Yo Yoshida

Localization of neuronal-constitutive nitric oxide synthase and secretory regulation by nitric oxide in the rat submandibular and sublingual glands.

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

Basic Biological Sciences: Secretion and Re-absorption of Glucose in Rat Submandibular and Sublingual Saliva

Glucose permeation from blood to saliva appeared to follow the paracellular pathway in rat submandibular and sublingual glands, and the permeability was much higher in the sublingual than in the submandibular gland. The duct system re-absorbed glucose in the submandibular but not the sublingual gland. The glucose concentration in sublingual saliva was inversely related to the flow rate.Glucose permeation from blood to saliva appeared to follow the para cellular pathway in rat submandibular and sublingual glands, and the permeability was much higher in the sublingual than in the submandibular gland. The duct system re-absorbed glucose in the submandibular but not the sublingual gland. The glucose concentration in sublingual saliva was inversely related to the flow rate.

Activation of ascending antinociceptive system by vagal afferent input as revealed in the nucleus ventralis posteromedialis

Thalamic nociceptive neurons receiving afferent input from the tooth pulp (TP) were recorded from the nucleus ventralis posteromedialis proper (VPM) in cats anesthetized with urethane and chloralose. Effects of cervical vagus nerve stimulation on responses of TP neurons in the VPM were investigated. Twenty-one tooth pulp specific (TPS) and eight wide dynamic range (WDR) neurons with TP input were obtained from the periphery (shell region) of the posterior half of the VPM. Of these, many were also excited by electrical stimulation of trigeminothalamic tract (TTT) fibers in the trigeminal medial lemniscus. A conditioning-test paradigm was used to examine effects of vagal stimulation on responses of VPM neurons to electrical stimulation of TP and TTT. Inhibition of the responses was observed in 12 TPS and seven WDR neurons. Local anesthetic block of the mesencephalic periaqueductal gray (PAG) and/or nucleus raphe dorsalis (NRD) eliminated the inhibitory effects of vagal stimulation on the responses of both classes of TP neurons to TTT stimulation. In contrast, the inhibitory effects on responses to TP stimulation were insignificantly affected. These data suggest that vagal afferents can activate the ascending antinociceptive pathway from PAG/NRD onto VPM, in addition to activating the descending antinociceptive system acting upon the lower brain stem.

Role of amino acids in salivation and the localization of their receptors in the rat salivary gland

The distribution of gamma-aminobutyric acid (GABA) receptor subunits such as GABAAR-gamma 1 and GABAAR-gamma 2, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type receptor subunits such as GluR-1, GluR-2/3 and GluR-4, and N-methyl-D-aspartic acid (NMDA) type subunits such as NR1 were investigated by immunocytochemistry. Furthermore, the roles of these amino acids, GABA and glutamate, on salivation were analyzed in the rat submandibular and sublingual glands. Some similarities were observed in the distribution patterns of GABAA type receptors and AMPA receptors. In the submandibular ganglion cells, collecting ducts and striated ducts, these subunits were expressed strongly; however, there were some differences in their expression patterns between the submandibular and sublingual gland acinar cells. Since these receptor subunits were expressed in the acinar cell bodies of the submandibular gland, they were not expressed in the acinar cells but were expressed in the myoepithelial cells in the sublingual gland. On the other hand, no NR1 expression was observed. To examine the roles of GABA and glutamate in salivation, the submandibular and sublingual glands were perfused partially with Ringers solution via a facial artery to avoid systemic influence, and substrates were infused into the perfusion solution. No salivary secretion was evoked by GABA or glutamate infusion in the absence of electrical stimulation (2-3 V, 5 ms, 20 Hz). Salivary flow evoked by electrical stimulation of the chorda-lingual nerve caused significant inhibition by GABA (10(-6), 10(-5), 10(-4) and 10(-3) M) and the GABAAR agonist muscimol 10(-3) and 10(-6) M) (n = 6, P < 0.05). Such GABA-induced inhibition was antagonized by the GABAAR antagonists bicuculline (BCC; 10(-6) and 10(-3) M) and picrotoxin (PTX; 10(-6) and 10(-3) M). On the other hand, salivary flow evoked by electrical stimulation (8-10 V, 5 ms, 20 Hz) of the superior cervical ganglion (SCG) was not affected by GABA. While high doses of glutamate (10(-1) M) and NMDA (10(-1) M) showed no effects on salivary flow despite application of electrical stimulation, AMPA at a high concentration (10(-1) M) significantly inhibited salivary secretion (n = 6, P < 0.05). These studies revealed that inhibitory and excitatory amino acid receptors such as GABAA and AMPA type receptors are coexpressed in the rat salivary glands, and that GABA inhibits salivary secretion via GABAA receptors which may act with acetylcholine. However, the role of glutamate in salivation remains unclear despite the presence of AMPA type receptors. The present findings suggest that glutamate does not act alone but with other substances such as peptides and/or other amino acids.

Chorda-evoked opening of tight junctions in rat submandibular salivary acini demonstrated by microperoxidase

The permeability of these junctions from the interstitium to the lumen was examined by using an ultrastructural tracer, microperoxidase, in conjunction with electron microscopy. In the resting gland, the reaction product of microperoxidase was seen in the interstitial and intercellular spaces, but not within acinar lumina; thus the tight junction was impermeable to microperoxidase (junction closed). Intraductal injection of hypertonic sucrose solution (1000 mOsm; 30 microliters) caused a sustained elevation of the luminal pressure, indicating osmotic water flow into the lumen due to the presence of a hypertonic solution. In this gland no opening of the tight junctions was observed. In the chorda-stimulated gland, microperoxidase entered the lumen through the tight junctions, that is, they became permeable to microperoxidase (junction open). These findings suggest that chorda stimulation opens the acinar tight junctions and that the paracellular secretory pathway may be involved in the secretion of small molecules and water from the submandibular acini.

Effect of Streptozotocin Diabetes on Gingivitis in Plaque-susceptible Rats

The periodontal pocket probing depths of mandibular incisors of plaque-susceptible (Sus) rats, which spontaneously exhibit gingivitis with accumulation of plaque, were increased 20 days after injection of streptozotocin (70 mglkg, i.v.). The accumulated plaque weights were also increased in Sus rats with streptozotocin diabetes, and a positive correlation was found between the plaque weights and the pocket depths. Histological findings showed that this inflammatory reaction in gingival tissue was higher and more extensive in diabetic Sus rats than in control Sus rats. These findings suggest that the accumulated plaque is the important factor for the severe breakdown of gingival tissue in this experimental model.

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.

Transport of intravenously administered horseradish peroxidase into the rat submaxillary saliva.

Abstract When horseradish peroxidase (HPO) was administered i.v. to rats, peroxidase activity was detected histochemically in the lumen of the striated duct and in the basal portion of the striated duct cells of the submaxillary gland. On polyacrylamide-gel electrophoresis, two bands characteristic of HPO were identified in the submaxillary saliva. By Ouchterlonys test and immunoelectrophoresis, an antigen specific to HPO was detected in the saliva. It is concluded that intravenously administered HPO is taken up by the submaxillary gland cells and then transported into the saliva.

Cytochemical study of uptake of exogenous peroxidase by the rat submandibular salivary gland

Abstract When horseradish peroxidase (HPO) was administered intravenously to rats, its reaction product was detected cytochemically in the basal lamella surrounding the submandibular gland cells and in the intercellular spaces between the gland cells in the first few minutes after administration. HPO was also seen in vesicles in the cells of both the acini and duct elements. Ten min to 6 h after administration, HPO was found only in large membrane-bound vacuoles (probably lysosomes). It is concluded that exogenous HPO is rapidly incorporated into the cells by pinocytosis through the basal and lateral cell membranes, and then the pinocytotic vesicles are fused with lysosomes, and that exogenous HPO is transported into the gland lumen by lysosomes rather than by penetration through tight junctions.

1921 The functional properties of tooth pulp neurons in the caudal medulla oblongata of the cat

The medulla oblongata caudal to the obex was explored for neurons responsive to tooth pulp (TP) stimulation in cats. Four different subclasses of TP neurons were found. The latter included TP specific (TPS) neurons, trigeminal wide dynamic range (trigeminal WDR) neurons with TP input, trigeminal subnucleus reticularis ventralis (trigeminal SRV) neurons with TP input and convergent reticular formation (convergent RF) neurons with TP input. TPS neurons were located in the dorsal marginal rim of the trigeminal subnucleus caudalis, i.e., in the marginal layer or the outer zone of substantia gelatinosa. WDR neurons with TP input were found in the neck region of medullary dorsal horn which corresponds to the lateral part of subnucleus reticularis dorsalis (SRD). Trigeminal SRV neurons with TP input were located in the lateral part of SRV. Convergent RF neurons with TP input were found in the middle third of the caudal bulbar RF consisting of SRD and SRV. Both TPS neurons and WDR neurons with TP input included trigeminothalamic neurons as evidenced by the antidromic activation from the nucleus ventralis posteromedialis of the contralateral thalamus. A significant proportion of both trigeminal SRV and convergent RF neurons with TP input were antidromically activated by stimulation of the nucleus centralis lateralis of the contralateral thalamus. The former two subclasses may subserve the sensory-discriminative aspect of toothache, while the latter two subclasses, the emotional-motivational aspect.