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Background: Salivary gland function is controlled by the salivary reflex, whose efferent arm is composed by the parasympathetic and the sympathetic divisions of the autonomic nervous system. Parenchymal injury is the main salivary gland involvement of Sjögren's syndrome and head and neck radiotherapy, but neural damage has been reported as well. Recently an intraoral device for electrostimulation of the lingual nerve in vicinity to the lower third molar has been introduced. At this point this nerve carries efferent fibers for the innervation of the submandibular, sublingual and several minor salivary glands and afferent fibers of the salivary reflex. Therefore, excitation of these fibers potentially leads to increased secretion of all salivary glands. Thus, the study objective was to assess whether comprehensive neural activation by electrostimulation of the lingual nerve carries the potential to induce the regeneration of damaged salivary glands. Material and Methods: The device was tested on three patients with no collectable resting and stimulated secretion of saliva during a double blind, sham controlled period of two months and nine open-label months. Results: All three subjects developed the capacity to spit saliva, not only in direct response to the electrostimulation but also after free intervals without electrostimulation. In addition, their symptoms of dry mouth severity and frequency improved. Conclusions: This recovery is probably due to the combined effect of increase in secretory functional gland mass and regain of nervous control of the secretory elements and blood vessels. Both are phenomena that would contribute to gland regeneration. [ABSTRACT FROM AUTHOR]

Sardinian alcohol-preferring (sP) and Sardinian alcohol-non preferring (sNP) rats have been selectively bred for opposite alcohol preference and consumption. Aiming to verify possible differences at the proteomics level between sP and sNP rats, we investigated the salivary proteome by a a liquid chromatography–mass spectrometry top-down–bottom-up integrated approach. For this purpose, submandibular saliva was collected from alcohol-naive sP and sNP rats under isoprenaline stimulation. A total of 200 peptides and proteins were detected and quantified in the two rat lines, 149 of which were characterized in their naturally occurring structure. The data are available via ProteomeXchange with identifier PXD006997. Surprisingly, sP rats exhibited marked quantitative and qualitative differences with respect to sNP rats, namely higher levels of proteoforms originating from submandibular gland protein C, and from submandibular rat protein 2, as well as those of several unidentified peptides and proteins. sP rats expressed some proteins not detectable in sNP rats such as the glutamine and glutamic acid-rich protein (GRP)-CB. The isoform GRP-B, detectable in both rat lines, was more abundant in sNP rats. The submandibular saliva of sNP rats was also characterized by very high levels of GRP-B proteolytic peptides and rat salivary protein 1. Whether these differences could contribute to the opposite alcohol preference and consumption of sP and sNP rats is currently unknown and requires further investigation.

Two peptides (MW 1211.7 and 928.5 Da) were detected by RP–HPLC–ESI–MS analysis of parotid saliva secreted upon continuous parasympathetic stimulation. The peptide with the higher mass (PSPFr‐A) corresponded to the N‐terminal dodecapeptide (Fragment 1–12) of rat parotid secretory protein (PSP), while the peptide with the lower mass (PSPFr‐B) corresponded to the 4–12 fragment of the same protein. During stimulation, the PSPFr‐A secretion increased, while the PSPFr‐B secretion decreased (HPLC–ESI–MS). In the presence of cycloheximide, PSPFr‐A was not demonstrated, while the PSPFr‐B secretion decreased. In the presence of aprotinin, the PSPFr‐B secretion was almost abolished, while the PSPFr‐A secretion increased to higher levels than those observed in the absence of the inhibitor. In vitroperfusion, with artificial solution, of stimulated rat parotid glands excluded that the fragments were derived from the circulation. Neither peptide occurred in enriched granule preparations from unstimulated glands. The results suggest that at least two pathways – granular and vesicular – are responsible for the generation of the two peptides. PSPFr‐A is the first cleavage product in both pathways. PRPFr‐B is probably generated from granular PSPFr‐A only and, at the end of the granule mediated pathway, by the action of an enzyme of the serine protease class.

Nitric oxide (NO) is a likely parasympathetic non-adrenergic, non-cholinergic transmitter in parotid glands, since parasympathetic nervescontain NO-synthase. Parasympathetic stimulation (30 min, atropine+phentolamine+propranolol) increased the protein synthesis ([3H] leucine uptake) by 142% (10 Hz) and 200% (40 Hz). Surprisingly, neither the neuronal type NO-synthase inhibitor N-PLA, nor the unspecific inhibitor L-NAME reduced the response. Moreover, the parasympathetic non-adrenergic, non-cholinergic (40 Hz, 30 min)-evoked increase (65%) in mitotic activity ([3H] thymidine uptake) was unaffected by the NO-synthase inhibitors. Sympathetic nerveslack NO-synthase, yet inhibition of NO-generation reduced the β-adrenoceptor mediated response to sympathetic stimulation. Whereas the protein synthesis increased by 192% to stimulation (50 Hz, 1s every tenth s for 30 min) under just α-adrenoceptor blockade, the response was more than halved in the presence of N-PLA (to 86%) or L-NAME (to 91%). Furthermore, the β-adrenoceptor mediated increase in mitotic activity (122%) to sympathetic stimulation (20 Hz, 4 min every fifth min for 30 min), under α-adrenoceptor blockade, was reduced to 49% (N-PLA) and 47% (L-NAME). Pentagastrin(20 μg/kg, I. V. infused for one h) increased the protein synthesis by 17%. N-PLA prevented this increase but did not affect the basal protein, while cholecystokinin receptor blockers reduced both the basal protein synthesis (by 20%), and the pentagastrin-induced increase. Thus, implying that strong rather than weak stimuli of the cholecystokinin receptors activate neuronal type NO-synthase. Despite being of the neuronal type, the NO-synthase generating NO in response to stimulation of β-adrenoceptors or cholecystokinin receptors was probably of parenchymal origin.

The findings discussed in this paper mainly derived from studies on salivary glands, serving as model organs, indicate that the capacity to form the neurotransmitter acetylcholine, as judged by the activity of choline acetyltransferase, is influenced by the traffic of nerve impulses, as a long term effect. In the glands, choline acetyltransferase seems to be exclusively localized to the cholinergic nerves. In the postganglionic parasympathetic nerves of the glands, the activity of choline acetyltransferase decreases when the flow of secretory impulses in these nerves is abolished or reduced either by isolating the nerves from the central nervous system, surgically or pharmacologically, or by diminishing the reflex activation of the glands from the mouth. The opposite occurs when the reflex activation of the salivary glands is enhanced, i.e. the activity of choline acetyltransferase increases. Observations on various other organs are quoted in support of the view that the traffic of nerve impulses is of importance for the activity of the enzyme. An increase, in choline acetyltransferase activity also occurs in some salivary glands after sympathetic denervation. This puzzling observation is discussed in relation to impulse traffic. Increased nerve impulse traffic and collateral sprouting seem to be responsible for the rapid restitution of choline acetyltransferase activity from a low level in an organ partially deprived of its cholinergic nerve supply.

Abstract: Muscle activity of isolated muscle strips from the middle pharyngeal constrictor, the inferior pharyngeal constrictor, the cricopharyngeal muscle, and the cervical esophagus of the rabbit was studied in organ baths in response to drugs and electrical field stimulation. These muscles of the pharyngo-esophageal segment seem to lack an autonomic adrenergic and cholinergic innervation, as determined by responses to specific drugs. The nerve-evoked contractile responses of the two lower muscles of the segment were almost completely abolished by the curarelike drug gallamine, suggesting a somatic cholinergic nerve supply. However, in the two upper muscles, the major part of the response was resistant to gallamine, which suggests involvement of nonadrenergic, nonmuscarinic, nonnicotinic receptors in the transmission of nerve impulses in these muscles. These results suggest a differential innervation of the upper and lower pharyngeal muscles.

Abstract: The distribution of peptide-containing nerve fibers in the pharyngeal region of rabbits was studied by immunocytochemistry. Neuropeptide Y (NPY)-containing fibers were numerous around blood vessels and moderate in number among bundles of striated muscle fibers. A few NPY-containing fibers were seen around seromucous glands and beneath the epithelium. Nerve fibers containing vasoactive intestinal peptide (VIP) were numerous around seromucous glands and moderate in number around blood vessels, bundles of muscle, and in the subepithelial layer. A few nerve fibers containing substance P (SP) were seen around blood vessels, seromucous glands, among bundles of muscle, and in the subepithelial layer. Nerve fibers containing calcitonin gene-related peptide (CGRP) were numerous. They were distributed close to blood vessels, among bundles of muscle, in the subepithelial layer, and within the epithelium. A conspicuous finding was the occurrence of CGRP within motor end plates of striated muscle.

Ovariectomized virginal rabbits were treated with either estrogen or progesterone for 4 to 6 months. In vitro responses of muscle strips of the bladder and circular urethra were examined. Estrogen resulted in bladder contractions in response to noradrenaline and phenylephrine, whereas these agonists were without effect or evoked weak relaxations in castrated animals (and normals). Estrogen also caused a rightward shift of the frequency-contraction curve to nerve stimulation. Progesterone increased bladder sensitivity to contraction-evoking bethanechol. Contractile urethral responsiveness to bethanechol increased after both steroids. Urethral sensitivity to noradrenaline, evoking contraction, increased following estrogen. Further, estrogen abolished the marked relaxatory urethral response to nerve stimulation of castrated (and normal) rabbits and caused contraction only, which was abolished by a combination of α-adrenoceptor antagonists and scopolamine. When comparing the present results with those of other studies, it is evident that hormone-induced changes become manifest at an early stage. The present animal study gives support for the use of estrogen in the therapy of stress incontinence and, further, it provides no objections to the use of progesterone in combination with estrogen in this condition. This work was supported by grants from the Swedish Medical Research Council (project number 05927), Greta and Johan Kock’s Foundation and the Medical Faculty in Lund.

The circular muscle activity of the urethra of the male rat was isometrically measured in vitro in response to noradrenaline, phenylephrine and isoprenaline. The urethra was found to be supplied with both α- and β-adrenoceptors mediating contraction and relaxation, respectively. The substance 6-hydroxydopamine is known to cause a selective destruction of adrenergic nerves. In the present study 6-hydroxydopamine (100 mg/kg) was injected intravenously into a group of rats twice with a weekly interval. When the urethra was examined 2–3 weeks after the first injection a supersensitivity mediated both via α- and β-adrenoceptors was found to have developed, suggesting that the urethra of the male rat normally is under the influence of adrenergic activity. The findings are discussed in relation to denervation supersensitivity of the neurogenic bladder in man.

In rats, the distribution of nerve structures staining for NADPH-diaphorase, and showing immunoreactivities for nitric oxide synthase (NOS), tyrosine hydroxylase and various neuropeptides was studied in sensory ganglia (dorsal root, nodose and trigeminal ganglia), in sympathetic ganglia (superior cervical, stellate, coeliac-superior and inferior mesenteric ganglia), parasympathetic ganglia (sphenopalatine, submandibular, sublingual and otic ganglia), and in the mixed parasympathetic/ sympathetic ganglia (major pelvic ganglia). The coincidence of neuronal cell bodies with strong NOS-immunoreactivity and strong NADPH diaphorase reactivity was almost total. The relative proportions of NOS-immunoreactive nerve cell bodies were largest in parasympathetic ganglia and major pelvic ganglia followed by sensory ganglia. In sympathetic ganglia no NOS-immunoreactive neuronal cell bodies could be detected. In parasympathetic and major pelvic ganglia, there was a very significant neuronal co-localization of immunoreactivities for NOS and vasoactive intestinal polypeptide (VIP). This was almost total in major pelvic ganglia, in which NOS-/VIP-immunoreactive nerve cell bodies were separate from sympathetic (tyrosine hydroxylase-/neuropeptide Y-immunoreactive), suggesting that NOS-/VIP-immuno-reactive neurons might also be parasympathetic.