was found in multiple exocrine tissues, including Harderian, preputial, lacrimal, and sebaceous glands, and was also shown to be required for production and stress-regulated synthesis of porphyrins by the Harderian gland and ACTH/MSH-regulated protein secretion by the lacrimal gland. These data show a requirement for the MC5-R in multiple exocrine glands for the production of numerous products, indicative of a coordinated system for regulation of exocrine gland function by melanocortin peptides.

Effect of substance P and receptor antagonists on secretion of lingual lipase and amylase from rat von Ebner's gland

Substance P (SP, 1 microM) when incubated with minced von Ebner's glands for 15, 30, and 60 min, stimulated secretion of lingual lipase (12.14% +/- 0.90) and amylase (8.30% +/- 0.42). Only 10 microM of the SP receptor antagonist CP-96,345 significantly inhibited SP-evoked secretion. D-Pro2-D-Phe7-D-Trp9-SP (Ia), D-Pro2-D-Trp7,9-SP (Ib), D-Arg1-D-Trp7,9-D-Leu11-SP (Ic), or 1 microM CP-96,345 were not effective, suggesting that the SP receptor of von Ebner's gland might be an isoform. Propranolol and timolol, beta 1/beta 2-adrenergic receptor antagonists were not effective and the cholinergic receptor antagonist, atropine, was effective in only slightly reducing amylase secretion but not lingual lipase. Differential secretion of the two enzymes was observed for basal and stimulated secretion. Thus, exocytosis may not be the only pathway involved in SP-evoked protein secretion.

Fluid and protein secretion by the submandibular glands of weanling rats in response to cholinergic and peptidergic agonists at various doses

Fluid and protein secretion by the submandibular glands of 25-day-old rats were examined and compared in response to three cholinergic and four peptidergic sialogogues at various doses. All cholinergic and peptidergic agonists used were potent sialogogues for the submandibular glands of the weanling rats over the wide range of doses used. The cholinergic agonists, bethanechol and methacholine and the peptidergic agonists, substance P, substance PTyr8 and eledoisin-related peptide used intravenously, acted similarly to each other on the submandibular glands of the rats, late in the natural weaning period, but carbachol and physalaemin had slightly different effects. Of the peptidergic agonists, physalaemin was the most potent sialogogue among four tachykinins tested at the low dose. The types of protein secreted by the submandibular glands of the weanling rats in response to all sialogogues used here were typical of the beta-type. These results indicate that all agonists used could mainly stimulate the acinar cells of the submandibular glands of the weanling rats which have already fully developed functionally at this time.

Effects of substance P and substance P antagonists on rat salivary secretion

The intra-arterial infusion of substance P produced dose-related responses of both parotid and submandibular salivary secretion in anesthetized rats. The substance P-induced secretion in both glands was inhibited by the substance P analogues [D-Arg1, D-Trp7.9, Leu11]-substance P and [D-Arg1, D-Pro2, D-Trp7.9, Leu11]-substance P, but not by [D-Pro2, D-Trp7,9]-substance P. The profiles of protein and calcium levels obtained with substance P-induced salivary secretion for both glands were similar to those produced by acetylcholine stimulation and were not altered by the substance P analogues.